Climate Change and...
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Effects of Climate Change
Akselsson, C., Westling, O., Sverdrup, H., Gundersen, P. (2007). Nutrient and carbon budgets in forest soils as decision support in sustainable forest management. Forest Ecology and Management 238 (1-3): 167-174
ABSTRACT: Knowledge about the nutrient and carbon budgets in forest soils is essential to maintain sustainable production, but also in several environmental issues, such as acidification, eutrophication and climate change. The budgets are strongly influenced by atmospheric deposition as well as forestry. This study demonstrates how budget calculations for nitrogen (N), carbon (C) and base cations (BC) can be used as a basis for policy decisions on a regional level in Sweden.
The study was based on existing nutrient and C budget calculations on a regional scale in Sweden. The nutrient budgets have been calculated for each square in a national 5 km × 5 km net by means of mass balances including deposition, harvest losses, leaching, weathering (BC) and fixation (N). Scenarios with different deposition and forestry intensity have been run and illustrated on maps. A simplified C budget has been estimated by multiplying the N accumulation with the C/N ratio in the organic layer, based on the assumption that the C/N ratio in the accumulating organic matter is equal to the ratio in the soil organic matter pool. The budget approaches differ from earlier budget studies since they involve regional high resolution data, combine deposition and forestry scenarios and integrate different environmental aspects.
The results indicate that whole-tree harvesting will cause net losses of N and base cations in large parts of Sweden, which means that forestry will not be sustainable unless nutrients are added through compensatory fertilization. To prevent net losses following whole-tree harvesting, compensatory fertilization of base cations would be required in almost the whole country, whereas N fertilization would be needed mainly in the northern half of Sweden. The results further suggest that today's recommendations for N fertilization should be revised in southern Sweden by applying the southwest–northeast gradient of the N budget calculations. The C and N accumulation calculations show that C sequestration in Swedish forest soils is not an effective or sustainable way to decrease the net carbon dioxide emissions. A better way is to apply whole-tree harvesting and use the branches, tops and needles as biofuel replacing fossil fuels. This could reduce the present carbon dioxide emissions from fossil fuels substantially.
The study shows that high resolution budget calculations that illuminate different aspects of sustainability in forest ecosystems are important tools for identifying problem areas, investigating different alternatives through scenario analyses and developing new policies. Cooperation with stakeholders increases the probability that the research will be useful
ABSTRACT: Disturbances by fire and harvesting are thought to regulate the carbon balance of the Canadian boreal forest over scales of several decades. However, there are few direct measurements of carbon fluxes following disturbances to provide data needed to refine mathematical models. The eddy covariance technique was used with paired towers to measure fluxes simultaneously at disturbed and undisturbed sites over periods of about one week during the growing season in 1998 and 1999. Comparisons were conducted at three sites: a 1-y-old burned jackpine stand subjected to an intense crown fire at the International Crown Fire Modelling Experiment site near Fort Providence, Northwest Territories; a 1-y-old clearcut aspen area at the EMEND project near Peace River, Alberta; and a 10-y-old burned, mixed forest near Prince Albert National Park, Saskatchewan. Nearby mature forest stands of the same types were also measured as controls. The harvested site had lower net radiation (Rn), sensible (H) and latent (LE) heat fluxes, and greater ground heat fluxes (G) than the mature forest. Daytime CO2 fluxes were much reduced, but night-time CO2 fluxes were identical to that of the mature aspen forest. It is hypothesized that the aspen roots remained alive following harvesting, and dominated soil respiration. The overall effect was that the harvested site was a carbon source of about 1.6 g C m−2 day−1 , while the mature site was a sink of about −3.8 g C m−2 day−1 . The one-year-old burn had lower Rn, H and LE than the mature jackpine forest, and had a continuous CO2 efflux of about 0.8 g C m-2 day−1 compared to the mature forest sink of − 0.5 g C m−2 day−1 . The carbon source was likely caused by decomposition of fire-killed vegetation. The 10-y-old burned site had similar H, LE, and G to the mature mixed forest site. Although the diurnal amplitude of the CO2 fluxes were slightly lower at the 10-y-old site, there was no significant difference between the daily integrals (−1.3 g C m−2 day−1 at both sites). It appears that most of the change in carbon flux occurs within the first 10 years following disturbance, but more data are needed on other forest and disturbance types for the first 20 years following the disturbance event.
Ares, A., Terry, T.A., Piatek, K.B., Harrison, R.B., Miller, R.E., Flaming, B.L., Licata, C.W., Strahm, B.D., Harrington, C.A., Meade, R., Anderson, H.W., Brodie, L.C., Kraft, J.M. (2007). The Fall River long-term site productivity study in coastal Washington: Site characteristics, methods, and biomass and carbon and nitrogen stores before and after harvest. USDA Forest Service, Pacific Northwest Research Station: 1-88
DESCRIPTION: The Fall River research site in coastal Washington is an affiliate installation of the North American Long-Term Soil Productivity (LTSP) network, which constitutes one of the world's largest coordinated research programs addressing forest management impacts on sustained productivity. Overall goals of the Fall River study are to assess effects of biomass removals, soil compaction, tillage, and vegetation control on site properties and growth of planted Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco). Biomass-removal treatments included removal of commercial bole (BO), bole to 5-cm top diameter (BO5), total tree (TT), and total tree plus all legacy woody debris (TT+). Vegetation control (VC) effects were tested in BO, while soil compaction and compaction plus tillage were imposed in BO+VC treatment. All treatments were imposed in 1999. The preharvest stand contained similar amounts of carbon (C) above the mineral soil (292 Mg/ha) as within the mineral soil to 80-cm depth including roots (298 Mg/ha). Carbon stores above the mineral soil ordered by size were live trees (193 Mg/ha), old-growth logs (37 Mg/ha), forest floor (27 Mg/ha), old-growth stumps and snags (17 Mg/ha), coarse woody debris (11 Mg/ha), dead trees/snags (7 Mg/ha), and understory vegetation (0.1 Mg/ha). The mineral soil to 80-cm depth contained 248 Mg C/ha, and roots added 41 Mg/ha. Total nitrogen (N) in mineral soil and roots (13 349 kg/ha) was more than 10 times the N store above the mineral soil (1323 kg/ha). Postharvest C above mineral soil decreased to 129, 120, 63, and 50 Mg/ha in BO, BO5, TT, and TT+, respectively. Total N above the mineral soil decreased to 722, 747, 414, and 353 Mg/ha in BO, BO5, TT, and TT+, respectively. The ratio of total C above the mineral soil to total C within the mineral soil was markedly altered by biomass removal, but proportions of total N stores were reduced only 3 to 6 percent owing to the large soil N reservoir on site.
Bergeron, O., Margolis, H. A., Coursolle, C., Giasson, M. (2008). How does forest harvest influence carbon dioxide fluxes of black spruce ecosystems in eastern North America?. Agricultural and Forest Meteorology 148 (4): 537-548
ABSTRACT: Forest harvest is a major disturbance in the boreal forest of eastern North America and should significantly impact biosphere–atmosphere interactions at the regional scale. During a cooler, wetter year (2004) and a warmer, drier year (2005), we compared carbon dioxide (CO2 ) fluxes over a mature black spruce stand (EOBS) with a site that was harvested in 2000 (HBS00) and that had similar soil parent material, site fertility, climate, and pre-harvest species composition. During the study period, EOBS was C neutral (0–6 g C m−2 year−1 ), while HBS00 was a fairly strong C source (119–167 g C m−2 year−1 ). Averaged over both years, gross ecosystem productivity (GEP) was 101% higher at EOBS compared to HBS00 (636 g C m−2 year−1 versus 316 g C m−2 year−1 ), while ecosystem respiration (R) was 37% higher at EOBS (633 g Cm−2 year−1 versus 462 g C m−2 year−1 ). The mean between-site difference in annual NEP was six times greater than was the mean between-year difference, thus suggesting that the C budget of boreal black spruce forests is much more affected by developmental stage (i.e., stand age) than by between-year climate variability. Relative to the mature site, the harvested site had a more dynamic structure due to plant regrowth that induced greater between- and within-year variability in the response of GEP and R to environmental conditions over the 2-year study period. For example, maximum photosynthetic capacity was stable between years at EOBS (12.5μmol m−2 s−1 ), whereas it increased from 4.7 to 7.3μmol m−2 s−1 from 2004 to 2005 at HBS00. The photosynthetically active growing season started about a week later and finished a week earlier at HBS00 relative to EOBS. The earlier snowmelt at the harvested site did not promote an earlier start of the growing season at this site compared to the mature site. Although environmental conditions in spring have a significant influence on the annual C budget of mature sites, this does not seem to be the case for disturbed sites where mid-summer conditions are more important to the annual C balance.
ABSTRACT: These tables present current and historical area estimates of land use, land use change, forest management, and natural disturbance for forest lands of the U.S. We reconstruct portions of the history of U.S. forests of the 20th century using readily available and sometimes obscure public information collected by the U.S. Government, principally the U.S. Departments of Agriculture and Commerce. Much of the information is highly aggregated from large electronic data bases containing detailed records for recent decades, and some is summarized from printed tables of information contained in hundreds of government reports from earlier decades. The quality, consistency, and available detail of the information decrease back through time.
Where possible we follow the definitions published in Smith et al. (2001), also available on the internet at http://fia.fs.fed.us/. When combining data from different sources, we use a term “land use/land cover” to acknowledge that the available data sets are themselves based on somewhat inconsistent definitions. Many of the definitions have changed over time. Periodically, analysts revise older data sets to be consistent with changing definitions and standards for data collection. The most recent compilation of U.S. forest statistics by Smith et al. (2001) is an excellent example of the presentation of consistent historical estimates. In other cases where possible we have adjusted historical estimates to current standards to account for methodology changes.
The USDA Forest Service, Forest Inventory and Analysis (FIA) has conducted a comprehensive U.S. forest inventory since 1928. The USDA Natural Resources Conservation Service (NRCS) periodically estimates “land cover/use” for private lands of the U.S. in their National Resources Inventory (NRI) (Natural Resources Conservation Service 2000). The USDA Economic Research Service “Census of Agriculture” program has produced estimates of land use by State for various categories since 1945 (e.g. Daugherty 1995). Some relevant historical data are contained in a Bureau of Census compilation (U.S. Bureau of the Census, 1975), while other data are available in periodic reports by Agencies or special compilations requested by Congress (for example, USDA 1928).
Errors became evident in reconciling the different sources of information because of inconsistency in definitions, independent sampling frames, uncoordinated timing of data collection, and gaps and overlaps in scope of data collection. We estimate that we are missing information on about 6 million ha of Federal nonforest land, and that there is a double counting of about 13 million ha of private forest land and rangeland. These errors amount to about 2% of the total land area of the U.S.
ABSTRACT: Four plots from a mixed conifer forest were similarly cleared, burned, and replanted at various times over 17 years; a plot logged 79 years before sampling was used as a control. The plots had similar slope (2 to 15%, midslope position), aspect (south to southeast), and soil type (Holland series: mesic Haploxeralf; a Gray Brown Luvisol in the Canadian classification system). Twenty sites at each plot were sampled volumetrically by horizon to 20 cm below the organic–mineral soil boundary. Samples were analyzed for bulk density, organic C, and total N. There was an initial loss (15%) of organic C from the soil within 1 to 7 years, likely the result of oxidation (burning and decomposition) and erosion. For 17 years of forest regrowth, the soil continued to lose C (another 15%), probably owing to decomposition of slash material and possibly erosion, despite the slight accumulation of new litter and roots. After 80 years of regrowth, rates of carbon accumulation exceeded rates of loss, but carbon storage had declined and was not likely to recover to preharvest levels. Timber harvest and site preparation dramatically altered soil C and N distribution, in which C/N ratios after site preparation were initially high throughout the upper 20 cm. Subsequently, C/N ratios became lower with depth and with recovery age. Although stocks of C and N varied considerably among the plots and did not change consistently as a function of recovery age, the C/N ratios did vary systematically with recovery age. We hypothesize that the amount of C ultimately stored in the soil at steady state depends largely on N reserves and potentials, which appear to vary with erosion, intensity of burning, and site treatment.
Boerner, R EJ, Waldrop, T A, Shelburne, V B (2006). Wildfire mitigation strategies affect soil enzyme activity and soil organic carbon in loblolly pine (Pinus taeda ) forests. Canadian Journal of Forest Research 36 (12): 3148-3154
ABSTRACT: We quantified the effects of three wildfire hazard reduction treatments (prescribed fire, thinning from below, and the combination of fire and thinning), and passive management (control) on mineral soil organic C, and enzyme activity in loblolly pine (Pinus taeda L.) forests on the Piedmont of South Carolina. Soil organic C was reduced by thinning, either alone or with prescribed fire, and this effect persisted through the fourth post-treatment year. Fire also resulted in reduced soil organic C, but not until several years after treatment. Soil C/N ratio initially increased after fire, either alone or with thinning, but this difference did not persist. The activities of three soil enzymes (acid phosphatase, chitinase, and phenol oxidase) in the upper mineral soil were quantified as measures of microbial activity. During the fourth post-treatment year we observed significant stimulation of all three enzyme systems as a result of thinning or thinning and burning. Although the patterns of variation in acid phosphatase and chitinase activity among treatments were similar during the first and fourth post-treatment years, the first-year treatment effects were not statistically significant. Given the management objective of utilizing these stands for timber production, the increased potential for rapid nutrient turnover offered by thinning gives this approach advantages over prescribed fire; however, management for maximum long-term storage of soil C may be better facilitated by prescribed fire.
Bottcher, H., Freibauer, A., Obersteiner, M., Schulze, E.-D. (2008). Uncertainty analysis of climate change mitigation options in the forestry sector using a generic carbon budget model. Ecological Modelling 213 (1): 45-62
ABSTRACT: Industrialized countries agreed on a reduction of greenhouse gas emissions under the Kyoto Protocol. Many countries elected forest management activities and the resulting net balance of carbon emissions and removals of non-CO2 greenhouse gases by forest management in their climate change mitigation measures. In this paper a generic dynamic forestry model (FORMICA) is presented. It has an empirical basis. Several modules trace C pools relevant for the Kyoto Protocol and beyond: biomass, litter, deadwood and soil, and harvested wood products. The model also accounts for the substitution of fossil fuels by wood products and bioenergy.
FORMICA was used to first study the model sensitivity and uncertainty based on data from Thuringia, a federal state of Germany, to determine the major sources of uncertainty in carbon accounting at different levels of carbon pool aggregation (biomass, ecosystem, forestry sector and enhanced forestry sector including the accumulated substitution effect). Rotation length and maximum increment contributed most to uncertainty in biomass. The influence of the latter did not diminish with higher level of pool aggregation. Uncertainty in the enhanced forestry sector was to a smaller degree controlled by product and substitution related parameters. Relative uncertainty decreased with the level of aggregation and comprehensiveness of the carbon budget.
