|Photo courtesy of Joseph O'Brien, USDA Forest Service, Bugwood.org.|
Red pine is described as a dominant species in the following vegetation classifications and locations.Michigan:
Red pine communities on sand dunes at the southern end of Lake Michigan 
Red pine communities on the Vanderbilt moraines in the lower part of the state
Red pine communities on sand dunes on the west coast of Lake Michigan
Eastern white pine-red pine communities on steep end-moraine ridges of Williamsburg
Eastern white pine-red pine forests on Presque Isle at the extreme northern end of the lower part of the state
Red pine communities in upland forests near Cheboygan
Eastern white pine-red pine forests at the Grand Marais Sandy End moraine and outwash area of Lake Superior
Eastern white pine-red pine forests on the Spread Eagle-Dunbar Barrens
Eastern white pine-red pine-northern red oak (Quercus rubra) forests on the Michigamme Highland
Eastern white pine-red pine forests on the Lac Veaux Desert outwash plain
Eastern white pine-red pine forests in the Gogebic-Penokee Iron Range
Eastern white pine-red pine-northern red oak on bedrock ridges with thin soil at Calumet 
Eastern white pine-red pine-quaking aspen (Populus tremuloides) forest at Isle Royale National Park 
Red pine communities on upland sites of the Boundary Waters Canoe Area 
Red pine communities near the shores of the Boundary Waters Canoe Area 
Eastern white pine-red pine forests on the Mille Lac uplands along Mille Lac Lake
Eastern white pine-red pine forests on Itasca, Alexandria, and St Croix moraines
Eastern white pine-red pine forests on the Black Duck till plains
Eastern white pine-red pine forests on the St Louis moraines
Eastern white pine-red pine forests on the North Shore Highlands of Lake Superior
Eastern white pine-red pine forests along the Border Lakes
Eastern white pine-red pine forests on the Littlefork-Vermilion uplands 
Red pine-eastern white pine/twinflower (Linnaea borealis) habitat type on dry hilltops and upper slopes of Voyageurs National Park 
Red pine-jack pine upland forests on sand or loamy sand soils in Itasca State Park 
Red pine-eastern white pine-paper birch-maple (Betula papyrifera-Acer spp.) subclimax association at low elevations on shallow sandy soil of the White Mountain National Forest
Northern red oak-eastern white pine-red pine-red maple (A. rubrum) subclimax association on long, steep southerly-facing slopes at low to middle elevation in the White Mountain National Forest
Red pine-eastern white pine-red maple forest association on deep sandy or cobble outwash soils in the White Mountain National Forest 
Eastern white pine-red pine-jack pine ecosystem on smooth to irregular plains and tablelands 
Red pine-eastern white pine on sand bars of the lee shores of the Apostle Islands 
Red pine-eastern white pine-jack pine communities on outwash soils of southern Washburn County 
Eastern white pine-red pine communities on the Spread Eagle-Dunbar Barrens
Eastern white pine-red pine forests on the Lac Veaux Desert outwash plain
Eastern white pine-red pine forests in the Gogebic-Penokee Iron Range
Eastern white pine-red pine forests on the Mille Lac uplands along Mille Lac Lake 
Red pine monotypic communities on sand barrens of the Ottawa Valley 
Red pine monotypic or mixed red pine-eastern white pine-jack pine communities, typically on level or rolling sand plains 
Red pine upland forests in Algonquin Park 
Red pine monotypic or mixed red pine-eastern white pine-jack pine communities, typically on level or rolling sand plains in the Lake States 
Red pine-eastern white pine forests in mesic areas and grading into the ice-contact hills of the northern Great Lakes 
Red pine communities in the Great Lakes Canadian forests 
|Male red pine cones. Photo courtesy of Joseph
O'Brien, USDA Forest Service, Bugwood.org.
|Female red pine cones. Photo courtesy of USDA Forest Service-Rocky Mountain Region Archive, Bugwood.org.|
GENERAL BOTANICAL CHARACTERISTICS:
This description provides characteristics that may be relevant to fire ecology, and is not meant for identification. Keys for identification are available (e.g., [52,80,89,96,267]).
