Criterion 2: MAINTAINING THE PRODUCTIVE CAPACITY OF FOREST ECOSYSTEMS

I. INTRODUCTION

The area of forest land in the United States is less than it was prior to European settlement, but the downward trend stopped in the 1920's and the area of forest land on a national level has increased slightly, mostly in the East. Moreover, average stocking rates, intensity of management, and the total area under management have continually increased, and the average area of tree stands is increasing. The result is an increasing production of wood fiber on the forest lands of the U.S.

Plantations have been a part of forest management since the early 1900's. Timber plantations were established through the Civilian Conservation Corps (CCC) in the 1930's; the Soil Bank Program in the 1950's; several other tree planting incentive programs at the federal, state, and local level; and through investments by private landowners and forest industries. As plantations mature and are harvested, some are replanted for another rotation of trees, some revert back to natural stands, and some are converted to other land uses. The relative percentage of plantation to natural stands, or amount of forest area converted to other uses varies by region, but data on the specific nature of changes in forest lands is lacking.

ii. INDICATOR REPORTS

INDICATOR 10: Area of forest land and net area of forest land available for timber production.

In many countries, the traditional calculation of timber production potential has been based on total forest. However, in the U.S. this measure is less effective because spiritual, recreational, scientific, or educational values may be given priority over commodity production.

Data Summary

Information sources for productive capacity of forest ecosystems are generally the same as for biodiversity. Again, information is generally available for timberlands, but is limited for other forest lands.

In 1992, about two-thirds of the total area of forest land in the U.S. was available for timber production. Twenty-seven percent of forest land was unproductive and 6.5 percent was in protected reserves. In the Eastern U.S., 94 percent of the total forest area was timberland, but only 37 percent was timberland in the western States. In the eastern States, the regional percentages of timberland to total forested acreage ranged from 83 percent in the Great Plains Region to 96 percent in the Southeast Region. The South Central Region had the most area of timberland - 46 million hectares (Table 3-1).

Almost 50 percent of the 52 million hectares of timberland in the West was located in the Intermountain Region, and almost 30 percent in the Pacific Northwest Region. The Pacific Southwest and Alaska Regions accounted for the remaining 20 percent of the total area of western timberland. All tracts of timberland in the West are being evaluated to determine their primary long-term uses. These evaluations may result in reclassification of western timberlands in the future.

Interpretation

Timberlands are increasing both in area and volume. Most timberlands in the East are on productive sites, and in the West they tend to be on sites with lower average annual productivity. However, some sites in the West, and especially in the Pacific Northwest, have the greatest average annual productivity of any forested land in the nation. As pressure continues for increased production of wood fiber, management will focus on highly productive sites for intense cultivation. By increasing stocking on the most productive sites, wood production could be increased without added demand on the less productive sites. Many forests, especially in the East, are now dominated by early successional stages, which tend to have fast growing species. As these are replaced by later stages, productivity may decline.

Data for the area of timberland available for production are contained in standard reports produced by FIA and other analyses are available on a sub-regional scale throughout the country. Trend information is available for all RPA assessment dates as well as regions, States, groups of counties, and non-traditional boundaries using the RPA database, the Eastside database, the Westside database, and auxiliary databases. Supplementary data on slope, volume, timber quality, and other variables that describe availability for production can be extracted from the Eastside and Westside databases and auxiliary databases maintained by regional FIA projects. Comprehensive data are not available for other forest lands at the present time.

INDICATOR 11: Total growing stock of both merchantable and nonmerchantable tree species on forest land available for timber production

Measurement of merchantable and non-merchantable growing stock provides an indication of timber supply opportunities.

Data Summary

As the nation's timberlands have matured, the percentage of the total volume represented in sawtimber-stand size class has correspondingly increased. The net volume of growing stock on timberland in 1992 totaled 22.2 billion cubic meters, 5 percent more than in 1977. In the Eastern U.S., between 1977 and 1992 the net volume of growing stock increased from 10.6 billion cubic meters to more than 13.0 billion cubic meters. While the volume of all major species in the East increased over the 15 years, a 31 percent increase in hardwood net volume was the greatest. Softwood net volume grew by only 10 percent over the same period.