In a second step the model estimated the sink potential of the Thuringian forestry sector. The projected average biomass sink for the period of 2003–2043 of 0.6 t C ha−1 year−1 could be increased by 50% by broadening the perspective to the entire forestry sector, including substitution effects. A simulation of forest conservation on 20% of the forest area increased C fixation. However, even in the biomass C pool the expected C stock changes did not exceed the estimated uncertainty of 40%. A higher level of aggregation (i.e. the inclusion of soil and litter, product pool and substitution effects) decreases relative uncertainty but also diminishes differences between different management options. The analysis demonstrates that the choice of management mitigation options under an accounting scheme should include the impacts on forest products and of substitution effects.
ABSTRACT: Fire is the dominant factor affecting C and N losses from the semiarid forests of the eastern Sierra Nevada. As prescription fire becomes a best management practice, it is critical to develop an estimate of these fluxes. The objectives of this study were (i) to test and refine methods to estimate the volatilized C and N losses from the forest floor following fire, (ii) to investigate the interactions between O-horizon temperature and nutrient loss, and (iii) to assess measured N losses in the context of atmospheric N deposition, leaching, and N fixation. The quantities of C and N volatilized from the forest floor by prescription fire in the Sierra Nevada were measured using two different field-based methods: weight loss estimation and Ca/element ratio determination. Three sites were included in the study: Marlene, Sawtooth and Spooner. The weight method indicated C losses of 6.12, 7.39, and 17.8 Mg C ha-1 at the Sawtooth, Marlene, and Spooner sites, respectively. The ratio method indicated comparable C losses from the Sawtooth (6 Mg C ha-1 ) site, but greater losses at Marlene (16 Mg C ha-1 ) and Spooner (24 Mg C ha-1 ) sites. The weight method indicated N losses of 56.2, 60.8, and 362 kg N ha-1 , at the Sawtooth, Marlene, and Spooner sites, respectively. The ratio method indicated comparable N losses of 59.9 kg N ha-1 at the Sawtooth site, but considerably greater losses at Marlene (243 kg N ha-1 ), and Spooner (524 kg N ha-1 ) sites. The Ca-element method was preferred because of minimal needs for preburn sampling. Regardless of method, the estimated losses were significant, particularly for N, compared with deposition and leaching rates. Volatilization will represent the major mechanism for N loss from forest ecosystems of this region subjected to prescribed fire.
Concilio, A., Ma, S., Li, Q., LeMoine, J., Chen, J., North, M., Moorhead, D., Jensen, R. (2005). Soil respiration response to prescribed burning and thinning in mixed-conifer and hardwood forests.. Canadian Journal of Forest Research 35 (7): 1581-1591
ABSTRACT: The effects of management on soil carbon efflux in different ecosystems are still largely unknown yet crucial to both our understanding and management of global carbon flux. To compare the effects of common forest management practices on soil carbon cycling, we measured soil respiration rate (SRR) in a mixed-conifer and hardwood forest that had undergone various treatments from June to August 2003. The mixed-conifer forest, located in the Sierra Nevada Mountains of California, had been treated with thinning and burning manipulations in 2001, and the hardwood forest, located in the southeastern Missouri Ozarks, had been treated with harvesting manipulations in 1996 and 1997. Litter depth, soil temperature, and soil moisture were also measured. We found that selective thinning produced a similar effect on both forests by elevating SRR, soil moisture, and soil temperature, although the magnitude of response was greater in the mixed-conifer forest. Selective harvest increased SRR by 43% (from 3.38 to 4.82 µmol·m–2 ·s–1 ) in the mixed-conifer forest and by 14% (from 4.25 to 4.84 µmol·m–2 ·s–1 ) in the hardwood forest. Burning at the conifer site and even-aged harvesting at the mixed-hardwood site did not produce significantly different SRR from controls. Mean SRR were 3.24, 3.42, and 4.52 µmol·m–2 ·s–1 , respectively. At both sites, manipulations did significantly alter SRR by changing litter depth, soil structure, and forest microclimate. SRR response varied by vegetation patch type, the scale at which treatments altered these biotic factors. Our findings provide forest managers first-hand information on the response of soil carbon efflux to various management strategies in different forests.
ABSTRACT: Forestry has an important role to play as a provider of energy from renewable biomass and through the sequestration of carbon in biomass and soil. Forests are also habitats for a large number of species which are important for biodiversity. In some cases, these two roles may conflict. The aim of this study was to model the implications of specific environmental quality objectives on the potential of forestry to reduce net CO2 emissions by addressing interim targets 1 and 2 in the environmental quality objective, sustainable forests for Uppsala County and used this region as a case study. The carbon stock in the biomass, the substitution effect, and the economic consequences associated with six forest management scenarios were considered. The development for the scenarios was simulated at stand level using an empirical model. The results of the study showed that the shortest rotation period was preferable to mitigate net CO2 emissions since it resulted in more biomass that could replace fossil fuel. However, such a strategy might affect sustainable policies negatively. Increasing the extent of mixed stands could be a preferable strategy since it may achieve several objectives.
Fahey, T. J., Siccama, T. G., Driscoll, C. T., Likens, G. E., Campbell, J., Johnson, C. E., Battles, J. J., Aber, J. D., Cole, J. J., Fisk, M. C., Groffman, P. M., Hamburg, S. P., Holmes, R. T., Schwarz, P. A., Yanai, R. D. (2005). The biogeochemistry of carbon at Hubbard Brook. Biogeochemistry 75 (1): 109-176
ABSTRACT: The biogeochemical behavior of carbon in the forested watersheds of the Hubbard Brook Experimental Forest (HBEF) was analyzed in long-term studies. The largest pools of C in the reference watershed (W6) reside in mineral soil organic matter (43% of total ecosystem C) and living biomass (40.5%), with the remainder in surface detritus (14.5%). Repeated sampling indicated that none of these pools was changing significantly in the late-1990s, although high spatial variability precluded the detection of small changes in the soil organic matter pools, which are large; hence, net ecosystem productivity (NEP) in this 2nd growth forest was near zero (± about 20 g C/m2 -yr) and probably similar in magnitude to fluvial export of organic C. Aboveground net primary productivity (ANPP) of the forest declined by 24% between the late-1950s (462 g C/m2 -yr) and the late-1990s (354 g C/m2 -yr), illustrating age-related decline in forest NPP, effects of multiple stresses and unusual tree mortality, or both. Application of the simulation model PnET-II predicted 14% higher ANPP than was observed for 1996–1997, probably reflecting some unknown stresses. Fine litterfall flux (171 g C/m2 -yr) has not changed much since the late-1960s. Because of high annual variation, C flux in woody litterfall (including tree mortality) was not tightly constrained but averaged about 90 g C/m2 -yr. Carbon flux to soil organic matter in root turnover (128 g C/m2 -yr) was only about half as large as aboveground detritus. Balancing the soil C budget requires that large amounts of C (80 g C/m2 -yr) were transported from roots to rhizosphere carbon flux. Total soil respiration (TSR) ranged from 540 to 800 g C/m2 -yr across eight stands and decreased with increasing elevation within the northern hardwood forest near W6. The watershed-wide TSR was estimated as 660 g C/m2 -yr. Empirical measurements indicated that 58% of TSR occurred in the surface organic horizons and that root respiration comprised about 40% of TSR, most of the rest being microbial. Carbon flux directly associated with other heterotrophs in the HBEF was minor; for example, we estimated respiration of soil microarthropods, rodents, birds and moose at about 3, 5, 1 and 0.8 g C/m2 -yr, respectively, or in total less than 2% of NPP. Hence, the effects of other heterotrophs on C flux were primarily indirect, with the exception of occasional irruptions of folivorous insects. Hydrologic fluxes of C were significant in the watershed C budget, especially in comparison with NEP. Although atmospheric inputs (1.7 g C/m2 -yr) and streamflow outputs (2.7 g C/m2 -yr) were small, larger quantities of C were transported within the ecosystem and a more substantial fraction of dissolved C was transported from the soil as inorganic C and evaded from the stream as CO2 (4.0 g C/m2 -yr). Carbon pools and fluxes change rapidly in response to catastrophic disturbances such as forest harvest or major windthrow events. These changes are dominated by living vegetation and dead wood pools, including roots. If biomass removal does not accompany large-scale disturbance, the ecosystem is a large net source of C to the atmosphere (500–1200 g C/m2 -yr) for about a decade following disturbance and becomes a net sink about 15–20 years after disturbance; it remains a net sink of about 200–300 g C/m2 -yr for about 40 years before rapidly approaching steady state. Shifts in NPP and NEP associated with common small-scale or diffuse forest disturbances (e.g., forest declines, pathogen irruptions, ice storms) are brief and much less dramatic. Spatial and temporal patterns in C pools and fluxes in the mature forest at the HBEF reflect variation in environmental factors. Temperature and growing-season length undoubtedly constrain C fluxes at the HBEF; however, temperature effects on leaf respiration may largely offset the effects of growing season length on photosynthesis. Occasional severe droughts also affect C flux by reducing both photosynthesis and soil respiration. In younger stands nutrient availability strongly limits NPP, but the role of soil nutrient availability in limiting C flux in the mature forest is not known. A portion of the elevational variation of ANPP within the HBEF probably is associated with soil resource limitation; moreover, sites on more fertile soils exhibit 20–25% higher biomass and ANPP than the forest-wide average. Several prominent biotic influences on C pools and fluxes also are clear. Biomass and NPP of both the young and mature forest depend upon tree species composition as well as environment. Similarly, litter decay differs among tree species and forest types, and forest floor C accumulation is twice as great in the spruce–fir–birch forests at higher elevations than in the northern hardwood forests, partly because of inherently slow litter decay and partly because of cold temperatures. This contributes to spatial patterns in soil solution and streamwater dissolved organic carbon across the Hubbard Brook Valley. Wood decay varies markedly both among species and within species because of biochemical differences and probably differences in the decay fungi colonizing wood. Although C biogeochemistry at the HBEF is representative of mountainous terrain in the region, other sites will depart from the patterns described at the HBEF, due to differences in site history, especially agricultural use and fires during earlier logging periods. Our understanding of the C cycle in northern hardwood forests is most limited in the area of soil pool size changes, woody litter deposition and rhizosphere C flux processes.
J. Garcia-Gonzalo, H. Peltola, E. Briceño-elizondo, S. Kellomäki (2007). Changed thinning regimes may increase carbon stock under climate change: A case study from a Finnish boreal forest. Climatic Change V81 (3): 431-454
ABSTRACT: A physiological growth and yield model was applied for assessing the effects of forest management and climate change on the carbon (C) stocks in a forest management unit located in Finland. The aim was to outline an appropriate management strategy with regard to C stock in the ecosystem (C in trees and C in soil) and C in harvested timber. Simulations covered 100 years using three climate scenarios (current climate, ECHAM4 and HadCM2), five thinning regimes (based on current forest management recommendations for Finland) and one unthinned. Simulations were undertaken with ground true stand inventory data (1451 hectares) representing Scots pine (Pinus sylvestris ), Norway spruce (Picea abies) and silver birch (Betula pendula) stands. Regardless of the climate scenario, it was found that shifting from current practices to thinning regimes that allowed higher stocking of trees resulted in an increase of up to 11% in C in the forest ecosystem. It also increased the C in the timber yield by up to 14%. Compared to current climatic conditions, the mean increase over the thinning regimes in the total C stock in the forest ecosystem due to the climate change was a maximum of 1%; but the mean increase in total C in timber yield over thinning regimes was a maximum of 12%.
ABSTRACT: Forestry based carbon emissions offset projects have potential to both mitigate climate change and foster sustainable forest management. Degraded African tropical forests could sequester large amounts of additional carbon, but the lack of empirical data limits the feasibility of initiating carbon offset projects in many threatened forests. This study examines the potential to increase carbon stocks in the Kakamega National Forest of western Kenya, a threatened biodiversity hotspot and Kenya's only remaining rainforest. Carbon density values for indigenous forest and plantations were estimated based on forest inventory data from 95 randomized plots distributed throughout the forest. Total ecosystem carbon was estimated using allometric equations for tree biomass, destructive techniques for litter and herbaceous vegetation biomass, and Dumas combustion and spectroscopy for soils. Land cover maps for 1975, 1986, and 2000 were used to estimate both current carbon stocks and the influence of past land use changes. Mean carbon density in indigenous forest was 330 ± 65 Mg C/ha, greater than that of the forest's hardwood plantations (280 ± 77 Mg C/ha) and significantly greater that that of softwood plantations (250 ± 77 Mg C/ha). The distribution of carbon densities within the indigenous forest and the variation between plantation types suggest management practices could feasibly increase Kakamega's carbon stock. Deforestation between 1975 and 1986 and limited reforestation from 1986 to 2000 have resulted in a net loss of 0.4–0.6 Tg C. If this loss were reversed, the value of possible associated carbon credits dwarfs the current operational budget for managing and protecting the forest, even at low carbon prices. Additional income could help address resource needs of impoverished communities surrounding the forest and promote sustainable protection of Kakamega's high biodiversity.
Gough, C. M., Vogel, C. S., Harrold, K. H., George, K., Curtis, S. (2007). The legacy of harvest and fire on ecosystem carbon storage in a north temperate forest. Global Change Biology 13 (9): 1935-1949
ABSTRACT: Forest harvesting and wildfire were widespread in the upper Great Lakes region of North America during the early 20th century. We examined how long this legacy of disturbance constrains forest carbon (C) storage rates by quantifying C pools and fluxes after harvest and fire in a mixed deciduous forest chronosequence in northern lower Michigan, USA. Study plots ranged in age from 6 to 68 years and were created following experimental clear-cut harvesting and fire disturbance. Annual C storage was estimated biometrically from measurements of wood, leaf, fine root, and woody debris mass, mass losses to herbivory, soil C content, and soil respiration. Maximum annual C storage in stands that were disturbed by harvest and fire twice was 26% less than a reference stand receiving the same disturbance only once. The mechanism for this reduction in annual C storage was a long-lasting decrease in site quality that endured over the 62-year timeframe examined. However, during regrowth the harvested and burned forest rapidly became a net C sink, storing 0.53 Mg C ha−1 yr−1 after 6 years. Maximum net ecosystem production (1.35 Mg C ha−1 yr−1 ) and annual C increment (0.95 Mg C ha−1 yr−1 ) were recorded in the 24- and 50-year-old stands, respectively. Net primary production averaged 5.19 Mg C ha−1 yr−1 in experimental stands, increasing by < 10% from 6 to 50 years. Soil heterotrophic respiration was more variable across stand ages, ranging from 3.85 Mg C ha−1 yr−1 in the 6-year-old stand to 4.56 Mg C ha−1 yr−1 in the 68-year-old stand. These results suggest that harvesting and fire disturbances broadly distributed across the region decades ago caused changes in site quality and successional status that continue to limit forest C storage rates.