Aboveground description: Red pine is a long-lived (200-400 years), coniferous tree [22,57,89,231,252]. It grows in pure, even-aged stands and uneven-aged mixed stands primarily with eastern white pine, jack pine, and/or quaking aspen [252,258]. Red pine has an average height of 75 feet (23 m), but under ideal conditions may grow as tall as 200 feet (50 m) [96,107,252,266,267]. It has a straight trunk with little taper, few branches occurring below the canopy [231,252], and an average DBH of 10 to 20 inches (30-60 cm) [96,231,252,267], with a maximum reported DBH of 59.8 inches (152 cm) . The bark is furrowed and cross-checked into irregular rectangular, scaly plates up to 2 inches (6 cm) thick [96,266]. Details on the thermophysical properties of red pine bark are available in Reifsnyder and others .
Red pine has 2 straight to slightly twisted, flexible, slender, sharp-pointed needles/fascicle, measuring 4 to 6.7 inches (9-17 cm) long [80,89,96,107,252,267]. The majority of red pine needles live for 3 years, but some may persist for as long as 6 years [80,87,107,252,266]. Red pine cones are produced near the tips of twigs  and are approximately 1.4 to 3 inches (3.5-7 cm) long [80,89,96]. The middle third of the crown produces the greatest number and heaviest cones [71,231]. The cones contain ovoid seeds 3 to 5 mm across [96,107]. On Black Island in Lake Winnipeg, Manitoba, red pine cones averaged 1.91 × 1.08 inches (48.61 × 27.47 mm) long, with a mean fresh mass of about 0.49 ounce (13.88 g). The mean number of seeds/cone was 53 .
Crown structure: Red pine has a dense and symmetrical, generally ovoid-shaped crown and upcurved branches with stout twigs up to 0.4 inch (1 cm) thick [89,96,252]. One whorl of branches is produced annually from lateral buds formed at the leading shoot. Occasionally a second flush produces shoots in late summer, likely due to substantial rainfall after a dry period. Foliage weight increases from the top downwards for the first few whorls, remains constant for several more, and then diminishes towards the crown base, with the mean weight at or slightly below the midpoint. Crowns are enlarged by the annual extension of the main stem and branches. As red pine ages, branch extension and height growth diminish .
Belowground description: Red pine produces lateral roots with vertical sinker roots that are moderately deep and wide-spreading [89,252,266]. It may also produce a taproot extending 0.39 to 10 feet (0.12-3 m) below ground [89,252,252,266]. Lateral roots radiate from the tree in a spoke-like fashion and remain relatively close to the soil surface (4-18 inches (10-45 cm)) . In a review, the lateral roots of red pine were described as being as long as 36 feet (11 m) at a site in Ontario. There were approximately a dozen main lateral roots/tree, and they reached their greatest length in 15 to 20 years . Vertical sinker roots develop from lateral roots to depths of 8.9 to 20 feet (2.7-5.0 m) [47,252,266].RAUNKIAER  LIFE FORM:
Pollination: Red pine is wind- and self-pollinated [46,98]. Self-pollination is restricted by several factors, most important of which is the position of male and female cones in the tree crown. Female cones are generally found in the upper crown and male cones in the lower crown . In closed red pine stands self-pollination probably does not exceed 10%, but the percent of trees that self-pollinate in small isolated stands or in single isolated trees is likely greater (review by ), . Butson and others  state that red pine has a high degree of self-fertility, which assures viable seed production even when trees are isolated.
Breeding system: Red pine is monoecious [98,231,252,266]. Male and female cones generally occur on different branches. Male cones develop at the base of the current year's growth and are tiny and short-lived. Female cones develop in the middle third of the crown in "younger" trees and the upper third of the crown in "older" trees. Red pine, while having a wide geographic distribution, has very low genetic diversity [164,231,303].
Seed production: Under "favorable" growing conditions, red pines produce female cones at age 5 and male cones at age 9 . Red pines produce "good" seed crops at intervals of 3 to 7 years, with "light" crops in most intervening years [4,27,89,166,187,231,252]. Bumper crops occur about every 10 to 12 years [4,22,231,252]. Bumper crop densities of up to 865,000 seeds/ha have been reported in eastern Canada , and as many as 2,263,400 viable seeds/ha have been found in the Great Lakes States .