In the Western U.S., net volume of growing stock on timberland decreased slightly between 1977 and 1992. Most major conifer species groups decreased, while hardwoods increased. The largest change in the West occurred in the western hemlock species group, which declined from about 1.5 billion cubic meters in 1977 to 0.9 billion cubic meters in 1992. In 1977, about 10 percent of the total volume was in rough, rotten, and sound dead trees, by 1992, that percentage had dropped to just 8 percent of the total volume.

Net volume of growing stock on timber land in the United States is shown for 1977, 1987, and 1992 in Tables 3-3, 3-4, and 3-5, respectively. Data are compiled from inventories conducted by the US Forest Service, Forest Inventory and Analysis (FIA) Program. Data for tree species considered "noncommercial" are typically included in retrievals for "live-tree volume" and are available from the Eastside and Westside databases and auxiliary databases maintained by regional FIA Programs. Some information for noncommercial species is available from the regional FIA Programs, but has not been compiled for National figures. Additional trend data for subregions such as States and groups of counties are available from most regional FIA Programs. Projections of expected future inventories of growing stock through the year 2040 are contained in the 1993 RPA Timber Assessment Update.

 

INDICATOR 12: The area and growing stock of plantations of native and exotic species.

Forest plantations provide a measure of forest management intensity, or of efforts to reclaim degraded lands or marginal agricultural lands. They may also indicate the creation of ecologically simplified forest types (if management does not take into account biological diversity).

Data Summary

Nationally, growing stock volume in plantations was estimated to be almost 700 million cubic meters in 1992 (Table 3-5). Plantations averaged 48 cubic meters of growing stock volume per hectare in 1992. Generally, growing stock volume per hectare is increasing as the average age of plantations is increasing. Records maintained since 1950 indicate a relatively steady increase in the area of timberland annually planted or direct seeded. In the 1950's, an estimated 198 thousand hectares of forest land were established by artificial means, compared to an estimated 850 thousand hectares established in the 1960's, 839 thousand hectares in the 1970's, and 1.19 million hectares inn the 1980's.

In the Great Plains, nearly all tree planting efforts have been for purposes other than timber production and, therefore, are generally not represented in plantation area or volume data. Most plantations in that region are established as windbreaks, wildlife habitat, etc., producing significant volumes that may eventually be used for firewood, lumber, posts, etc. Tree planting in the West is primarily used as a tool to re-establish timberlands, typically as a supplement to natural regeneration after harvest, rather than as a tool to increase the timberland area. In 1992, less than 5 percent of the total area classified as plantation in the U.S. was in the West.

In 1992, 86 percent of the total area of timberland classified as plantation was located in the South, primarily as conifer (loblolly pine) plantations. The Conservation Reserve Program (CRP) has helped convert thousands of hectares from agricultural to timberland uses. In the South, conversion of natural stands to plantations has proceeded to the point where 45 percent of the current total pine forest originated from planting or seeding. Plantation management has reduced the area of longleaf forests from more than 24.3 million hectares in the 1950's to 1.3 million hectares by 1993. In 1970, the South had 76.7 million hectares of timberland, of which 4.9 million hectares were in pine plantation. This represented 6 percent of the total area of timberland. By 1985, 11 percent of all timberlands were in pine plantation (8.5 million hectares of pine plantations, out of 73.7 million hectares, total). While the total area of timberland was decreasing between 1970 and 1985, the total area of plantations was increasing. In the Mid-South (a subset of the South), the area of timberland in pine plantations has increased from about 330 thousand hectares in 1952 to more than 3.6 million hectares in 1985. By 1985, planted pine accounted for 9 percent of all Mid-South timberland.

In the Lake States, although the total area of timberland has increased in recent years, the area of timberland in plantations has decreased. Tree plantations in that region primarily contain conifer species. In 1992, less than 2 percent of the total plantation area was located in the Northeast.

The area in plantation will continue to increase in the South and probably remain constant in other regions.

Interpretation

Because trees less than 12.7 cm are not included in volume calculations, the total volume on plantations is difficult to determine. Survival rates within plantations are not available in the data, therefore overall stocking can vary from over-stocked to poorly stocked. This has an important influence on volume calculations. The degree of natural regeneration in plantations, especially in the West, is not considered, and may result in a weakening of data for the West. Species composition, whether involving exotic or native species, is not feasible for the entire nation but can be determined for the South.