Hazlett, P. W., Gordon, A. M., Sibley, P. K., Buttle, J. M. (2005). Stand carbon stocks and soil carbon and nitrogen storage for riparian and upland forests of boreal lakes in northeastern Ontario. Forest Ecology and Management 219 (1): 56-68
ABSTRACT: The establishment of shoreline reserves (buffer strips) has guided riparian forest management in Ontario for many years. A riparian area is defined as the transitional zone between the aquatic and terrestrial environments and therefore is also known as the aquatic/terrestrial ecotone. While many functions of riparian forests have been recognized and well studied, less is known about their potential to sequester C and whether this potential differs from other areas in the boreal forest landscape. Increased harvesting pressure due to decreased wood supply in Ontario and debate about the effectiveness of the current reserve guidelines has resulted in a renewed interest in harvesting riparian forests. In this study riparian and upslope forest C and soil C and N storage were quantified for 21 lakes shorelines at the Esker Lakes Research Area, a boreal forest ecosystem in northeastern Ontario, Canada. Objectives were to compare the C and N storage potential of riparian forests with those of adjacent upland forests, and to examine the potential impacts of harvesting on C stocks in riparian zones of the boreal forest.
Riparian forests did not differ from upslope stands in terms of total aboveground overstory C storage although there were significant differences in stocking density and species composition. However, a greater proportion of total site C in riparian areas was stored in the overstory tree layer (>5 cm dbh) compared to upslope areas. Forest floor layers were deeper and stored more C and N in riparian forest stands in comparison to upslope stands. In contrast, mineral soil in upslope stands had greater C and N storage than mineral soil horizons within the riparian forest. As a result, the riparian organic horizons comprise a larger percentage of the overall soil storage of C and N than upslope layers. Currently practiced full-tree harvesting would result in a removal of approximately 76% of total aboveground C (17% of the ecosystem C) in upslope stands compared to 98% of total aboveground C (35% of the ecosystem C) in riparian forests. Selective or modified harvesting in riparian zones could decrease C removal to levels equal to that obtained by full-tree harvesting in upslope areas.
ABSTRACT: Accurate estimates of forest soil organic matter (OM) are now crucial to predictions of global C cycling. This work addresses soil C stocks and dynamics throughout a managed beechwood chronosequence (28–197 years old, Normandy, France). Throughout this rotation, we investigated the variation patterns of (i) C stocks in soil and humic epipedon, (ii) macro-morphological characteristics of humic epipedon, and (iii) mass, C content and C-to-N ratio in physical fractions of humic epipedon. The fractions isolated were large debris (>2000μm), coarse particular OM (cPOM, 200–2000μm), fine particular OM (fPOM, 50–200μm) and the mineral associated OM (MaOM, <50 μm).Soil C stocks remained unchanged between silvicultural phases, indicating a weak impact of this even-aged forest rotation on soil C sequestration. While humic epipedon mass and depth only slightly varied with beech development, C stocks in the holorganic layers were modified and the use of physical fractionation allowed us to discuss different aspect of quantitative and qualitative changes that occurred throughout the silvicultural rotation. Hence, changes in humic epipedon composition may be attributed to the modification of beech life-history traits with its maturation (growth vs. reproduction). Our results showed that C-POM can reached very high values (68%) in organo-mineral layers of older managed forest and that C-MaOM did not significantly change revealing the resistance of humified fractions of humic epipedon to logging and regeneration practices. C-to-N results indicated that N was probably not a limiting factor to litter degradation and explained our findings that OM did not accumulate in O horizons.This work confirms that forest harvesting and regeneration practices may have few effects on soil and humic epipedon C stocks, and that short- and long-term effects can be complex and may imply mechanisms with opposite effects.
Homann, P.S., Bormann, B.T., Boyle, J.R., Darbyshire, R.L., Bigley, R. (2008). Soil C and N minimum detectable changes and treatment differences in a multi-treatment forest experiment. Forest Ecology and Management 255 (5-6): 1724-1734
ABSTRACT: Detecting changes in forest soil C and N is vital to the study of global budgets and long-term ecosystem productivity. Identifying differences among land-use practices may guide future management. Our objective was to determine the relation of minimum detectable changes (MDCs) and minimum detectable differences between treatments (MDDs) to soil C and N variability at multiple spatial scales. The three study sites were 70–100-year-old coniferous forests in Washington and Oregon. Area- and volumetric-based soil measurements were made before implementation of 7 treatments on 2-ha experimental units, replicated in 3 or 4 blocks per site. In the absence of treatment effects, whole-site MDCs are 10% for mineral soil C and N masses and concentrations and 40% for O-horizon C and N masses. When treatment differences occur, MDDs are 40% for mineral soil and 150% for O-horizon. MDDs are reduced as much as two-thirds by evaluating change from pre- to post-treatment rather than only post-treatment values, and by pairing pre- and post-treatment measurements within small subplots. The magnitude of MDD reduction is quantitatively related to pre-treatment soil variability at multiple spatial scales, with the greatest reductions associated with the largest within-block:within-plot and within-plot:within-subplot variability ratios. These quantified benefits can be weighed against costs and challenges to make informed decisions when selecting the most appropriate sampling design.
DESCRIPTION: The subject of the effects of forest management activities on soil carbon is a difficult one to address, but ongoing discussions of carbon sequestration as an emissions offset and the emergence of carbon-credit-trading systems necessitate that we broaden and deepen our understanding of the response of forest-soil carbon pools to forest management. There have been several reviews of the literature, but hard-and-fast conclusions are still difficult to draw, since many of the studies reviewed were not designed specifically to address management effects on soil carbon, were conducted on a short timescale, and differ in the methodology employed.
ABSTRACT: We calculated carbon budgets for a chronosequence of harvested jack pine (Pinus banksiana Lamb.) stands (0-, 5-, 10-, and ~29-year-old) and a ~79-year-old stand that originated after wildfire. We measured total ecosystem C content (TEC), above-, and belowground net primary productivity (NPP) for each stand. All values are reported in order for the 0-, 5-, 10-, 29-, and 79-year-old stands, respectively, for May 1999 through April 2000. Total annual NPP (NPPT) for the stands (Mg C ha−1 yr−1 ±1 SD) was 0.9±0.3, 1.3±0.1, 2.7±0.6, 3.5±0.3, and 1.7±0.4. We correlated periodic soil surface CO2 fluxes (RS) with soil temperature to model annual RS for the stands (Mg C ha−1 yr−1 ±1 SD) as 4.4±0.1, 2.4±0.0, 3.3±0.1, 5.7±0.3, and 3.2±0.2. We estimated net ecosystem productivity (NEP) as NPPT minus RH (where RH was calculated using a Monte Carlo approach as coarse woody debris respiration plus 30–70% of total annual RS). Excluding C losses during wood processing, NEP (Mg C ha−1 yr−1 ±1 SD) for the stands was estimated to be −1.9±0.7, −0.4±0.6, 0.4±0.9, 0.4±1.0, and −0.2±0.7 (negative values indicate net sources to the atmosphere.) We also calculated NEP values from the changes in TEC among stands. Only the 0-year-old stand showed significantly different NEP between the two methods, suggesting a possible mismatch for the chronosequence. The spatial and methodological uncertainties allow us to say little for certain except that the stand becomes a source of C to the atmosphere following logging.
ABSTRACT: Soil carbon (C) pools are not only important to governing soil properties and nutrient cycling in forest ecosystems, but also play a critical role in global C cycling. Mulch and weed control treatments may alter soil C pools by changing organic matter inputs to the forest ecosystem. We studied the 12-month mulch and weed control responses on the chemical composition of soil organic C and the seasonal dynamics of water extractable organic C (WEOC), hot water extractable organic C (HWEOC), chloroform-released organic C (CHCl3-released C), and acid hydrolysed organic C (acid hydrolysable C) in a hardwood plantation of subtropical Australia. The results showed that compared with the non-mulch treatment, the mulch treatment significantly increased soil WEOC, HWEOC, and CHCl3-released C over the four sampling months. The weed control treatment significantly reduced the amount of HWEOC and CHCl3-released C compared with the no weed control treatment. Neither the mulch nor weed control treatment significantly affected soil acid hydrolysed organic C. There were no significant seasonal variations in soil WEOC, HWEOC, CHCl3-released C, and acid hydrolysed organic C in the hardwood plantation. Solid-state 13C nuclear magnetic resonance (NMR) spectroscopy was used to study the structural chemistry of soil C pools in hydrofluoric acid (HF) treated soils collected 12 months after the mulch and weed control treatments were applied. Overall, O-alkyl C was the dominant C fraction, accounting for 33–43% of the total NMR signal intensity. The mulch treatment led to higher signal intensity in the alkyl C spectral region and A/O-A ratio (the ratio of alkyl C region intensity to O-alkyl C region intensity), but lower signal intensity in the aryl C and aromaticity. Compared with the no weed control treatment, the weed control treatment reduced signal intensity in the aryl C and aromaticity. Together, shifts in the amount and nature of soil C following the mulch and weed control treatments may be due to the changes in organic matter input and soil physical environment.
R. B. Jackson, E. G. Jobbágy, R. Avissar, S. B. Roy, D. J. Barrett, C. W. Cook, K. A. Farley, D. C. le Maitre, B. A. McCarl, B. C. Murray (2005). Trading water for carbon with biological carbon sequestration. Science 310 (5756): 1944-1947
ABSTRACT: Carbon sequestration strategies highlight tree plantations without considering their full environmental consequences. We combined field research, synthesis of more than 600 observations, and climate and economic modeling to document substantial losses in stream flow, and increased soil salinization and acidification, with afforestation. Plantations decreased stream flow by 227 millimeters per year globally (52%), with 13% of streams drying completely for at least 1 year. Regional modeling of U.S. plantation scenarios suggests that climate feedbacks are unlikely to offset such water losses and could exacerbate them. Plantations can help control groundwater recharge and upwelling but reduce stream flow and salinize and acidify some soils.
Jandl, R., Lindner, M., Vesterdal, L., Bauwens, B., Baritz, R., Hagedorn, F., Johnson, D. W., Minkkinen, K., Byrne, K. A. (2007). How strongly can forest management influence soil carbon sequestration?. Geoderma 137 (3-4): 253-268
ABSTRACT: We reviewed the experimental evidence for long-term carbon (C) sequestration in soils as consequence of specific forest management strategies. Utilization of terrestrial C sinks alleviates the burden of countries which are committed to reducing their greenhouse gas emissions. Land-use changes such as those which result from afforestation and management of fast-growing tree species, have an immediate effect on the regional rate of C sequestration by incorporating carbon dioxide (CO2 ) in plant biomass. The potential for such practices is limited in Europe by environmental and political constraints. The management of existing forests can also increase C sequestration, but earlier reviews found conflicting evidence regarding the effects of forest management on soil C pools. We analyzed the effects of harvesting, thinning, fertilization application, drainage, tree species selection, and control of natural disturbances on soil C dynamics. We focused on factors that affect the C input to the soil and the C release via decomposition of soil organic matter (SOM). The differentiation of SOM into labile and stable soil C fractions is important. There is ample evidence about the effects of management on the amount of C in the organic layers of the forest floor, but much less information about measurable effects of management on stable C pools in the mineral soil. The C storage capacity of the stable pool can be enhanced by increasing the productivity of the forest and thereby increasing the C input to the soil. Minimizing the disturbances in the stand structure and soil reduces the risk of unintended C losses. The establishment of mixed species forests increases the stability of the forest and can avoid high rates of SOM decomposition. The rate of C accumulation and its distribution within the soil profile differs between tree species. Differences in the stability of SOM as a direct species effect have not yet been reported.
Jiang, Hong, Apps, Michael J., Peng, Changhui, Zhang, Yanli, Liu, Jinxun (2002). Modelling the influence of harvesting on Chinese boreal forest carbon dynamics. Forest Ecology and Management 169 (1-2): 65-82
ABSTRACT: Chinese boreal forests, geographically distributed in the Daxinganling Mountains of northeastern China, are the most southern part of the global boreal forest biome. The dominant species is larch (Larix gmelinii ) with other major species including birch (Betula platyphylla ), pine (Pinus sylvestris var.mongolica ) and oak (Quercus mongolica ). In this study, the terrestrial ecosystem process model CENTURY 4.0 was used to investigate the influence of different harvest disturbance regimes on the carbon stocks and fluxes of Chinese boreal forest ecosystem relative to a natural disturbance regime. Managed disturbance regime scenarios examined include harvesting intensity (no biomass removal (NBR), conventional harvesting (CH) and whole tree harvesting (WTH)) and rotation length (from 30 to 400 years). Field data were assembled from three forest regions (Xinlin, Tahe and Mohe), representing the northern, middle and southern parts of the Chinese boreal forest, respectively. The results presented in this study indicate that biomass, litter and soil carbon stocks (averaged over a rotation period) can be elevated significantly by suppression of all disturbances (NBR scenario) but are lowest under the most intense harvest scenarios (WTH). Harvest rotation length had a significant influence on carbon stocks (biomass, litter and soil carbon); the lowest simulated carbon stocks were found with the shortest rotations, and relatively higher stocks under longer rotations. Net primary production (NPP) decreased with increasing harvest intensity or decreasing rotation length. Net ecosystem production (NEP) decreased with decreasing harvest intensity or decreasing rotation length. NPP and NEP reach maximum values at rotation lengths of about 200 and 100 years, respectively. Observations and simulated data for ecosystem carbon stocks (biomass, litter and soil carbon) and carbon fluxes (NPP and NEP) in the southern region were slightly higher than those in the mid- and northern regions. The high productivity and biomass of the Chinese boreal forests relative to those of Canada, USA and Russia, are likely due to their southerly location: warm temperature and adequate precipitation create good conditions for forest development and growth. Nevertheless, the long history of forest use by human has resulted in much of the boreal forest in China landscape being in less than a primary state.