Less than half the ovules in a red pine cone are capable of developing into seeds. Ovules are found in the central part of the cone and numbers range from 30 to 110 (x=60-90) depending upon cone length and number of scales [231,266]. Cones mature in their second year of growth [80,89,96,252]. In a "good" seed year, trees produce a mean of 45 seeds, with approximately 20 viable seeds/cone; each tree produces 50 to 200 cones or about 1,000 to 4,000 viable seeds/tree [231,252]. Red pine cone production increases as stand density decreases .
Factors influencing cone/seed production: Red pine may begin producing viable seeds at 12 to 60 years of age [4,57,82,89,129,130,187,231,266,320]. Optimum seed-bearing age ranges from 50 to 150 years . Stiell  found that a high number of seed-producing cones occurred in the upper crown and on main branch terminals at Petawawa National Research Forest, Ontario, and Rudolf  stated in a review that cone production is highest on branches that are young, thick, long, and on the south side of the tree. Above-normal temperatures in April, July, August, and September may also favor cone and seed production 2 years later .
On Black Island in Lake Winnipeg, Manitoba, red pine cone production was significantly (P<0.05) positively correlated with tree diameter (R²=0.66), total basal area (R²=0.62), and crown area (R²=0.46). Multiple regression showed the best predictors of cone production were tree diameter and mean distance to neighboring trees. Thus, more cones were produced by large trees growing in an open environment. Further, seed characteristics (number of seeds/cone, mean and total seed mass/cone, and seed size) were significantly positively correlated with cone characteristics (length, diameter, area, and fresh mass, P<0.05). Cone diameter was the cone size variable most strongly correlated with total number (R²=0.73) and mass of seeds/cone (R²=0.80) . Dickmann and Kozlowski  sampled cones from 25- to 30-year-old red pines in Wisconsin. They found a positive association between cone volume and seeds/cone and between number of seeds/cone and scales/cone .
Cone predation: In northern Wisconsin, cones on 105 red pines were studied from 1952 to 1966 . A high proportion of the cones were killed, largely by insects, in all years except the years of heaviest cone production (1954, 1957, 1960, 1963, and 1965). On average, approximately 60% of first-year cones did not survive into their second year . In the Great Lakes States, losses of 20% to 100% of the cone crop have been attributed to red pine cone beetles. Red pine cone moth and red pine coneworm, the other 2 insects that most commonly destroy red pine cones, can cause similar losses when their damage is combined .
Seed dispersal: Red pine seeds are wind-dispersed [111,129,130,266], generally within a radius equal to the height of the seed tree [4,252,266]. The maximum dispersal range is from 900 to 1,000 feet (275-300 m) , with a usual dispersal distance of about 40 feet (12 m) . A few seed-bearing cones may stay in the crown for 2 to 3 years [252,266].
The distance of red pine seedlings from seed trees was measured in Cass and Itasca counties, Minnesota. Seedling density lowered with distance from seed trees :
Red pine seedling establishment by distance from seed trees 
|Distance||Approximate seedling density|
Seed banking: Studies of red pine seed banking were few as of 2008. Ahlgren  studied red pine seed banking in the Boundary Waters Canoe Area. He claimed that red pine seeds may remain viable in the soil for at least 10 years. In the Boundary Waters Canoe Area, Ahlgren extracted red pine seeds from the soil in an area undisturbed for at least 200 years. Seeds were gathered from surface litter to a depth of 1 inch (2.5 cm) and germinated in the greenhouse. Forty-five red pine seeds were procured from a 100-foot² (10-m²) plot, and of those seeds 0% germinated . Two studies state that if rainfall is "deficient", red pine seeds can remain viable for 1 to 3 years before germinating [231,252].
Germination: Red pine prefers a nearly-exposed mineral soil seedbed for germination, which is best prepared by fire [4,11,57,89,94,150,231,252]. Red pine seeds do not have dormancy requirements , and seed viability is variable, ranging from 14% to 65% in the field . Germination occurs close to the soil surface and is best when seeds are covered with a "light" amount of soil .
Light: Shade is beneficial for red pine germination. Seeds may germinate on recent burns with a heavy ash cover, heavy litter or sod, or under dense brush, but shade inhibits growth as seedlings age [45,231,252,266]. Germination is inhibited by full sunlight for 4 or more hours a day .