INDICATOR 13: Annual removal of wood products compared to the volume determined to be sustainable.

By monitoring the volume of wood and non-wood forest products removed annually, relative to the amount that could be removed sustainably, managers can consider a forest=s availability to provide a continuing supply of forest products and economic and forest management opportunities. Useful indices can be derived by expressing the three components of inventory change (net growth, removals, and mortality) as proportions of inventory volume and by tracking these indices over time.

Forest Inventory and Analysis (FIA) projects have reported comparable data for 1976, 1986, and 1991, and these data are included in RPA documents. To date, inventory data are available for all timberland in the U.S. The agency is conducting an inventory of reserved forest land. It will take at least a full cycle to complete the inventory of reserved land.

Information on inventory, net growth, removals, and mortality is available on a State-by-State basis from regional FIA projects. In most cases, the data are available for a wide range of additional classification variables, such as ownership, stand size class, stocking class, etc.

Data Summary

Although net growth still exceeds removal by a considerable margin, the growth-to-removal ratio has decreased over the three dates reported, primarily due to expansion of removals and moderation of net growth (Table 3-6). One factor in the moderation of net growth has been the harvest of older softwood stands with high levels of accretion, which have been replaced with vigorous young stands that do not contribute to net growth until the trees grow to merchantable size (12.7 centimeters). Total exploitable growing stock volume steadily increased during the 1950's, but has leveled-off since the 1970's. In 1992 there were an estimated 22 billion cubic meters of growing stock on U.S. timberlands. Between 1950 and 1977, exploitable softwood growing stock volume grew, and then slightly decreased to a level of almost 12.6 billion cubic meters in 1992. On the other hand, exploitable hardwood growing stock volume has consistently increased during all inventory periods, and was reported to be more than 9.4 billion cubic meters in 1992.

In 1950, 414 million cubic meters of growing stock volume were removed from the America=s timberlands. Total gross growth in 1950 was estimated to be 499 million cubic meters, with a net change in growing stock volume of an additional 85 million cubic meters; compared to

218 million cubic meters in 1977 and more than 149 million cubic meters in 1992.

The trend toward chip mills for fiberboard and oriented strand board has implications for removals from forest land. Since the early 1980's chip mills have increased significantly. There are concerns about the effect on long-term sustainability of the total removal of wood fiber in harvesting operations associated with this industry. Analysis of this aspect of timber removals has not yet been done, but should be considered in future efforts.

The growth-to-removal ratio decreased from 1.54 in 1976 to 1.33 in 1991, primarily due to increased removal rates and relatively constant growth.. Growth-to-removal ratios were larger for hardwoods than for softwoods in both time periods (Table 3-7).

 

Change factors include gross growth, mortality (gross growth minus mortality equals net growth), and removals. Gross growth averaged 2.9 percent of total growing stock volume in 1952, compared to 3.5 percent in 1991. Mortality averaged 0.6 percent of total growing stock volume in 1952 (0.7 percent in 1991), resulting in an average annual net growth, as a percent of total volume, of 2.3 percent (2.8 percent in 1991). The rate of net annual growth as a percent of total volume was larger for hardwoods than for softwoods, but both were consistently above 2 percent for almost all time periods.

In 1991, 2.4 percent of the total softwood growing stock volume was removed, compared to 1.6 percent of the total hardwood growing stock volume removed. Annual net change (net growth minus removals) as a percent of total growing stock volume, was 1.1 percent greater in 1976 (data for annual removals are not available in this format prior to 1976) and 10.7 percent greater in 1991.

Interpretation

Despite the decrease in the growth-to-removal ratio, the ratio is 1.0 or greater, representing a situation where growth matches or more than matches removal. Findings for net change suggest that additions to total growing stock volume have decreased, although removals could be increased by almost a third (an additional 150 million cubic meters annually) and yet not be above total annual net growth.

Because managers lack information for all forest lands, the total volume cannot be determined. Data related to timberlands could be expanded to include all forest lands, application of those projections would be limited.

INDICATOR 14: Annual removal of nontimber forest products (e.g., fur-bearing animals, berries, mushrooms, game), compared to the level determined to be sustainable.