Johnson, D. W., Murphy, J. F., Susfalk, R. B., Caldwell, T. G., Miller, W. W., Walker, R. F., Powers, R. F. (2005). The effects of wildfire, salvage logging, and post-fire N-fixation on the nutrient budgets of a Sierran forest. Forest Ecology and Management 220 (1-3): 155-165
ABSTRACT: The effects of fire, post-fire salvage logging, and revegetation on nutrient budgets were estimated for a site in the eastern Sierra Nevada Mountains that burned in a wildfire in 1981. Approximately two decades after the fire, the shrub (former fire) ecosystem contained less C and more N than the adjacent forest ecosystem. Reconstruction of pre-fire nutrient budgets suggested that most C was exported in biomass during salvage logging and will not be recovered until forest vegetation occupies the site again. Salvage logging may have resulted in longer-term C sequestration in wood products than would have occurred had the logs been left in the field to decay, however. Reconstructed budgets suggested that most N was lost via volatilization during the fire rather than in post-fire salvage logging (assuming that foliage and O horizons were combusted). Comparisons of the pre-fire and present day N budgets also suggested that the lost N was rapidly replenished in O horizons and mineral soils, probably due to N-fixation by snowbush (Ceanothus velutinus Dougl.), the dominant shrub on the former fire site. There were no significant differences in ecosystem P, K, or S contents and no consistent, significant differences in soil extractable P or S between the shrub and forested plots. Exchangeable K+ , Ca2+ , and Mg2+ were consistently and significantly greater in shrub than in adjacent forested soils, however, and the differences were much larger than could be accounted for by estimated ash inputs. In the case of Ca, even the combustion of all aboveground organic matter could not account for more than a fraction of the difference in exchangeable pools. We speculate that the apparent large increased in soil and ecosystem Ca content resulted from either the release of Ca from non-exchangeable forms in the soil or the rapid uptake and recycling of Ca by post-fire vegetation.
Keller, C. K., White, T. M., O'Brien, R., Smith, J. L. (2006). Soil CO2 dynamics and fluxes as affected by tree harvest in an experimental sand ecosystem. Journal of Geophysical Research-Biogeosciences 111 (G03011): doi:10.1029/2005JG000157
ABSTRACT: Soil CO2 production is a key process in ecosystem C exchange, and global change predictions require understanding of how ecosystem disturbance affects this process. We monitored CO2 levels in soil gas and as bicarbonate in drainage from an experimental red pine ecosystem, for 1 year before and 3 years after its aboveground biomass was removed. Lack of physical disturbance, strict prevention of plant regrowth, and a comparison ecosystem without rooted plants facilitated isolation of the microclimatic and biochemical effects of instantaneous canopy removal and cessation of photosynthesis. Preharvest gas-phase CO2 levels fluctuated with growing-season soil temperature but reached their greatest levels (up to 10,000 ppmV) during late winter beneath snow and ice cover. This pattern, and the annual CO2 efflux of ~500 g C m−2 yr−1 , continued for 2 years following harvest; the efflux declined by half in the third year. The surprising continuity of preharvest and postharvest rates of soil CO2 production reflects the replacement of root respiration with microbial respiration of root and litter substrates of declining lability, but boosted by soil temperature increases. Mass balance is consistent with a bulk root+litter exponential decay time (−1/k) of 4–6 years, such that most of the subsurface biomass accumulated over 15 years of tree growth would be lost in a decade after the harvest. The preharvest bicarbonate C efflux, which was less than 0.1% of the gas-phase efflux, trebled after the harvest owing to elimination of evapotranspiration and consequent increases in drainage while soil CO2 levels remained high. A large fraction of this “hydrospheric” sink for atmospheric CO2 is attributed to weathering under high soil CO2 levels before spring snowmelt and soil-water flushing. These observations suggest that disturbance may enhance long-term chemical-weathering CO2 sinks.
ABSTRACT: This study was carried out to determine the effects of clear-cutting on soil CO2 efflux in a 42-year-old pine (Pinus densiflora S. et. Z.) stand. The variation of soil CO2 efflux rates with soil temperature, soil pH, soil moisture and soil organic carbon (C) content was measured monthly for 1 year in two pine plots; a clear-cut pine (CCP) and an uncut pine (UCP) plots. Mean soil CO2 efflux rates during the study period were significantly higher (P < 0.05) in CCP (0.52 g CO2 m−2 h−1 ) than in UCP (0.37 g CO2 m−2 h−1 ). High soil CO2 efflux rates in CCP were attributed to the change of soil temperature, soil pH, soil organic C and soil moisture content following canopy removal. In addition, soil temperature in CCP was significantly higher (1–3 °C) than in UCP except during winter (P < 0.05). Soil pH was also significantly higher (0.1–0.5 units) in CCP than in UCP (P < 0.05), suggesting a better environment for microbial or root growth activity. In contrast to soil temperature or soil pH, soil organic C and soil moisture content were significantly lower in CCP than in UCP (P < 0.05). The results indicated that the increased soil CO2 efflux rates in CCP compared with UCP could be due to the combined effect of high soil temperature, high soil pH, low soil organic C and soil moisture content.
ABSTRACT: Despite growing evidence for an effect of species composition on carbon (C) storage and sequestration, few projects have examined the implications of such a relationship for forestry and agriculture-based climate change mitigation activities. We worked with a community in Eastern Panama to determine the average above- and below-ground C stocks of three land-use types in their territory: managed forest, agroforests and pasture. We examined evidence for a functional relationship between tree-species diversity and C storage in each land-use type, and also explored how the use of particular tree species by community members could affect C storage. We found that managed forests in this landscape stored an average of 335 Mg C ha−1 , traditional agroforests an average of 145 Mg C ha−1 , and pastures an average of 46 Mg C ha−1 including all vegetation-based C stocks and soil C to 40 cm depth. We did not detect a relationship between diversity and C storage; however, the relative contributions of species to C storage per hectare in forests and agroforests were highly skewed and often were not proportional to species’ relative abundances. We conclude that protecting forests from conversion to pasture would have the greatest positive impact on C stocks, even though the forests are managed by community members for timber and non-timber forest products. However, because several of the tree species that contribute the most to C storage in forests were identified by community members as preferred timber species, we suggest that species-level management will be important to avoiding C-impoverishment through selective logging in these forests. Our data also indicate that expanding agroforests into areas currently under pasture could sequester significant amounts of carbon while providing biodiversity and livelihood benefits that the most common reforestation systems in the region – monoculture teak plantations – do not provide.
Kirschbaum, M.U.F., Guo, L. B., Gifford, R. M. (2008). Why does rainfall affect the trend in soil carbon after converting pastures to forests?: A possible explanation based on nitrogen dynamics. Forest Ecology and Management 255 (7): 2990-3000
ABSTRACT: When trees are planted onto former pastures, soil carbon stocks typically either remain constant or decrease, with decreases more common in regions with higher rainfall. We conducted a modelling analysis to assess whether those changes in soil carbon, especially the interaction with rainfall, could be understood through consideration of nitrogen balances. The study was based on simulations with the whole-system ecophysiological model CenW which allowed explicit modelling of both carbon and nitrogen pools and their fluxes through plants and soil organic matter.
We found that in a modelled coniferous forest without excess water input, total system nitrogen stocks remained similar to pre-forestation values because there were few pathways for nitrogen losses, and without biological nitrogen fixation or fertiliser inputs, gains were restricted to small inputs from atmospheric deposition. However, tree biomass and the litter layer accumulated considerable amounts of nitrogen. This accumulation of nitrogen came at the expense of depleting soil nitrogen stocks. With the change from input of grass litter that is low in lignin to forest litter with higher lignin concentration, organic-matter C:N ratios increased so that more carbon could be stored per unit of soil nitrogen which partly negated the effect of reduced nitrogen stocks. The increase in C:N ratios was initially confined to the surface litter layer because of slow transfer of material to the mineral soil. Over a period of decades, soil C:N ratios eventually increased in the soil as well.
Simulations with different amounts of precipitation showed that greater amounts of nitrogen were leached from systems where water supply exceeded the plants’ requirements. Reduced nitrogen stocks then caused a subsequent reduction in soil organic carbon stocks. These simulations thus provided a consistent explanation for the observation of greater losses of soil organic carbon in high-rainfall systems after converting pastures to forests. More generally, the simulations showed that explicit modelling of the nitrogen cycle can put important constraints on possible changes in soil-carbon stocks that may occur after land-use change.
ABSTRACT: Fire-prone forests in the American west are presently slated for extensive fuels reduction treatments, yet the effect on soil CO2 efflux rates, or soil respiration, has received little attention. This study utilizes the homogeneity of a Sierra Nevada ponderosa (Pinus ponderosa Dougl. ex P. & C. Laws)–Jeffrey pine (Pinus jeffreyi , Grev. & Balf.) plantation to investigate changes in soil respiration following mechanical shredding of understory vegetation, or mastication, in 2004; mastication coupled with prescribed burning in 2005; and burning alone also in 2005 as measured over the growing seasons from 2003 to 2005. Soil respiration, soil temperature and soil moisture were measured in two masticated stands which were burned the following year, and in one burned stand; the three of which were compared with two controls stands. Soil respiration response to treatments was detectable even though spatial variability within sites was high (coefficients of variation of 39–66%). Mastication produced short-term reductions in respiration rates, reduced soil moisture by 20%, and mitigated a year-to-year reduction in soil temperature evidenced by controls. Prescribed fire in masticated stands lowered soil respiration from 3.42 to 2.68μmol m−2 s−1 while fire in the untreated stand raised rates from 3.41 to 3.83μmol m−2 s−1 , although seasonal increases in control sites were greater than those in the untreated stand. Masticated then burned site soil moisture increased by 52% while soil temperature decreased over the span of the growing season. Microclimate variables were not consistently effective in explaining spatial trends. Exponential models using soil temperature and/or moisture to predict temporal trends in respiration were only significant in treated stands, suggesting that treatment implementation increased sensitivity to environmental factors. These results imply that fuels reduction practices in water-stressed forests may have important consequences for ecosystem carbon dynamics.
ABSTRACT: The extent of carbon (C) storage in forests and the change in C stocks after harvesting are important considerations in the management of greenhouse gases. We measured changes in C storage over time (from postharvest, postburn, year 5, year 10 and year 20) in logging slash, forest floors, mineral soils and planted lodgepole pine (Pinus contorta var.latifolia ) trees from six prescribed-burn plantations in north central British Columbia. After harvest, site C in these pools averaged 139 Mg ha-1 , with approximately equal contributions from mineral soils (0–30 cm), forest floors and logging slash. Together these detrital pools declined by 71 Mg C ha-1 , or 51% (28% directly from the broadcast burn, and a further 23% postburn), in the subsequent 20 yr. Postburn decay in logging slash was inferred by reductions in wood density (from 0.40 to 0.34 g cm-3 ), equal to an average k rate of 0.011 yr-1 . Losses in forest floor C, amounting to more than 60% of the initial mass, were immediate and continued to year 5, with no reaccumulation evident by year 20. Mineral soil C concentrations initially fluctuated before declining by 25% through years 10 and 20. Overall, the reductions in C storage were offset by biomass accumulation of lodgepole pine, and we estimate these plantations had become a net sink for C before year 20, although total C storage was still less than postharvest levels.
Lagergren, F., Lankreijer, H., Kucera, J., Cienciala, E., Molder, M., Lindroth, A. (2008). Thinning effects on pine-spruce forest transpiration in central Sweden. Forest Ecology and Management 255 (7): 2312-2323
ABSTRACT: This study analyses the effects of thinning on stand transpiration in a typical mixed spruce and pine forest in the southern boreal zone. Studies of transpiration are important for models of water, energy and carbon exchange, and forest management, like thinning, would change those processes. Tree transpiration was measured by the tissue heat-balance sapflow technique, on a reference plot and a thinning plot situated in a 50-year-old stand in central Sweden. Sapflow was measured during one season (1998) on both plots before thinning, to establish reference values. In winter 1998/1999 24% of the basal area was removed from the thinning plot. Thinning was done so as to preserve the initial species composition and the size distribution. The measurements continued after thinning during the growing seasons of 1999 and 2000. The climate showed remarkable differences between the 3 years; 1998 was wet and cool, with frequent rain, and the soil-water content was high throughout the year. In contrast, 1999 was dry and warm, and the soil-water content decreased to very low values, ca. 5–6% by volume. In 2000, the weather was more normal, with variable conditions. Stand transpiration was similar on both plots during the year before thinning; the plot to be thinned transpired 6% more than the reference plot. After thinning, transpiration was initially ca. 40% lower on the thinned plot, but the difference diminished successively. When the following drought was at its worst, the thinned plot transpired up to seven times more than the reference plot. During the second season after thinning, the thinned plot transpired ca. 20% more than the reference plot. The increased transpiration of the thinned plot could not be attributed to environmental variables, but was most probably caused by changes in biological factors, such as a fertilization effect.
Lasch, Petra, Badeck, Franz-W., Suckow, Felicitas, Lindner, Marcus, Mohr, Peter (2005). Model-based analysis of management alternatives at stand and regional level in Brandenburg (Germany). Forest Ecology and Management 207 (1-2): 59-74
ABSTRACT: The model-based analysis of the effects of management options at stand and regional levels on forest functions such as carbon storage and groundwater recharge provides a basis for optimisation of forest planning under global change. The physiologically based model 4C (‘FORESEE’—FORESt Ecosystems in a changing Environment) can be used to evaluate a broad variety of silvicultural treatments for mono- and mixed-species forest stands. In this study, we present the testing and evaluation of the 4C management submodel, using data from long-term experimental plots in selected stands in the Federal State of Brandenburg, Germany. Comparison of experimental data with model simulations, by means of diameter distributions, demonstrated that the applied thinning operations preserved the diameter distribution of the stands. 4C realistically described the effects of management options on stand dynamics as proved by long-term simulations. Furthermore, the investigation of the effects of management options, thinning intensity, and rotation length on carbon storage in biomass and soil, yield, and groundwater recharge showed the applicability of the model 4C for the evaluation of forest functions in managed forests.
We present the analysis of management effects on forest functions at a regional scale, based on a grid of forest monitoring sites (“Ökologische Waldzustandskontrolle”—ÖWK) in Brandenburg, which is mainly dominated by Scots pine (Pinus sylvestris L.). The model was applied at the sites with three management options under current climate and a climate change scenario (i.e., temperature increase of 1.4 °K by 2055). The results of 50-year simulation runs were analysed for forest growth units with respect to total carbon storage (Csum ) and groundwater recharge. More intensive management decreased the Csum after 50 years and slightly increased groundwater recharge. Climate change led to a reduction of groundwater recharge by about 40%, averaged over all sites. Csum was increased at some sites because of the extension of the growing season in spite of slight decreases in precipitation, but at several other sites, Csum decreased due to increased dryness. The question arises whether these negative effects of climate change can be minimised by adaptive management operations. In this study, we concluded that the potentials of adaptive management based on changes in rotation length and thinning is very limited in this region, which is characterised by poor sites and dry climatic conditions. We concluded that it is necessary to include forest transformation strategies in management impact analyses for forest planning under global change.