Red pine seed germination may not be hampered by postfire growth of other vegetation . Two weeks following an 18 June 1981 low-severity prescribed fire, red pine seeds were sown in plots with and without postfire vegetation at Acadia Forest Experiment Station near Fredericton, New Brunswick. Following burning, 2.7 inches (6.8 cm) of organic matter was left and western bracken fern (Pteridium aquilinum) and sheep-laurel (Kalmia angustifolia) began sprouting within 7 days. At the end of the growing season (14 weeks after burning), red pine seed germination was 19.9% (SE 4.80) on sites without western bracken fern and sheep-laurel and 17.1% (SE 5.54) on sites with them .
Seed size: Red pine seed mass may have a positive influence on germination success. Sutton and others  collected seeds from red pines on Black Island in Lake Winnipeg, Manitoba. After 5, 10, 15, 20, 25, and 30 days in the greenhouse, mean germination rates were 0.02%, 53.61%, 89.04%, 89.72%, 90.58%, and 90.92%, respectively. Red pine mean seed mass (R²=0.58) and total seed mass (R²=0.37) were significantly (P<0.05) positively correlated with germination success after 30 days .
Soil and moisture: Red pine prefers a nearly-exposed mineral soil seedbed for germination [4,11,57,94,150,231,252]. Germination is reduced at a soil pH of 8.5 or higher . Moist soil is necessary for red pine germination, which occurs in late spring or early summer . In Minnesota, germination only occurred with mean rainfall of more than 4 inches (100 mm) for May, June, and July. If rainfall is "deficient", seeds may remain viable for 1 to 3 years before germinating [231,252].
Temperature: Red pine germination is best under warm spring and early summer conditions ranging from 61 °F (16 °C) to 86 °F (30 °C) [167,231,252,266]. Seeds may germinate under warm fall conditions, but seedlings do not survive through winter . High temperatures that occur on fire-blackened soil surfaces for the first few years after fire are not conducive to germination, and if germination does occur, lethal to small seedlings [4,252].
In a greenhouse experiment, mean red pine seed germination was 75%. Red pine seed germination began on day 7 and concluded on day 25 of the 30-day experiment .
Seedling establishment/growth: Although red pine germination may not be hampered by other vegetation, successful seedling establishment generally requires little vegetative "competition", adequate light, and mineral soil best prepared by fire [4,231,252,288]. A single red pine seedling growing on Rensselaer Grit Plateau, New York, grew most in a year when the winter was the coldest on record and precipitation was 156% of average . For roughly the first 4 years, red pine seedlings grow less than 10 inches (25 cm) a year. The growth rate increases to 12 to 24 inches (30-60 cm) a year for the next 10 to 20 years [48,252]. Under shaded conditions, it may take a seedling 15 years to reach breast height . Radial growth in red pine may occur for at least 200 years .
Allelopathy/leachate: The release of chemicals by certain understory plants in red pine communities may affect the growth of red pine seedlings. In a Wisconsin plantation, water extracts of leaves from black cherry (Prunus serotina), red raspberry (Rubus idaeus), bigleaf aster (Eurybia macrophylla), Tatarian honeysuckle (Lonicera tatarica), climbing nightshade (Solanum dulcamara), and giant goldenrod (Solidago gigantea) reduced red pine height growth, number of secondary needle fascicles, weight increments of roots and shoots, and radicle elongation of red pine seedlings . Laboratory results may differ from the effects of natural concentrations of plant chemicals occurring in the field.
Leachate from red pine and sheep-laurel litter significantly reduced growth of red pine seedlings in sand compared to seedlings growing in burned-over mineral soil . Red pine seedlings were grown for 8 months in sand, sand watered with either red pine or sheep-laurel leachate, and burned-over mineral soil. The leachate experiments might have mimicked red pine seedling growth in red pine or sheep-laurel litter. After 8 months, red pine seedlings grew significantly better in the burned-over soil than in the other 3 treatments. There were no significant differences in growth between seedlings exposed to sheep-laurel leachate and those exposed to red pine leachate, though seedlings in the sand without leachate grew significantly better than seedlings exposed to leachate .