Monitoring the annual volume of wood and non-wood forest products removed, relative to the amount that could be removed on a sustainable basis, provides an indication of a forest's ability to provide a continuing supply of forest products, and economic and forest management opportunities. This indicator might also be used to reflect the values that society gives to forest resources by measuring the care that is given to their management. Non-timber forest products include game and fur-bearing animals, nuts and seeds, berries, mushrooms, oils, foliage, medicinal plants, peat and fuelwood, forage, etc. Water regulation, biodiversity conservation, recreational or spiritual values, and carbon release offsets are assessed under separate indicators.

Many non-timber forest products are subject to limited regulation or are not regulated at all, either because their use is highly localized, or their harvest rates do not appear to immediately threaten the sustainability of the resource. Many non-timber products have considerable importance to Native American Tribal members, and are specifically identified in treaty rights. However, because their economic importance or the potential impacts of their harvest are often not recognized in the larger society, individual subsistence or recreational harvesting of products are less often regulated via permits. Activities such as hunting, fur-trapping, and commercial seed or berry collecting are often not regulated.

Trends are very difficult to determine where there are no data to support analyses. In general, the majority of non-timber products depend on the integrity of habitat, and harvesting apparently does not destroy the habitat. For example, berry production is dependent upon a habitat that supports the plant that produces the berries. Berry collection in any given year does not directly affect the sustainability of berries, since only the fruiting bodies are being harvested, not the plants themselves. This holds true for all non-timber products, such as mushrooms, nuts and seeds, and berries, moss and lichens, pine straw, etc. The production of many non-timber forest products depends on keeping the forest base in place and utilizing the benefits while not impacting the overall health of the ecosystem. If the ecosystem can be managed on a sustainable basis, then non-timber benefits= production can be considered sustainable.

In cases where harvest of the non-timber product involves removing plants, such as with oils, fuelwood, foliage, medicinal plants, etc., if the habitat is maintained, then replacement with additional plants can be encouraged through active management techniques, and the sustainability of that resource can be attained.

Considerable data are available on the status of game animals, although the quality and quantity of such data varies from State to State. From a sustainability viewpoint, one can assume that of all of the non-timber products, game animal production is the most likely to be considered sustainable, due to the high level of management given to maintaining viable populations.

Interpretation

Definitive conclusions cannot be determined at this time, since no "hard" data are available on a national scale. However, with the advent of ecosystem management, which seeks to integrate biological, ecological, geophysical, and silvicultural information to develop adaptive management practices that conserve biological diversity and maintain ecological functions, the potential sustainability of non-timber products should be enhanced.

In North America, most non-timber products removed from forest ecosystems are highly localized, and productivity may vary greatly from site to site. For that reason, meaningful data on their production and sustainability nationwide are difficult to gather. For example, the production and harvest potential of mushrooms varies from one region to another, from one ecosystem to another, and from one cultural/social group to another.

The sustainability of a product that is based on the presence of habitat, as well as natural population cycles, must be determined on a long-term, temporal scale. The manager must take into account many years= harvest or production records to make any meaningful determinations or long-term management decisions.

The periodicity and movement capabilities of a forest resource often make it difficult to inventory or monitor a forest product. Many non-timber products may be inventoried during their fruiting season. If data collection is made when the fruit are not available, the results will be problematic. Because many wildlife species move from one micro-habitat area to another, the repeatability of any monitoring effort must take into consideration the fact that even though the species might not be detected, it may use the habitat that is being investigated. As a result of these and other concerns, inventory and monitoring efforts intended to assemble data for future analyses must focus on specific products and the time/spatial frames necessary to adequately measure that specific product.

In theory, the sustainability of game and fur-bearing animals depends on the balance of annual mortality (harvest plus natural mortality) and reproduction. In reality, populations are in flux because of unanticipated events such as adverse weather or disease. Therefore, the setting of seasons and bag limits is both an art and a science.

Gathering berries, mushrooms, and other specialty products is increasing in popularity. The role of these products in ecosystem functions and processes is not well understood by most resource managers. The increased economic activity brought by the wild mushroom markets has stimulated interest in research on the role of mushrooms in ecosystems but, to date, there has been no agreement on the level of gathering that might be sustainable. There are harvest data for game and fur-bearing animals that are maintained by public agencies in each State, and some data are kept on populations. The quality of data varies from State to State and aside from what has been presented in a few localized studies, there is little information on management of specialty products.