ABSTRACT: This paper describes four global-change phenomena that are having major impacts on Amazonian forests. The first is accelerating deforestation and logging. Despite recent government initiatives to slow forest loss, deforestation rates in Brazilian Amazonia have increased from 1.1 million ha yr–1 in the early 1990s, to nearly 1.5 million ha yr–1 from 1992–1994, and to more than 1.9 million ha yr–1 from 1995–1998. Deforestation is also occurring rapidly in some other parts of the Amazon Basin, such as in Bolivia and Ecuador, while industrialized logging is increasing dramatically in the Guianas and central Amazonia.
The second phenomenon is that patterns of forest loss and fragmentation are rapidly changing. In recent decades, large-scale deforestation has mainly occurred in the southern and eastern portions of the Amazon — in the Brazilian states of Pará, Maranho, Rondônia, Acre, and Mato Grosso, and in northern Bolivia. While rates of forest loss remain very high in these areas, the development of major new highways is providing direct conduits into the heart of the Amazon. If future trends follow past patterns, land-hungry settlers and loggers may largely bisect the forests of the Amazon Basin.
The third phenomenon is that climatic variability is interacting with human land uses, creating additional impacts on forest ecosystems. The 1997/98 El Niño drought, for example, led to a major increase in forest burning, with wildfires raging out of control in the northern Amazonian state of Roraima and other locations. Logging operations, which create labyrinths of roads and tracks in forsts, are increasing fuel loads, desiccation and ignition sources in forest interiors. Forest fragmentation also increases fire susceptibility by creating dry, fire-prone forest edges.
Finally, recent evidence suggests that intact Amazonian forests are a globally significant carbon sink, quite possibly caused by higher forest growth rates in response to increasing atmospheric CO2 fertilization. Evidence for a carbon sink comes from long-term forest mensuration plots, from whole-forest studies of carbon flux and from investigations of atmospheric CO2 and oxygen isotopes. Unfortunately, intact Amazonian forests are rapidly diminishing. Hence, not only is the destruction of these forests a major source of greenhouse gases, but it is reducing their intrinsic capacity to help buffer the rapid anthropogenic rise in CO2 .
Law, B. E., Thornton, P.E., Irvine, J., Anthoni, P.M., Van Tuyl, S. (2001). Carbon storage and fluxes in ponderosa pine forests at different developmental stages.. Global Change Biology 7 (7): 755-777
ABSTRACT: We compared carbon storage and fluxes in young and old ponderosa pine stands in Oregon, including plant and soil storage, net primary productivity, respiration fluxes, eddy flux estimates of net ecosystem exchange (NEE), and Biome-BGC simulations of fluxes. The young forest (Y site) was previously an old-growth ponderosa pine forest that had been clearcut in 1978, and the old forest (O site), which has never been logged, consists of two primary age classes (50 and 250 years old). Total ecosystem carbon content (vegetation, detritus and soil) of theO forest was about twice that of theY site (21 vs. 10 kg C m−2 ground), and significantly more of the total is stored in living vegetation at theO site (61% vs. 15%). Ecosystem respiration (Re) was higher at theO site (1014 vs. 835 g C m−2 year−1 ), and it was largely from soils at both sites (77% of Re). The biological data show that above-ground net primary productivity (ANPP), NPP and net ecosystem production (NEP) were greater at theO site than theY site. Monte Carlo estimates of NEP show that the young site is a source of CO2 to the atmosphere, and is significantly lower than NEP(O) by c. 100 g C m−2 year−1. Eddy covariance measurements also show that the O site was a stronger sink for CO2 than the Y site. Across a 15-km swath in the region, ANPP ranged from 76 g C m−2 year−1 at the Y site to 236 g C m−2 year−1 (overall mean 158 ± 14 g C m−2 year−1 ). The lowest ANPP values were for the youngest and oldest stands, but there was a large range of ANPP for mature stands. Carbon, water and nitrogen cycle simulations with the Biome-BGC model suggest that disturbance type and frequency, time since disturbance, age-dependent changes in below-ground allocation, and increasing atmospheric concentration of CO2 all exert significant control on the net ecosystem exchange of carbon at the two sites. Model estimates of major carbon flux components agree with budget-based observations to within ± 20%, with larger differences for NEP and for several storage terms. Simulations showed the period of regrowth required to replace carbon lost during and after a stand-replacing fire (O ) or a clearcut (Y ) to be between 50 and 100 years. In both cases, simulations showed a shift from net carbon source to net sink (on an annual basis) 10–20 years after disturbance. These results suggest that the net ecosystem production of young stands may be low because heterotrophic respiration, particularly from soils, is higher than the NPP of the regrowth. The amount of carbon stored in long-term pools (biomass and soils) in addition to short-term fluxes has important implications for management of forests in the Pacific North-west for carbon sequestration.
Maljanen, M., Nykanen, H., Moilanen, M., Martikainen, P. J. (2006). Greenhouse gas fluxes of coniferous forest floors as affected by wood ash addition. Forest Ecology and Management 237 (1-3): 143-149
ABSTRACT: Wood ash has been used to alleviate nutrient deficiencies of peat forests and to combat acidification of forest soils. Ash may change the activities of soil microbes, including those producing or consuming greenhouse gases, such as methane (CH4 ), nitrous oxide (N2 O) and carbon dioxide (CO2 ). We studied the effects of wood ash (loose wood ash originating from pulp mill or power plants) on the fluxes of CH4 , N2 O and CO2 in forests with mineral or peat soils in northern Finland. The ash doses were from 3 to 8 t ha−1 . Gas fluxes were measured with a closed chamber method from five recently fertilized experiments for 1 year after application of ash and from five long-term trials 14–50 years after application. Wood ash did not affect N2 O gas fluxes. In the long-term experiments, wood ash increased the soil CO2 production and the CH4 uptake and lowered the CH4 emissions.
ABSTRACT: Increasing concentrations of CO2 in the atmosphere have increased the value of sequestration and storage of C in forests. To maximize the value of this forest function, land managers require accounting systems to track the C stored in forests and in wood and fiber products. Accounting frameworks and data for quantifying C in forests and in wood and fiber products are generally available. In contrast, C emitted from fossil fuels utilized for silvicultural activities such as site preparation or fertilization, which are designed to increase C sequestration, have not been accounted for. The fossil fuel C emissions associated with silvicultural activities must be systematically evaluated to ensure that a net positive C balance results from activities ranging from planting to harvesting. The necessary data for evaluation are compiled from existing information. Utilizing the data, total C emissions from silvicultural activities for an intensive fiber farming operation of southern pine on a 25-year rotation is estimated to be <3 Mg C ha−1 . Increased C sequestration in soil or wood and fiber products in response to silvicultural treatments is simulated for 100 years to compare to the fossil fuel C emissions from silvicultural activities. The comparison demonstrates that the expected gains in C accumulation in soils of 16 Mg ha−1 over 100 years or gains due to increased harvest for paper products, also 16 Mg ha−1 , could each individually be largely balanced by silvicultural C emissions. On the other hand, C storage in wood products due to accelerated growth of trees to a saw log category might exceed the incurred C emissions by 3-fold (i.e., 35 Mg ha−1 ). If the combined C sequestration benefits from soil C accumulation, increased C storage in paper products, and storage in saw timber products could be captured these would outweigh the fossil fuel C emissions due to increased silvicultural activities.
ABSTRACT: Mixedwood forests are an ecologically and economically important forest type in central Canada, but the ecology of these forests is not as well studied as that of single-species dominated stands in the boreal forest. Northern boreal mixedwood forests have only recently been harvested and the effects of harvesting on carbon content in these stands are unknown. We quantified the carbon content and aboveground net primary production (NPP) for four different-aged mixedwood boreal forest stands in northern Manitoba, Canada. The stands included 11-, 18-, and 30-year-old stands that originated from harvesting and a 65-year-old fire-originated stand that typifies the origin of all northern boreal mixed-wood forests that are coming under management. Trees included black spruce (Picea mariana (Mill.) B.S.P.), jack pine (Pinus banksiana Lamb.), balsam poplar (Populus balsamifera L.), and quaking aspen (Populus tremuloides Michx.). Overstory biomass was estimated using species-specific allometric models that generally explained greater than 95% of the observed variation in biomass. Carbon content of the overstory vegetation was greatest in the 65-year-old stand and was 74% larger than the 11-year-old stand and showed a positive relationship with stand age (F1, 2=122.62, P=0.0081 R2 =0.99). The slope of mineral soil carbon did not differ significantly among stands (F1, 2=0.39, P=0.5956, R2=0.16). Coarse woody debris carbon content followed a U-shaped pattern among stands. Aboveground NPP differed by 24% between the youngest and oldest stand. Mean annual carbon accumulation and aboveground NPP rates of the mixedwood forests were on average two times greater than nearby relatively pure stands studied during the BOREAS (BOReal Ecosystem Atmospheric Study) project. The trends in the results, along with other field studies, suggest that harvesting does not significantly affect the total soil carbon content. The results of this study suggest that scientists should be cautious about extrapolating results from BOREAS stands to a broader region until more data on other forest types and regions are available.
McCarthy, D. R., Brown, K. J. (2006). Soil respiration responses to topography, canopy cover, and prescribed burning in an oak-hickory forest in southeastern Ohio. Forest Ecology and Management 237 (1-3): 94-102
ABSTRACT: Soil respiration (Rs ) is an important component of carbon loss from forest ecosystems. As forest management (e.g. prescribed burning) is becoming increasingly more common, it is important to understand the relationship between Rs and prescribed fire. Unfortunately, this relationship is still misunderstood due to the heterogeneity of physical and biological factors over the landscape and between ecosystems. To examine the effects of landscape position, canopy cover (CC), and prescribed burning on soil moisture, soil temperature, and Rs , while controlling for variation in soil properties, we utilized a randomized complete block (RCB) design with five treatments within each block. Each block consisted of five 2 m × 2 m treatment subplots: control, cool burn, hot burn, lime fertilization, and leaf litter removal. A total of 20 blocks were nested within a 2 × 2 factorial design with two effects, landscape position (upland or lowland) and canopy cover (100 or 60%). Rs , soil temperature, and soil moisture were measured monthly from June to November 2004. Repeated measures analysis of variance revealed significant effects of treatment and time on Rs . However, Rs was not significantly affected by prescribed fire, landscape position, or canopy cover. Soil temperature and moisture were significantly affected by landscape position, canopy cover, and time. By eliminating within-site variability between control and prescribed burning treatments, Rs rates were found to be unchanged in burn plots during the growing season following the fire. These results highlight the importance of environmental variability in determining the effects of prescribed fire on Rs rates.
FIRST PARAGRAPH: It is well known that intensive forest management practices can have significant effects on the biogeochemistry and biodiversity of forest ecosystems. For example, planting and thinning affects the structural biodiversity. Planting of nursery trees also determines the species (including mycorrhizae) and genetic diversity. Fertilization changes the nutrient balance, and thus competitive interactions. Clear-cutting combined with intensive soil preparation causes soil erosion, soil compaction, and losses of soil organic carbon and cations, which in turn affects biodiversity (e.g., Heinsdorf and Krauß 1974; Bormann and Likens 1979; Covington 1981; Heinsdorf 1986; Black and Harden 1995; Apps and Price 1996; Nyland 1996; Jurgensen et al. 1997; Rollinger et al. 1998;Worrell and Hampson 1997; Prescott et al. 2000b; Quesnel and Curran 2000; Johnson and Curtis 2001; Block et al. 2002). However, our knowledge about the interactions of biodiversity with silviculture and site-specific factors and the role of biodiversity in biogeochemical cycles is still very limited.
ABSTRACT: The objectives of this study were to quantify the effects of prescribed fire on forest floor C and nutrient content, soil chemical properties, and soil leaching in a Jeffrey pine (Pinus jeffreyi [Grev. and Balf.]) forest in the eastern Sierra Nevada Mountains of California. The study included a prescribed fire and three timber harvest treatments: whole-tree (WT) thinning, cut-to-length (CTL) thinning, and no harvest (CONT). Prescribed fire resulted in significant decreases in forest floor C (-8 to -23 mg ha-1 , or 39% to 61% decrease), N (-114 to -252 kg ha-1 , or -31% to 51% decrease), S (0 to -15 kg ha-1 , or 0% to 48% decrease), and K (-3 to -45 kg ha-1 , or 12% to 51% decrease) contents but no significant change in Ca or Mg contents. In each case, the decreases were greatest in the CTL treatment, where slash accumulation before burning was greatest. Burning caused statistically significant effects on soil total nitrogen, C:N ratio, pH, water-extractable ortho-P, and water-extractable SO4 2- in some cases, but these effects were generally small, inconsistent among harvest treatments and horizons, and in the case of ortho-P much less than the temporal variation in both burned and unburned plots. There were no statistically significant effects of burning on total C, Bray-extractable P, bicarbonate-extractable P, and exchangeable Ca2+ , K+ , or Mg2+ . Burning had no significant effect on soil solution pH, ortho-P, SO4 2- , NO3 - , or NH4 + as measured by ceramic cup lysimeters and no effect on the cumulative leaching of ortho-P, NO3 - , or NH4 + as measured by resin lysimeters. Burning had no effect on needle weight or nutrient contents as measured by the vector analysis. We conclude that prescribed fire had minimal effects on soils or water quality at this site, and that the most ecologically significant effect was the loss of N from the forest floor.
Nakane, K., Lee, N.-J. (1995). Simulation of soil carbon cycling and carbon balance following clear-cutting in a mid-temperate forest and contribution to the sink of atmospheric CO2 . Vegetatio 121 (1-2): 147-156
ABSTRACT: A simulation model of soil carbon cycling was developed based on the data observed in a mid-temperate forest in Yoshiwa, Hiroshima Prefecture, Japan, and soil carbon cycling and carbon budget in a mature forest stand and following clear-cutting were calculated on a daily basis using daily air temperature and precipitation data. The seasonal change in the amount of the A0 layer was characterized by a decrease from spring to autumn due to rapid decomposition of litter, and recovery in late autumn due to a large litterfall input. There was little change in the amount of humus in mineral soil. These estimates coincides closely with those observed in the field. Most flow rates and the accumulation of soil carbon decreased very markedly just after clear-cutting. The A0 layer reached its minimum in 10 years, and recovered its loss within 50–60 years after cutting. A large loss of carbon was observed just after cutting, but the balance changed from negative to positive in 15 years after cutting. The total loss of soil carbon following cutting recovered within 30 years, and nearly the same amount of carbon as that stocked in the timber before harvesting accumulated 70–80 years after cutting. The calculation by the simulation model was made using the assumption that the increase in atmospheric CO2 promoted the primary production rate by 10% over the last three decades. The result suggests that about 8 t C ha-1 was sunk into soils of the mid-temperate forest over the same period. It indicates that forest soils may be one of the main sinks for atmospheric CO2 .