|Growth of red pine seedlings in sand, burned-over soil, and sand watered with either red pine or sheep-laurel leachate |
|Treatment||Average plant height (cm)|
|Initial planting||8 months later|
|Sand with sheep-laurel leachate||5.7a||9.6c|
|Sand with red pine leachate||5.8a||11.3bc|
|Values within a column followed by different letters are significantly different (P≤0.05).|
Fire: Fire is very important in creating the conditions necessary for red pine seedling establishment (an exposed mineral soil and little vegetation). Removing the organic layer and exposing mineral soil requires a moderate to severe fire [94,288]. Red pine seedling growth is inhibited following fires that leave a thick ash layer . Low-severity surface fires do not promote red pine seedling recruitment because they do not expose mineral soil. Seedling establishment requires local flare-ups that remove patches of vegetation, creating a mosaic of even-aged patches . Given that red pine produces "good" seed crops every 3 to 7 years and bumper crops every 10 to 12 years (see Seed production), the probability of good seed years coinciding with desirable postfire seedbeds is low, making adequate postfire seedling establishment infrequent . Red pine needs about 3 postfire years without "competing" vegetation to dominate a site .
In a controlled experiment, red pine seedling emergence was high with high soil moisture, low soil organic matter content, and shade, but low on ash substrates . The researchers collected soil monoliths within a jack pine-red pine-eastern white pine community from the Great Lakes-St Lawrence Forest. Soil was taken to a laboratory and subjected to 4 organic horizon removal treatments (100%, 75%, 50%, and 25% organic horizon removed). The monoliths were then burned, subjected to 4 ash removal treatments (100%, 75%, 50%, and 25% ash layer removed), and seeded to red pine. Following seeding, the monoliths were moved to a greenhouse and subjected to 4 watering regimes (100%, 75%, 50%, and 25% of average daily June rainfall) and 4 shading regimes (100%, 75%, 50%, and 25% of photosynthetically active radiation (PAR)). Bar graphs show the effect of organic horizon removal with and without ash under the 75% and 100% water regime and the 4 shading regimes .
Red pine seedling establishment on a burned site was much greater than on an unburned site in Newfoundland . Both sites were on dry, sandy soil and approximately 14 miles (22 km) apart. The organic matter depth was apparently the most important factor controlling seedling establishment. As organic matter deepened, seedling establishment was reduced . Time between the July 1979 fire and red pine seedling measurements was not provided. Presumably, since red pine only produces good seed crops every 3 to 7 years and the age of seedlings on the burned site ranged from 2.4 to 2.9 years, the study was conducted 6 to 10 years after fire.
|Red pine seedling establishment characteristics on burned and unburned sites in Newfoundland |
|Distance from seed-bearing trees (m)|
|Number of seedlings||19||45||28||8|
|Organic matter depth (cm)||2.0||2.1||2.6||2.8|
|Number of seedlings||0||2||2||7|
|Organic matter depth (cm)||---||4.0||5.0||2.7|
Establishment in an undisturbed forest: Red pine seedlings generally establish after fire prepares a mineral seedbed. However, on the shore of Basswood Lake, Ontario, Ahlgren  found seedlings, saplings, and mature, seed-producing red pine growing in a 200-year-old undisturbed red pine forest. Thus, seedling establishment may occur in the absence of fire.
|Average number of red pine seedlings, saplings, and seed-producing trees in a 200-year-old undisturbed red pine forest |
|Years since disturbance||Seedlings/acre||Average seedling age (years)||Average seedling height (feet)||Saplings/acre||Seed-producing trees/acre|
Growth with associated vegetation, light, shading: Shade provided by associated vegetation is beneficial for germination and early survival of red pine seedlings but inhibits growth as seedlings age [28,45,149,252]. Root penetration by red pine is generally slower than that of associated vegetation; thus, red pine seedlings may be less tolerant of competition [231,252].
Red pine seedling growth is reduced by beaked hazelnut (Corylus cornuta subsp. cornuta) and American hazelnut (C. americana) . During a 2-year study, 100% of red pine seedlings growing without hazelnut cover survived, but only 62% survived with hazelnut. Red pine seedlings grew an average of 5.9 inches (15 cm) when not shaded and 2 inches (4 cm) when shaded by hazelnut during year 2 of the study. At the end of the study, seedlings growing with hazelnut averaged 1.9 g (SD 0.9) dry weight, while seedlings growing without hazelnut averaged 7.0 g (SD 2.8) dry weight. The researcher notes that while both shading and moisture competition affected red pine seedlings growing with hazelnut, shading was the most important factor. Moisture levels were not directly measured, but it was assumed that seedlings that were trenched and watered received more moisture than untrenched, unwatered control seedlings .