On a local scale, thousands of non-timber products= studies have been conducted. An in-depth literature review might result in a meaningful collection of such information, and allow researchers to begin to correlate relevant data from a variety of studies. In turn, this could facilitate an analysis of the sustainability of non-timber products on a regional scale. It would also be valuable to access the traditional forest related knowledge about these products held by Indian tribes to assist researchers in this analysis. Unfortunately, the time necessary to complete this task is not available for this First Approximation Report.

Traditionally, harvest regulations for game and fur-bearing animals are devised and implemented to ensure sustainability. Species managed under State jurisdiction include big game, small game, fur-bearing animals, and recreational fisheries. How regulations are promulgated varies from State to State. Species under Federal jurisdiction include migratory birds and commercial fisheries. The U.S. is a signatory to the Migratory Bird Treaty Act of 1918. Hunting of migratory birds is prohibited unless specifically permitted by the Secretary of the Interior.

Harvest data for game and fur-bearers are maintained by agencies in each State, as are some data on populations. The quality of the data varies by State. Aside from localized studies, there is little information on the management of specialty products.

iii. SUMMARY FOR THE CRITERION

The maintenance of the productive capacity of forest ecosystems in the U.S. has been measured by five indicators of land availability for timber production, merchantable and nonmerchantable growing stock available for timber production, area and growing stock of plantations, and the sustainable removals of wood and non-wood products. The following highlights reflect the significant trends and indications of this criterion in relation to the sustainability of U.S. forests.

Highlights

Timberlands in the United States are increasing in area and volume. Most timberlands in the East are on productive sites and, in the West, they tend to be on sites with lower average annual productivity. However, some sites in the West have the greatest average annual productivities of any forest land in the Nation, especially in the Pacific Northwest.

Pressure is expected to continue for increased production of wood fiber. On many of the most productive sites, stocking levels can be enhanced which will enable greater volumes of wood to be produced and lessen the harvesting pressure on site with lower productivity potentials.

There is a concern that timber volume will decline over time because of forest succession, especially in the East where many of the earlier successional forest types typically have large volumes with high growth rates.

In the Eastern US, all major species groups increased in their net volume of growing stock on timberland between 1977 and 1992. In the Western U.S., total growing stock net volume on timberland decreased slightly between 1977 and 1992.

Records since 1950 indicate that the area of timberland annually planted or direct seeded in the US steadily grew during the 1950's, declined in the 1960's, and has steadily increased since the 1970's. The area of plantations will continue to increase in the South and probably remain constant in other regions of the U.S.

The growth to removal ratio of wood products has decreased in recent decades. Softwood exploitable growing stock volume for the nation grew from 1950 through 1977 and then slightly decreased slightly from 1977 to 1992. Hardwood exploitable growing stock volume has consistently increased between all inventory periods. Growth to removal ratios were larger for hardwoods than for softwoods in both time periods.

In general, the majority of the non-timber products depend on habitat for their production. The sustainability of many non-timber forest products depends on keeping the forest base in place and utilizing the benefits while not impacting the overall health of the ecosystem.

With the advent of ecosystem management which integrates biological, ecological, geophysical, and silvicultural information, as well as socio-economic information, to develop adaptive management practices that conserve biological diversity and maintain ecological functions, the potential sustainability of non-timber products should be enhanced.

Gaps

Detailed inventories and assessments are not available to determine productivity for forest lands that are not classified as timberlands. Also, while productivity of timberlands is reasonably well documented, the availability of that timberland for harvest cannot be known with certainty in most cases.

Total volume on plantations is difficult to determine because trees less than 12.7 cm are not included in volume calculations. Survival rates for plantations are also not included in the data and thus overall stocking can vary from over-stocked to poorly stocked; this has an important influence on volume calculations. The degree of natural regeneration in plantings, especially in the West is not considered, resulting in a weakening of the data for the West.

Total volume can not be determined because of a lack of information for all forest lands. Data related to timberlands could be expanded to all forest lands but projections would be limited in application.

The majority of the non-timber products from forest ecosystems in the U.S. are localized. Data related to their production and sustainability are very difficult to gather on a national basis due to the localized nature of their habitat and ensuing production. For example, the production and potential harvest of mushrooms varies from one region to another, from one ecosystem to another, and from one cultural/social group to another.

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