Neilson, E.T., MacLean, D.A., Meng, F.-R., Arp, P.A. (2007). Spatial distribution of carbon in natural and managed stands in an industrial forest in New Brunswick, Canada. Forest Ecology and Management 253 (1-3): 148-160
ABSTRACT: Industrial forest could be managed to enhance carbon (C) sequestration together with other ecological and socio-economic objectives. However, this requires quantifying C dynamics of all major forest types within the management area, over the whole forest rotation. We used data from permanent sample plots and temporary forest development survey plots to generate volume yield curves and used the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) to estimate C yield and dynamics over a rotation for major forest types in northern New Brunswick, Canada. We compared C yields of natural versus managed and hardwood versus softwood forest under different silviculture treatments over the entire rotation. Carbon in 40–80-year-old and > 80-year-old tolerant hardwood stands averaged about 115 and 130–142 t ha−1, respectively, while softwood spruce (Picea sp.)–balsam fir (Abies balsamea (L.) Mill.) 40–80 and > 80 years old averaged 90 and 88–94 t C ha−1 . Among 10 stand types, total C ranged from 50 to 109 t ha−1 at age 50 years, 92–138 t ha−1 at age 100, and 79–145 t ha−1 at age 150 years. C in most stand types declined from age 100 to 150 years, except for eastern white cedar (Thuja occidentalis L.), sugar maple (Acer saccharum Marsh.) and yellow birch (Betula alleghaniensis Britton). At age 100 years, planted softwood stands had 94–135 t ha−1 , versus 92–117 t ha−1 for natural softwoods and 127–138 t ha−1 for natural hardwoods. Planted white spruce (Picea glauca (Moench) Voss) and natural sugar maple and yellow birch sequestered the most C. The total C (above and belowground biomass and deadwood, excluding soil carbon) on the 428,000 ha test landbase was 35 million tonnes, or an average of 82 t ha−1 .
Palosuo, T., Peltoniemi, M., Mikhailov, A., Komarov, A., Faubert, P., Thurig, E., Lindner, M. (2008). Projecting effects of intensified biomass extraction with alternative modelling approaches. Forest Ecology and Management 255 (5-6): 1423-1433
ABSTRACT: The effect of intensified biomass extraction on forest ecosystems is a timely question since harvest residues are increasingly utilised to produce energy and the impacts of the changed management practises are not always well understood. We compared two different modelling approaches, the MOTTI-YASSO and the EFIMOD-ROMUL model combinations, with respect to the simulated impacts of the biomass extraction in final felling on subsequent biomass and soil carbon stocks. Simulations following the latest silvicultural recommendations over a rotation were made for six Finnish forest sites varying in fertility, tree species and latitude. Model-projected effect of the intensified biomass extraction was larger with EFIMOD-ROMUL than with MOTTI-YASSO. The soil model ROMUL projected slower decomposition of organic matter than YASSO at all studied sites, which made the effect of biomass extraction on soil larger with EFIMOD. The process-based model EFIMOD-ROMUL includes feedback from soil nutrient status to productivity. With EFIMOD-ROMUL, the intensified biomass extraction decreased slightly the simulated growth of the forests and thereby the biomass carbon stock and litter input to the soil. With the empirical MOTTI model, the intensity of the simulated biomass extraction did not affect forest growth. Our results underline the importance of the selection of the modelling approach when projecting the potential effects of forest management practises on forest carbon balance.
Sartori, Fabio, Lal, Rattan, Ebinger, Michael H., Eaton, James A. (2007). Changes in soil carbon and nutrient pools along a chronosequence of poplar plantations in the Columbia Plateau, Oregon, USA. Agriculture, Ecosystems & Environment 122 (3): 325-339
ABSTRACT: Establishment of short-rotation woody crop (SRWC) plantations for meeting the demand of wood and bioenergy production necessitates reclamation of agricultural lands and desert soils, such as those in the southern Columbia Plateau of Oregon, USA. The effects of plantation management on soil carbon (C) storage and nutrient concentration were evaluated, using a chronosequence of poplar (Populus spp.) stands on soils of eolian origin (Xeric Torripsamments). Stands of ages 1, 3, 4, 7, 9, and 10 years (n = 3 per stand age), as well as adjacent agricultural and desert lands, were compared based on soil C, inorganic C (SIC), total nitrogen (N), and nutrient concentrations within the 0- to 50-cm soil depth. The 7- through 10-year-old stands that were in a first-rotation cycle were irrigated and fertilized. The 1- through 4-year-old stands in a second-rotation cycle received a mulch application treatment in addition to the irrigation and fertilization treatments. At age 11 years, the projected plantation C (147.5 Mg ha-1 ) accumulated almost entirely in the aboveground biomass (62.2%), forest floor (24.3%), and roots (11.7%). There were no significant increases in the mineral soil C and N pools with stand age, despite the presence of increasing trends within the surface layer. The accumulation of the mineral soil C pool (~1.8%), from the first- (23.5 +/- 1.7 Mg C ha-1 ) to the second-rotation stands (26.3 +/- 3.5 Mg C ha-1 ), was partially offset by a loss of SIC due to irrigation. The SIC pool had a decreasing trend, which was related to dissolution of calcite along the soil profile, from the first- (16.7 +/- 3.4 Mg C ha-1 ) to the second-rotation stands (8.4 +/- 5.0 Mg C ha-1 ). Soil pH (r > 0.6) and exchangeable acidity (r = -0.5) patterns were dependent upon the concentration of exchangeable Ca2+ . Soil Mg2+ and K+ concentrations were correlated with soil C concentration in the surface layer (r = 0.5). In coarse-textured soils, a decadal time scale was insufficient to measure significant changes in the mineral soil C pool. Carbon benefits may be gained, however, in aboveground (tree and forest floor) and belowground (roots) biomass accumulations. SRWC plantations are an effective land-use option to restore degraded lands of arid regions.
Scarascia-Mugnozza, G., De Angelis, P., Sabatti, M., Calfapietra, C., Miglietta, F., Raines, C., Godbold, D., Hoosbeek, M., Taylor, G., Polle, A., Ceulemans, R. (2005). Global change and agro-forest ecosystems: adaptation and mitigation in a FACE experiment on a poplar plantation. Plant Biosystems 139 (3): 255-264
ABSTRACT: The objective of this research was to determine the functional responses of a cultivated, agro-forestry system, namely a poplar plantation, to actual and future atmospheric CO2 concentrations. Hence, this research has combined a fast growing, agro-forestry ecosystem, capable of elevated biomass production, with a large-scale Free Air Carbon Enrichment (FACE) system, one of the few available in the European Union on a forest tree stand. The FACE facility is located close to a natural CO2 source and is drawing scientists from several European countries, and from other continents, to closely cooperate and combine their scientific efforts on the same experimental system. Furthermore, this FACE apparatus utilizes a novel technology, originally developed by Italian institutions, based on the release into the atmosphere, at sonic velocity, of pure CO2 instead of an air-CO2 mixture. The research activities conducted at the POPFACE site, on the responses of the tree plantation to future atmospheric conditions, have integrated observations at the leaf level, such as photosynthesis, respiration and transpiration, with measures carried out at the whole-tree and stand scale, such as canopy architecture, light interception and biomass production. Finally, the ecosystem dimension has also been analysed by studying root productivity and soil processes, host – parasite interactions, and carbon sequestration throughout a rotation cycle of the stand.
ABSTRACT: Secondary forests are becoming an increasingly important tropical landscape component with the potential to provide environmental services such as soil carbon storage. Substantial losses of soil carbon can occur with tropical forest conversion to pasture, but stocks can sometimes be restored with the development of secondary forest. Few studies have taken advantage of shifts in vegetation from C4 to C3 communities to determine soil carbon turnover following secondary forest development on pasture. Because trees quickly colonize abandoned pastures in northeastern Costa Rica, we expected to find evidence of increased soil carbon storage and gradual soil carbon turnover following pasture abandonment. Three early successional and nine late successional secondary sites ranging in age from 2.6 to 33 years, as well as four pastures were used in this study. At each site, mineral soil samples up to 30 cm depth were collected from three plots to determine bulk density, percent soil carbon, and stable carbon isotope values (d13 C). Thed13 C of soil respired CO2 was also determined at each site. Contrary to expectations, soil carbon storage did not increase with secondary forest age and was unrelated to increases in aboveground carbon storage. However, pastures stored 19% more carbon than early and late successional sites in the top 10 cm of mineral soil, and successional sites stored 14-18% more carbon than pastures between 10 and 30 cm.d13 C data indicated that most pasture-derived soil carbon in the top 30 cm of soil turned over within 10 years of pasture abandonment and subsequent colonization by trees. Overall, these data indicate that total soil carbon storage remains relatively unchanged following land use transitions from pasture to secondary forest. This is likely due to the presence of large passive pools of mineral-stabilized soil carbon in this region of Costa Rica. The contribution of these forests to increased carbon storage on the landscape is primarily confined to aboveground carbon stocks, though other environmental services may be derived from these forests. In the context of global carbon accounting, it appears that future carbon credits may be best applied to aboveground carbon storage in secondary forests regrowing on soils with large mineral-stabilized soil carbon pools.
Schmid, S., Thurig, E., Kaufmann, E., Lischke, H., Bugmann, H. (2006). Effect of forest management on future carbon pools and fluxes: A model comparison. Forest Ecology and Management 237 (1-3): 65-82
ABSTRACT: Currently, there is a strong demand for estimates of the current and potential future carbon sequestration in forests, the role of management practices, and the temporal duration of biotic carbon sinks. Different models, however, lead to different projections. Model comparisons allow us to assess the range of potential ecosystem responses, and they facilitate the detection of the strengths and weaknesses of particular models. In this study, the empirical, individual-based forest models MASSIMO, the semi-empirical individual-based forest models SILVA – both combined with the soil model YASSO – and the process-based, biogeochemical model Biome-BGC were used to assess the above- and belowground carbon pools and net fluxes of several forested regions in Switzerland for the next 100 years under four different management scenarios: (1) the current harvest amounts were used, (2) harvest was intensified by reducing the amount of large tree dimensions, (3) harvest was reduced to a minimum by only maintaining the protection function in mountain forests and avoiding pests and diseases, and (4) harvest was adjusted to achieve maximum sustainable growth. The results show that the three models projected similar patterns of net carbon fluxes. The models estimated that in the absence of large-scale disturbances the forest biomass and soil carbon can be increased, particularly under scenario 2, and therefore, forests can be used as carbon sinks. These sinks were estimated to last for a maximum of 100 years. Differences between the management scenarios depend on the time period considered: either net carbon fluxes are maximized at a short term (30–40 years) or at a longer term (100 years or more). In contrast to the similar carbon fluxes, some carbon pools projected by the models differed strongly. These differences in model behaviour can be attributed to model-specific responses to the strongly heterogeneous Swiss climate conditions and to different model assumptions. To find the optimum strategy in terms of not only maximizing carbon sequestration but climate protection, it is essential to account for wood-products and particularly substitution of fossil fuel in the model simulations.
ABSTRACT: The Kyoto protocol aims to reduce carbon emissions into the atmosphere. Part of the strategy is the active management of terrestrial carbon sinks, principally through afforestation and reforestation. In their Perspective, Schulze et al. argue that the preservation of old-growth forests may have a larger positive effect on the carbon cycle than promotion of regrowth.
ABSTRACT: A process-based model BIOME-BGC designed for simulation of biogeochemical element cycling in terrestrial ecosystems was prepared for application to managed forest ecosystems in temperate Europe. New routines were implemented that permit specification of thinning, felling and species change when planting new forest. Other changes were implemented to water cycling routines, specifically to precipitation and evaporation, simulation of industrial nitrogen deposition and fine roots mortality. The major aim of the paper was to conduct a sensitivity analysis of the adapted model. We specifically analysed the effects of site and eco-physiological parameters on the modeled state variables (carbon pools in biomass, litter and soil and net primary production (NPP)). The analysis revealed a high sensitivity of all tested variables to the following site parameters: total precipitation, rooting depth, sand fraction (for sandy soils only), ambient CO2 and parameters of nitrogen input. Similarly, the tested variables were shown to be highly sensitive to the following eco-physiological parameters: leaf and fine root C:N ratio, new stem C to new leaf C ratio, new fine root C to new leaf C ratio, specific leaf area, maximum stomatal conductance, fire mortality and fraction of N in Rubisco (specifically for deciduous species). Additionally, the whole plant mortality had a high effect on carbon pools, but a small effect on NPP.
ABSTRACT: Carbon sequestered in biomass is not necessarily stored infinitely, but is exposed to human or natural disturbances. Storm is the most important natural disturbance agent in Swiss forests. Therefore, if forests are taken into account in the national carbon budget, the impact of windthrow on carbon pools and fluxes should be included. In this article the forest scenario model MASSIMO and the soil carbon model YASSO were applied to assess the effect of forest management and an increased storm activity on the carbon sequestration in Swiss forests. First, the soil model was adapted to Swiss conditions and validated. Second, carbon fluxes were assessed applying the two models under various forest management scenarios and storm frequencies. In particular, the influence of clearing after a storm event on the carbon budget was analyzed. The evaluation of the model results showed that the soil model reliably reproduces the amount of soil carbon at the test sites. The simulation results indicated that, within the simulated time period of 40 years, forest management has a strong influence on the carbon budget. However, forest soils only react slightly to changes in the above-ground biomass. The results also showed that a storm frequency increase of 30% has a small impact on the national carbon budget of forests. To develop effective mitigation strategies for forest management, however, longer time periods must be regarded.
Trueman, R. J., Gonzalez-Meler, M. A. (2005). Accelerated belowground C cycling in a managed agriforest ecosystem exposed to elevated carbon dioxide concentrations. Global Change Biology 11 (8): 1258-1271
ABSTRACT: We investigated the effects of three elevated atmospheric CO2 levels on a Populus deltoides plantation at Biosphere 2 Laboratory in Oracle Arizona. Stable isotopes of carbon have been used as tracers to separate the carbon present before the CO2 treatments started (old C), from that fixed after CO2 treatments began (new C). Tree growth at elevated [CO2 ] increased inputs to soil organic matter (SOM) by increasing the production of fine roots and accelerating the rate of root C turnover. However, soil carbon content decreased as [CO2 ] in the atmosphere increased and inputs of new C were not found in SOM. Consequently, the rates of soil respiration increased by 141% and 176% in the 800 and 1200μL L−1 plantations, respectively, when compared with ambient [CO2 ] after 4 years of exposure. However, the increase in decomposition of old SOM (i.e. already present when CO2 treatments began) accounted for 72% and 69% of the increase in soil respiration seen under elevated [CO2 ]. This resulted in a net loss of soil C at a rate that was between 10 and 20 times faster at elevated [CO2 ] than at ambient conditions. The inability to retain new and old C in the soil may stem from the lack of stabilization of SOM, allowing for its rapid decomposition by soil heterotrophs.