On the Chippewa National Forest, Minnesota, Shirley  found that red pine seedlings grew poorly in an undisturbed 43-year-old quaking aspen stand. In 1931, 2-year-old red pine seedlings were planted in quaking aspen stands that had either been left undisturbed or had their understory removed mechanically. By 1934, red pine seedling mortality in the undisturbed plot was 60.7%, while mortality was only 9.7% in the understory removal plot .
Red pine seedlings grow better without than with other vegetation north of Sault Ste Marie, Ontario . Following clearcutting of a forest site, red pine seedlings (mean height=3.6 inches (9.2 cm), mean stem diameter=3.1 mm) were planted in plots with naturally-occurring vegetation (western bracken fern, false melic (Schizachne purpurascens), roughleaf ricegrass (Oryzopsis asperifolia), violets (Viola spp.), and low sweet blueberry) either removed annually by herbicides or left untreated. At the end of 5 years, red pine seedling survival, height, stem diameter, stem volume, and survival rate were greatest on sites where associated vegetation was controlled .
Red pine seedling characteristics on sites with and without other vegetation 
|With vegetation||Without vegetation|
|Stem diameter (mm)||1.95||3.72|
|Stem volume index (cm³)||400.1||1,792.8|
|Height, stem diameter, and stem volume were significantly lower on sites with than sites without vegetation (P<0.05).|
Red pine seedlings grow best in full sunlight. In an experiment, Logan  grew red pine seedlings in reduced to full sunlight gradients for 4 to 6 years. Growth and biomass gains increased with increasing sunlight .
Growth characteristics for red pine seedlings grown in 4 levels of lights for 4 to 6 years 
|Growth characteristic||Light level (percentage of full sunlight)|
|Shoot weight (g)2||1.4||4.4||12.1||23.5|
|Foliage weight (g)3||4.3||23.8||84.5||198.1|
|Branch weight (g)3||0.2||2.7||19.3||58.3|
|Stem weight (g)3||1.2||7.5||25.3||56.3|
|Root weight (g)2||0.6||1.7||7.1||14.9|
|Needle length (inches)1||3.2||4.1||3.9||3.9|
|Leader diameter (mm)1||2.3||3.8||4.9||5.9|
|Root crown diameter (mm)4||4.2||8.6||14.8||22.5|
|1Following 5 years of growth; 2oven dry weight following 4 years of growth; 3oven dry weight following 6 years of growth; 4following 6 years of growth.|
Shirley  conducted a similar study on the Chippewa National Forest, Minnesota, from 1931 to 1934. As with the above study, red pine seedlings performed better with increasing amounts of sunlight .
Despite its need for sunlight, red pine apparently does not require an open stand structure. Red pine sapling height was positively correlated with density on the Chippewa National Forest (r=0.609) . On plots where red pine saplings were spaced approximately 20 × 20 feet (6 × 6 m) apart, average height was 5.5 feet (1.7 m), while saplings spaced as close as 5 × 5 feet (2 × 2 m) apart, average height was 14 feet (4.3 m). Further analysis showed that trees of the same height grew more rapidly during the following 10 years if they were located within 5 feet (2 m) of another tree than trees spaced more than 5 feet (2 m) apart .
Heat tolerance: Red pine seedlings are susceptible to heat mortality [175,245]. Red pine heat tolerance was investigated using 1- to 4-year-old seedlings exposed to various temperatures for 1 to 30 minutes. Following the heat treatments, percent red pine seedling cell mortality was measured. Cell mortality began at 133 °F (56 °C) exposure for 30 minutes. The maximum temperature that 100% of cells survived was 140 °F (61 °C) for 1 minute . In a nursery, Shirley  investigated lethal temperatures to buds, needles, stems, and roots of red pine seedlings. At 2 hours of exposure, buds, needles, and stems were all killed at temperatures of 119 to 124 °F (48.2-51.3 °C). Root mortality occurred at 114 to 123 °F (45.7-50.3 °C). Lethal temperatures were similar but slightly lower for buds, needles, and stems after 5 hours of exposure .