Vetter, M., Wirth, C., Bottcher, H., Churkina, G., Schulze, E. D., Wutzler, T., Weber, G. (2005). Partitioning direct and indirect human-induced effects on carbon sequestration of managed coniferous forests using model simulations and forest inventories. Global Change Biology 11 (5): 810-827
ABSTRACT: Temperate forest ecosystems have recently been identified as an important net sink in the global carbon budget. The factors responsible for the strength of the sinks and their permanence, however, are less evident. In this paper, we quantify the present carbon sequestration in Thuringian managed coniferous forests. We quantify the effects of indirect human-induced environmental changes (increasing temperature, increasing atmospheric CO2 concentration and nitrogen fertilization), during the last century using BIOME-BGC, as well as the legacy effect of the current age-class distribution (forest inventories and BIOME-BGC). We focused on coniferous forests because these forests represent a large area of central European forests and detailed forest inventories were available.
The model indicates that environmental changes induced an increase in biomass C accumulation for all age classes during the last 20 years (1982–2001). Young and old stands had the highest changes in the biomass C accumulation during this period. During the last century mature stands (older than 80 years) turned from being almost carbon neutral to carbon sinks. In high elevations nitrogen deposition explained most of the increase of net ecosystem production (NEP) of forests. CO2 fertilization was the main factor increasing NEP of forests in the middle and low elevations.
According to the model, at present, total biomass C accumulation in coniferous forests of Thuringia was estimated at 1.51 t C ha−1 yr−1 with an averaged annual NEP of 1.42 t C ha−1 yr−1 and total net biome production of 1.03 t C ha−1 yr−1 (accounting for harvest). The annual averaged biomass carbon balance (BCB: biomass accumulation rate-harvest) was 1.12 t C ha−1 yr−1 (not including soil respiration), and was close to BCB from forest inventories (1.15 t C ha−1 yr−1 ). Indirect human impact resulted in 33% increase in modeled biomass carbon accumulation in coniferous forests in Thuringia during the last century. From the forest inventory data we estimated the legacy effect of the age-class distribution to account for 17% of the inventory-based sink. Isolating the environmental change effects showed that these effects can be large in a long-term, managed conifer forest.
E. A. H. Smithwick, M. E. Harmon, S. M. Remillard, S. A. Acker, J. F. Franklin (2002). Potential upper bounds of carbon stores in forests of the Pacific Northwest. Ecological Applications 12 (5): 1303-1317
ABSTRACT: Placing an upper bound to carbon (C) storage in forest ecosystems helps to constrain predictions on the amount of C that forest management strategies could sequester and the degree to which natural and anthropogenic disturbances change C storage. The potential, upper bound to C storage is difficult to approximate in the field because it requires studying old-growth forests, of which few remain. In this paper, we put an upper bound (or limit) on C storage in the Pacific Northwest (PNW) of the United States using field data from old-growth forests, which are near steady-state conditions. Specifically, the goals of this study were: (1) to approximate the upper bounds of C storage in the PNW by estimating total ecosystem carbon (TEC) stores of 43 old-growth forest stands in five distinct biogeoclimatic provinces and (2) to compare these TEC storage estimates with those from other biomes, globally. Finally, we suggest that the upper bounds of C storage in forests of the PNW are higher than current estimates of C stores, presumably due to a combination of natural and anthropogenic disturbances, which indicates a potentially substantial and economically significant role of C sequestration in the region. Results showed that coastal Oregon stands stored, on average, 1127 Mg C/ha, which was the highest for the study area, while stands in eastern Oregon stored the least, 195 Mg C/ha. In general, coastal Oregon stands stored 307 Mg C/ha more than coastal Washington stands. Similarly, the Oregon Cascades stands stored 75 Mg C/ha more, on average, than the Washington Cascades stands. A simple, area-weighted average TEC storage to 1 m soil depth (TEC100 ) for the PNW was 671 Mg C/ha. When soil was included only to 50 cm (TEC50 ), the area-weighted average was 640 Mg C/ha. Subtracting estimates of current forest C storage from the potential, upper bound of C storage in this study, a maximum of 338 Mg C/ha (TEC100 ) could be stored in PNW forests in addition to current stores.
ABSTRACT: The STANDCARB 2.0 model was used to examine the effects of partial harvest of trees within stands on forest-related carbon (C) stores in a typical Pacific NorthwestPseudotsuga /Tsuga forest. For harvest rotation intervals of 20 to 250 years the effect of completely dispersed (that is, a checkerboard) versus completely aggregated cutting patterns (that is, single blocks) was compared. The simulations indicated that forests with frequent, but partial removal of live trees can store as much C as those with complete tree harvest on less frequent intervals. Stores in forest products generally declined as the fraction of live trees harvested declined and as the interval between harvests increased. Although the proportion of total system stores in forest products increased as the frequency of harvests and proportion of trees removed increased, this did not offset the reduction in forest C stores these treatments caused. Spatial arrangement of harvest influenced tree species composition profoundly; however, the effects of aggregated versus dispersed cutting patterns on C stores were relatively small compared to the other treatments. This study indicates that there are multiple methods to increase C stores in the forest sector including either increasing the time between harvests or reducing the fraction of trees harvested during each harvest.
ABSTRACT: This paper reviews the effects of past forest management on carbon stocks in the United States, and the challenges for managing forest carbon resources in the 21st century. Forests in the United States were in approximate carbon balance with the atmosphere from 1600–1800. Utilization and land clearing caused a large pulse of forest carbon emissions during the 19th century, followed by regrowth and net forest carbon sequestration in the 20th century. Recent data and knowledge of the general behavior of forests after disturbance suggest that the rate of forest carbon sequestration is declining. A goal of an additional 100 to 200 Tg C/yr of forest carbon sequestration is achievable, but would require investment in inventory and monitoring, development of technology and practices, and assistance for land managers.
Muller, C., Eickhout, B., Zaehle, S., Bondeau, A., Cramer, W., Lucht, W. (2007). Effects of changes in CO2 , climate, and land use on the carbon balance of the land biosphere during the 21st century. Journal of Geophysical Research-Biogeosciences 112 (G2): 2032
ABSTRACT: We studied the effects of climate and land-use change on the global terrestrial carbon cycle for the 21st century. Using the process-based land biosphere model (LPJmL), we mechanistically simulated carbon dynamics for natural and managed lands (agriculture and forestry) and for land-use change processes. We ran LPJmL with twelve different dynamic land-use patterns and corresponding climate and atmospheric CO2 projections. These input data were supplied from the IMAGE 2.2 implementations of the IPCC-SRES storylines for the A2, B1, and B2 scenarios. Each of these SRES scenarios was implemented under four different assumptions on spatial climate patterns in IMAGE 2.2, resulting in twelve different Earth System projections. Our selection of SRES scenarios comprises deforestation and afforestation scenarios, bounding a broad range of possible land-use change. Projected land-use change under different socio-economic scenarios has profound effects on the terrestrial carbon balance: While climate change and CO2 fertilization cause an additional terrestrial carbon uptake of 105-225 PgC, land-use change causes terrestrial carbon losses of up to 445 PgC by 2100, dominating the terrestrial carbon balance under the A2 and B2 scenarios. Our results imply that the potential positive feedback of the terrestrial biosphere on anthropogenic climate change will be strongly affected by land-use change. Spatiotemporally explicit projections of land-use change and the effects of land management on terrestrial carbon dynamics need additional attention in future research.
R.E.J. Boerner, J. Huang, S. C. Hart (2008). Fire, thinning, and the carbon economy: Effects of fire and fire surrogate treatments on estimated carbon storage and sequestration rate. Forest Ecology and Management 255 (8-9): 3081-3097
ABSTRACT: Changes in estimated standing stocks of carbon (C) in vegetation, forest floor, dead wood, and mineral soil for the fire and fire surrogate (FFS) network sites were evaluated in relation to the application of prescribed fire, mechanical treatments designed as surrogates for prescribed fire, and the combination of mechanical treatment and fire. Pre-treatment C stocks and changes in C stocks over two intervals (pre-treatment to first post-treatment year and first post-treatment to a 2nd, 3rd, or 4th post-treatment year, depending on site) were evaluated using meta-analytical methods. Total C storage across the network averaged 185 ± 8 (standard error) Mg C ha−1 , of which 45% was in vegetation, 38% in soil organic matter, 10% in the forest floor and 7% in dead wood. C stored in vegetation was not significantly affected by prescribed fire, but decreased ~30 Mg ha−1 as the result of mechanical or mechanical + fire treatment; in contrast, forest floor C storage was reduced by ~1–7 Mg ha−1 by fire or mechanical + fire treatment, but unaffected by mechanical treatment alone. Neither dead wood C nor soil organic C was significantly affected by the treatments. At the network scale, total ecosystem C was not significantly affected by fire, though four individual sites did exhibit significant C losses to fire. Mechanical treatment, with or without fire, produced significant reductions of 16–32 Mg ha−1 during the first post-treatment year, but this was partially balanced by enhanced net C uptake of ~12 Mg ha−1 during the subsequent 1–3 years. In terms of C storage and uptake, western coniferous forests responded differently to the FFS treatments than did eastern deciduous, coniferous, and mixed forests, suggesting that optimal management for fire, harvesting, and C sequestration may differ between regions.
M. E. Harmon, B. Marks (2002). Effects of silvicultural practices on carbon stores in Douglas-fir – western hemlock forests in the Pacific Northwest, U.S.A.: results from a simulation model. Canadian Journal of Forest Research 32 (5): 863-877
ABSTRACT: We used a new model, STANDCARB, to examine effects of various treatments on carbon (C) pools in the Pacific Northwest forest sector. Simulation experiments, with five replicates of each treatment, were used to investigate the effects of initial conditions, tree establishment rates, rotation length, tree utilization level, and slash burning on ecosystem and forest products C stores. The forest examined was typical of the Cascades of Oregon and dominated by Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) and western hemlock (Tsuga heterophylla (Raf.) Sarg). Simulations were run until a C steady state was reached at the landscape level, and results were rescaled relative to the potential maximum C stored in a landscape. Simulation experiments indicated agricultural fields stored the least (15% of the maximum) and forests protected from fire stored the greatest amount (93% of the maximum) of landscape-level C. Conversion of old-growth forests to any other management or disturbance regime resulted in a net loss of C, whereas conversion of agricultural systems to forest systems had the opposite effect. The three factors, in order of increasing importance, most crucial in developing an optimum C storage system were (i) rotation length, (ii) amount of live mass harvested, and (iii) amount of detritus removed by slash burning. Carbon stores increased as rotation length increased but decreased as fraction of trees harvested and detritus removed increased. Simulations indicate partial harvest and minimal fire use may provide as many forest products as the traditional clearcut – broadcast-burn system while increasing C stores. Therefore, an adequate supply of wood products may not be incompatible with a system that increases C stores.
ABSTRACT: Management of forests for carbon uptake is an important tool in the effort to slow the increase in atmospheric CO2 and global warming. However, some current policies governing forest carbon credits actually promote avoidable CO2 release and punish actions that would increase long-term carbon storage. In fire-prone forests, management that reduces the risk of catastrophic carbon release resulting from stand-replacing wild-fire is considered to be a CO2 source, according to current accounting practices, even though such management may actually increase long-term carbon storage. Examining four of the largest wildfires in the US in 2002, we found that, for forest land that experienced catastrophic stand-replacing fire, prior thinning would have reduced CO2 release from live tree biomass by as much as 98%. Altering carbon accounting practices for forests that have historically experienced frequent, low-severity fire could provide an incentive for forest managers to reduce the risk of catastrophic fire and associated large carbon release events.
Mitchell, S.R., M.E. Harmon, K.E.B. O'Connell (2009). Forest fuel reduction alters fire severity and long-term carbon storage in three Pacific Northwest ecosystems. Ecological Applications 19 (3): 643-655
ABSTRACT: Two forest management objectives being debated in the context of federally managed landscapes in the U.S. Pacific Northwest involve a perceived trade-off between fire restoration and carbon sequestration. The former strategy would reduce fuel (and therefore C) that has accumulated through a century of fire suppression and exclusion which has led to extreme fire risk in some areas. The latter strategy would manage forests for enhanced C sequestration as a method of reducing atmospheric CO2 and associated threats from global climate change. We explored the trade-off between these two strategies by employing a forest ecosystem simulation model, STANDCARB, to examine the effects of fuel reduction on fire severity and the resulting long-term C dynamics among three Pacific Northwest ecosystems: the east Cascades ponderosa pine forests, the west Cascades western hemlock–Douglas-fir forests, and the Coast Range western hemlock–Sitka spruce forests. Our simulations indicate that fuel reduction treatments in these ecosystems consistently reduced fire severity. However, reducing the fraction by which C is lost in a wildfire requires the removal of a much greater amount of C, since most of the C stored in forest biomass (stem wood, branches, coarse woody debris) remains unconsumed even by high-severity wildfires. For this reason, all of the fuel reduction treatments simulated for the west Cascades and Coast Range ecosystems as well as most of the treatments simulated for the east Cascades resulted in a reduced mean stand C storage. One suggested method of compensating for such losses in C storage is to utilize C harvested in fuel reduction treatments as biofuels. Our analysis indicates that this will not be an effective strategy in the west Cascades and Coast Range over the next 100 years. We suggest that forest management plans aimed solely at ameliorating increases in atmospheric CO2 should forgo fuel reduction treatments in these ecosystems, with the possible exception of some east Cascades ponderosa pine stands with uncharacteristic levels of understory fuel accumulation. Balancing a demand for maximal landscape C storage with the demand for reduced wildfire severity will likely require treatments to be applied strategically throughout the landscape rather than indiscriminately treating all stands.
ABSTRACT: A 35-year controlled burning experiment in Minnesota oak savanna showed that fire frequency had a great impact on ecosystem carbon (C) stores. Specifically, compared to the historical fire regime, fire suppression led to an average of 1.8 Mg·ha−1 ·yr−1 of C storage, with most carbon stored in woody biomass. Forest floor carbon stores were also significantly impacted by fire frequency, but there were no detectable effects of fire suppression on carbon in soil and fine roots combined, or in woody debris. Total ecosystem C stores averaged 110 Mg/ha in stands experiencing presettlement fire frequencies, but 220 Mg/ha in stands experiencing fire suppression. If comparable rates of C storage were to occur in other ecosystems in response to the current extent of fire suppression in the United States, fire suppression in the USA might account for 8–20% of missing global carbon.
ABSTRACT: Forests are viewed as a potential sink for carbon (C) that might otherwise contribute to climate change. It is unclear, however, how to manage forests with frequent fire regimes to maximize C storage while reducing C emissions from prescribed burns or wildfire. We modeled the effects of eight different fuel treatments on tree-based C storage and release over a century, with and without wildfire. Model runs show that, after a century of growth without wildfire, the control stored the most C. However, when wildfire was included in the model, the control had the largest total C emission and largest reduction in live-tree-based C stocks. In model runs including wildfire, the final amount of tree-based C sequestered was most affected by the stand structure initially produced by the different fuel treatments. In wildfire-prone forests, tree-based C stocks were best protected by fuel treatments that produced a low-density stand structure dominated by large, fire-resistant pines.
ABSTRACT: Forests currently absorb billions of tons of CO2 globally every year, an economic subsidy worth hundreds of billions of dollars if an equivalent sink had to be created in other ways. Concerns about the permanency of forest carbon stocks, difficulties in quantifying stock changes, and the threat of environmental and socioeconomic impacts of large-scale reforestation programs have limited the uptake of forestry activities in climate policies. With political will and the involvement of tropical regions, forests can contribute to climate change protection through carbon sequestration as well as offering economic, environmental, and sociocultural benefits. A key opportunity in tropical regions is the reduction of carbon emissions from deforestation and degradation.
ABSTRACT: Adaptation in forestry is sustainable forest management that includes a climate change focus. Climate change over the next 100 years is expected to have significant impacts on forest ecosystems. The forestry community needs to evaluate the long-term effects of climate change on forests and determine what the community might do now and in the future to respond to this threat. Management can influence the timing and direction of forest adaptation at selected locations, but in many situations society will have to adjust to however forests adapt. Adapting to climate change in the face of the uncertain timing of impacts means we must have a suite of readily available options. A high priority will be coping with and adapting to forest disturbance while maintaining the genetic diversity and resilience of forest ecosystems. A framework for facilitating adaptation in forestry is discussed and a review of adaptive actions presented.
Depro, B.M., B.C. Murray, R.J. Alig, A. Shanks (2008). Public land, timber harvests, and climate mitigation: Quantifying carbon sequestration potential on U.S. public timberlands. Forest Ecology and Management 255 (3-4): 1122-1134
ABSTRACT: Scientists and policy makers have long recognized the role that forests can play in countering the atmospheric buildup of carbon dioxide (CO2 ), a greenhouse gas (GHG). In the United States, terrestrial carbon sequestration in private and public forests offsets approximately 11% of all GHG emissions from all sectors of the economy on an annual basis. Although much of the attention on forest carbon sequestration strategy in the United States has been on the role of private lands, public forests in the United States represent approximately 20% of the U.S. timberland area and also hold a significantly large share (30%) of the U.S. timber volume. With such a large standing timber inventory, these forested lands have considerable impact on the U.S. forest carbon balance. To help decision makers understand the carbon implications of potential changes in public timberland management, we compared a baseline timber harvest scenario with two alternative harvest scenarios and estimated annual carbon stock changes associated with each. Our analysis found that a “no timber harvest” scenario eliminating harvests on public lands would result in an annual increase of 17–29 million metric tonnes of carbon (MMTC) per year between 2010 and 2050—as much as a 43% increase over current sequestration levels on public timberlands and would offset up to 1.5% of total U.S. GHG emissions. In contrast, moving to a more intense harvesting policy similar to that which prevailed in the 1980s may result in annual carbon losses of 27–35 MMTC per year between 2010 and 2050. These losses would represent a significant decline (50–80%) in anticipated carbon sequestration associated with the existing timber harvest policies. If carbon sequestration were valued in the marketplace as part of a GHG offset program, the economic value of sequestered carbon on public lands could be substantial relative to timber harvest revenues.
ABSTRACT: This paper explores the tradeoff between resource extraction and net carbon sequestration in managing representative timber stands in the state of New Hampshire in the northeastern United States. In the absence of policies to promote forest carbon storage, land owners have incentives to employ clear-cut harvesting regimes with relatively short rotation periods. Under conservative assumptions regarding the social benefits of carbon storage, optimal rotation periods are extended by between 16 and 133 years depending on the forest type under consideration. If policy-makers pursued a cost-effective strategy to stabilize atmospheric carbon dioxide concentrations at twice the pre-industrial norm, optimal rotation periods would be extended by a full 180–347 years. The analysis suggests that partial harvesting regimes (in which approximately 35% of timber volume is removed at 15-year intervals after the timber stand reaches an initial age of 45 years) provide relatively high net benefits under a variety of circumstances. This finding is relevant because partial harvesting is an accepted and relatively common practice that could be adopted more widely.
E. Eriksson, A. R. Gillespie, L. Gustavsson, O. Langvall, M. Olsson, R. Sathre, J. Stendahl (2007). Integrated carbon analysis of forest management practices and wood substitution. Canadian Journal of Forest Research 37 (3): 671-681
ABSTRACT: The complex fluxes between standing and harvested carbon stocks, and the linkage between harvested biomass and fossil fuel substitution, call for a holistic, system-wide analysis in a life-cycle perspective to evaluate the impacts of forest management and forest product use on carbon balances. We have analysed the net carbon emission under alternative forest management strategies and product uses, considering the carbon fluxes and stocks associated with tree biomass, soils, and forest products. Simulations were made using three Norway spruce (Picea abies (L.) Karst.) forest management regimes (traditional, intensive management, and intensive fertilization), three slash management practices (no removal, removal, and removal with stumps), two forest product uses (construction material and biofuel), and two reference fossil fuels (coal and natural gas). The greatest reduction of net carbon emission occurred when the forest was fertilized, slash and stumps were harvested, wood was used as construction material, and the reference fossil fuel was coal. The lowest reduction occurred with a traditional forest management, forest residues retained on site, and harvested biomass was used as biofuel to replace natural gas. Product use had the greatest impact on net carbon emission, whereas forest management regime, reference fossil fuel, and forest residue usage as biofuel were less significant.
ABSTRACT: Only within the past 100 years have we, as recent immigrants to this continent, made a concerted effort to restore and manage the composition and productivity of North American forests. One of the earliest manifestations of management effects on growth, production, and sustainability was reforestation and land stabilization of wind- and water-eroded land wrought by abusive agriculture. In the past 50 years, basic and applied research has greatly increased forest productivity of desired species on many sites by integrating intensive forest management practices. Forest management was further enhanced by site-specific prescriptions made possible by finely honed soil and land classification systems interpreted specifically for forestry uses. Managers of our private and public forests are facing new challenges caused, in part, by public expectations that forests provide a myriad of services along with products; services that have been taken for granted and are poorly monetized. Managing forests simultaneously for wood, biodiversity, carbon sequestration, energy, water quality, flood control, habitat, and recreation is the 21st century challenge for foresters who need science to underpin their prescriptions. This paper is a review of forest management effects on growth, production, and sustainability of forest ecosystems.
Johnson, C. E.,, Johnson, A. H.,, Huntington, T. G., Siccama, T. G. (1991). Whole-tree clear-cutting effects on soil horizons and organic matter pools. Soil Science Society American Journal 55: 497-502
ABSTRACT: Timber harvest results in physical disturbance and relocation of soil materials. This study was undertaken to assess the degree to which logging altered soil horizonation, bulk density, and organic-matter pools at a northern hardwood forest site underlain by Spodosols. Soils were sampled immediately before and 3 yr after the commercial whole-tree harvest of Watershed 5 at the Hubbard Brook Exerpimental Forest in central New Hampshire. The activity of logging machinery resulted in redistribution of organic matter within the solum. Thus, the thickness of the O horizon decreased from 6.9 cm to 5.5 cm, while O horizon mass and organic-matter content increased (from 8.7–12.2 kg m–2 and from 5.4–5.7 kg m–2 , respectively). One-fourth of the postharvest soil pits exhibited an Ap horizon, which was not present prior to harvesting and was formed from soil of the O, E, and Bh horizons. Compaction of the soil during the logging operation resulted in increased (5–15%) bulk density in the upper 20 cm of mineral soil. The total pool of organic matter in the solum did not change following harvesting. Thus, losses of organic matter via streamwater and respiration were approximately balanced by inputs from decaying roots and leaf litter. The conservation of organic matter following harvesting is important in preserving soil fertility, since labile nutrients in northeastern Spodosols are generally associated with organic matter.
ABSTRACT: The literature on soil C change with forest harvesting, cultivation, site preparation, burning, fertilization, N fixation, and species change is reviewed. No general trend toward lower soil C with forest harvesting was apparent, unless harvesting is followed by intense burning or cultivation. Most studies show no significant change (± 10%) with harvesting only, a few studies show large net losses, and a few studies show a net gain following harvesting. Cultivation, on the other hand, results in a large (up to 50%) loss in soil C in most (but not all) cases. Low-intensity rescribed fire usually results in little change in soil C, but intense presribed fire or wildfire can result in a large loss of soil C. Species change can have either no effect or large effects on soil C, depending primarily upon rooting patterns. Fertilization and (especially) nitrogen fixation cause increases in soil C in the majority of cases, and represent an opportunity for sequestering soil C and causing long-term improvements in site fertility.
Makundi, W.R. (1997). Global climate change mitigation and sustainable forest management — the challenge of monitoring and verification. Mitigation and Adaptation Strategies for Global Change 2: 133-155
ABSTRACT: In this paper, sustainable forest management is discussed within the historical and theoretical framework of the sustainable development debate. The various criteria and indicators for sustainable forest management put forth by different institutions are critically explored. Specific types of climate change mitigation policies/projects in the forest sector are identified and examined in the light of the general criteria for sustainable forest management. Areas of compatibility and contradiction between the climate mitigation objectives and the minimum criteria for sustainable forest management are identified and discussed. Emphasis is put on the problems of monitoring and verifying carbon benefits associated with such projects given their impacts on pre-existing policy objectives on sustainable forest management. The implications of such policy interactions on assignment of carbon credits from forest projects under Joint Implementation/Activities Implemented Jointly initiatives are discussed. The paper concludes that a comprehensive monitoring and verification regime must include an impact assessment on the criteria covered under other agreements such as the Biodiversity and/or Desertification Conventions. The actual carbon credit assigned to a specific project should at least take into account the negative impacts on the criteria for sustainable forest management. The value of the impacts and/or the procedure to evaluate them need to be established by interested parties such as the Councils of the respective Conventions.
ABSTRACT: We offer a conceptual framework for managing forested ecosystems under an assumption that future environments will be different from present but that we cannot be certain about the specifics of change. We encourage flexible approaches that promote reversible and incremental steps, and that favor ongoing learning and capacity to modify direction as situations change. We suggest that no single solution fits all future challenges, especially in the context of changing climates, and that the best strategy is to mix different approaches for different situations. Resources managers will be challenged to integrate adaptation strategies (actions that help ecosystems accommodate changes adaptively) and mitigation strategies (actions that enable ecosystems to reduce anthropogenic influences on global climate) into overall plans. Adaptive strategies include resistance options (forestall impacts and protect highly valued resources), resilience options (improve the capacity of ecosystems to return to desired conditions after disturbance), and response options (facilitate transition of ecosystems from current to new conditions). Mitigation strategies include options to sequester carbon and reduce overall greenhouse gas emissions. Priority-setting approaches (e.g., triage), appropriate for rapidly changing conditions and for situations where needs are greater than available capacity to respond, will become increasingly important in the future.
ABSTRACT: General warming in the Northern Hemisphere has been recorded since the end of the 1800s following the Little Ice Age. Records of glacier retreat during the last 100 years over the entire globe independently confirmed the recorded trend in global temperature rise. Several studies have illustrated various responses to this climate forcing, i.e., the recorded changes in temperature and precipitation concurrent with the increase in atmospheric CO2 concentration, increases in density of tree populations, declines in tree populations, treeline displacement or lack thereof, lengthening of the growing season, and enhanced tree growth. It is critical that we identify the tools needed to estimate potential consequences of climate change on forest ecosystems and develop management practices and policies adapted to projected drifts in the geographic distribution of ecosystems.
FIRST PARAGRAPH: When and if the United States decides on mandatory policies to address global climate change, it will be necessary to decide whether carbon sequestration should be part of the domestic portfolio of compliance activities. The potential costs of carbon sequestration policies will presumably be a major criterion, so it is important to assess the cost of supplying forest-based carbon sequestration in the United States. In this report we survey major studies, examine the factors that have affected their carbon sequestration cost estimates, and synthesize the results.
ABSTRACT: The carbon sequestered by restoring forests is greater than the emissions avoided by the use of the liquid biofuels.
Keith, H., Mackey, B. G., Lindenmayer, D. B. (2009). Re-evaluation of forest biomass carbon stocks and lessons from the world's most carbon-dense forests. Proceedings of the National Academy of Sciences 106 (28): 11635-11640
ABSTRACT: From analysis of published global site biomass data (n = 136) from primary forests, we discovered (i) the world's highest known total biomass carbon density (living plus dead) of 1,867 tonnes carbon per ha (average value from 13 sites) occurs in Australian temperate moistEucalyptus regnans forests, and (ii) average values of the global site biomass data were higher for sampled temperate moist forests (n = 44) than for sampled tropical (n = 36) and boreal (n = 52) forests (n is number of sites per forest biome). Spatially averaged Intergovernmental Panel on Climate Change biome default values are lower than our average site values for temperate moist forests, because the temperate biome contains a diversity of forest ecosystem types that support a range of mature carbon stocks or have a long land-use history with reduced carbon stocks. We describe a framework for identifying forests important for carbon storage based on the factors that account for high biomass carbon densities, including (i) relatively cool temperatures and moderately high precipitation producing rates of fast growth but slow decomposition, and (ii) older forests that are often multiaged and multilayered and have experienced minimal human disturbance. Our results are relevant to negotiations under the United Nations Framework Convention on Climate Change regarding forest conservation, management, and restoration. Conserving forests with large stocks of biomass from deforestation and degradation avoids significant carbon emissions to the atmosphere, irrespective of the source country, and should be among allowable mitigation activities. Similarly, management that allows restoration of a forest's carbon sequestration potential also should be recognized.