Height growth: Red pine grows optimally where it receives at least 6 hours of direct sunlight daily. Red pine growth is "very uniform". Under favorable conditions, it increases in height approximately 10 inches (30 cm) a year for the first 60 years. Maximum height is usually attained by 60 to 120 years of age .
Seedling facilitation: Northern red oaks on a stable dune system by Lake Huron, Ontario, facilitated establishment and growth of red and eastern white pine seedlings . In a comparison of open areas and stands of northern red oak older than 35 years, densities of eastern white pine and red pine juveniles were over 6 times greater under northern red oak than in open areas (P<0.001). Further, average pine stem density was significantly greater beneath the northern halves of northern red oak canopies (1.00 stems/m², SD 0.07) than under the southern halves (0.33 stem/m², SD 0.30) (P<0.01) .
Shoot/root growth: Old needles (>1 year) provide 80% or more of carbohydrate reserves used to support new shoot growth. Branches, main stem, and roots, in that order, provide the other major sources of carbohydrate reserves for shoot growth [155,311].
Red pine has 2 primary periods of root growth: the 1st occurs in spring and early summer, the 2nd in early fall [252,266]. Roots develop best in loose soil and worst in soils that are saturated, compacted, and/or coarse-textured or are strongly stratified, fine, and/or overlay coarse-textured soils . Root development is fostered by a water table within 3.9 feet (1.2 m) of the soil surface . Mortality occurs if roots are in soils saturated for more than 3 months . Red pine roots can grow around stones and penetrate cracks in bedrock on shallow soils. Root size increases the first 15 years of life; afterwards, root density increases .
Red pine germination did not differ by soil type, but root and shoot growth was significantly better in sand than in organic matter or Ae horizon soil. Red pine primary root and shoot lengths were measured 3 weeks after germination .
|Effect of forest floor substrates on red pine root and shoot growth |
|Values within a column followed by different letters are significantly different (P≤0.05).|
Soil/moisture: Red pine seedlings grow best in sand to sandy loam soil  that has good moisture retention, is well aerated, has high cation exchange capacity, and pH ranging from 5.1 to 5.5 [231,252]. Seedlings perform poorly on calcareous soils . While preferring moist soil, red pine seedlings have been found growing on dry, nutrient-poor sites in Itasca State Park .
Seedling mortality: Young seedlings are susceptible to drought, insolation, freezing temperatures, flooding, and rodent browsing [167,252,266].
Vegetative regeneration: Red pine does not regenerate vegetatively [231,252].SITE CHARACTERISTICS:
Climate/weather: Red pine is native to areas with cool to warm summers, cold winters, and low to moderate precipitation. Within its range, average January temperatures vary from 0 to 25 °F (-18 to -4 °C), and average July temperatures vary from 60 to 70 °F (16-20 °C). Average annual maximum temperatures range from 90 to 100 °F (32-38 °C) and average annual minimum temperatures from -10 to -40 °F (-23 to -40 °C). Average annual precipitation is from 20 to 40 inches (510-1,010 mm) throughout much of its range, but reaches 60 inches (1,520 mm) in some eastern localities. The average growing season precipitation ranges from 15 to 25 inches (380-640 mm), and average annual snowfall ranges from 40 to 120 inches (1,000-3,000 mm). Summer droughts of 30 or more days are common in the western half of red pine's range. The frost-free period is from 80 to 160 days, though it may be as short as 40 days northeast of Lake Superior in Ontario [48,97,101,106,137,231,266].
According to research in Chippewa County, Michigan, precipitation is closely related to radial growth in red pine throughout the growing season. Warm spring temperatures initiate the growing season but have little effect on radial growth. Dils and Day  found prolonged dry periods caused a leveling off of radial growth. Red pine radial growth immediately began to increase with the onset of "significant" precipitation .
Drought: While regeneration in red pine is most dependent upon fire, climate may also be a factor. Above-normal temperatures, alternating with periods of freezing and thawing, may kill seed; and seedlings may be damaged by frost and desiccation. Bergeron and Brisson  studied the effect of temperature and precipitation on red pine regeneration from 1913 to 1986 at Lac Duparquet in northwestern Quebec. Regeneration was positively correlated with above-average precipitation. On an island site, red pine regeneration was negatively correlated with above-average temperature (P<0.05). The researchers noted that drought limited red pine regeneration most .
Mature red pine is drought tolerant , but needles may turn reddish brown when very dry conditions persist over several growing seasons. Red pine mortality may occur during "severe" drought .
Frost: Young red pines are susceptible to spring frost, which can severely damage or kill new growth. Sites where frost damage is most likely include depressions and breaks where air drainage is limited and on exposed, dry sand flats where rapid cooling occurs at night [252,266]. Sakai and Weiser  found that mature trees in northern Wisconsin were highly resistant to freezing. Laboratory tests showed that dormant buds, leaves, and twigs from mature trees were uninjured to temperatures of -200 °F (-80 °C) .
Flooding: Red pine can survive temporary flooding, but flooding reduces growth. Ahlgren  studied the effect of temporary flooding on red pine at Basswood Lake, Ontario. He found that red pines in the 1- to 4-foot (0.3-1 m) size class suffered greater terminal growth stunting and slower crown recovery than trees in the 5- to 12-foot (2-4 m) class. Trees in the flooded area were submerged in at least 4 feet (1 m) of water for 20 to 48 days during May and June. All sizes of red pine had at least a 90% survival rate when flooded for 28 days or less. Red pines in the 5- to 12-foot (2-3.7 m) class had a better than 90% survival rate at sites flooded for up to 48 days .
Wind: Red pine is susceptible to wind damage . Following two July 1983 windstorms in a pine/maple (Pinus spp./Acer spp.) and pine/fir (Abies spp.) community in Itasca State Park, red pine suffered some mortality. While not directly measured, wind speeds likely reached 60 to 75 mph. Red pine was the dominant overstory tree in both communities, constituting 39.4% of total basal area in the pine/maple forest and 36.1% of total basal area in the pine/fir forest. The windstorm killed 0.6% of all red pines in the 100-acre (40-ha) pine/maple study area and 0.7% of all red pines in the 5-acre (2-ha) pine/fir study area .
Global climate change: Gradual climate warming is predicted to temporarily increase red pine abundance but eventually lead to decline. He and others  modeled the effect a 9 °F (5 °C) increase in temperature would have on trees characteristic of northwestern Wisconsin over a 100-year period. They extended their model out an additional 200 years, with the mean annual temperature held constant at the 100-year period increase. Current red pine cover is 8%; the model predicts it will increase with warming to 18% due to the decline of northern hardwood species. However, after 300 years of increased temperatures, the model predicts red pine cover near 0% . Other models suggest that a substantial decline in red pine will occur throughout its range if annual temperatures increase from 2.7 °F to 8.1 °F (1.5-4.5 °C) by the end of the 21st century [207,208].
Models predict that future warming of 0.03 °F (0.02 °C)/year in summer and 0.05 °F (0.03 °C)/year in winter will cause the eventual extinction of red pine in northern Michigan after about 400 years. Red pine will likely be replaced by maples, ashes, oaks, and eastern hemlocks .
Northern range: At the northern edge of its range, red pine is restricted to lake landscapes and rough topography . Red pine may have low cone and seed production at its northern limit [34,92]. However, Sutton and others  found this was untrue on Black Island in Lake Winnipeg, Manitoba. In the year 2000, they found red pine produced from 50 to 200 cones/tree, which is well within its normal range at lower latitudes. Further, red pines produced cones during 3 successive years (1999-2001). The researchers also found that reproduction characteristics (cone length, seeds/cone, and germination success) were well within the normal range found in southern climes .
Elevation: Red pine typically grows from 700 to 1,400 feet (200-430 m) in elevation [23,96,97]. In New England it is found up to 2,000 feet (600 m) , in New York up to 3,480 feet (1,060 m) , and in West Virginia it may occur at over 4,000 feet (1,200 m) .
Soils: Red pine grows best on well-drained, aerated sandy to loamy soils, typically of glacial outwash origin [22,23,59,79,80,92,157,157,243,281]. It is most common on Entisols, followed in order by Spodosols, Alfisols, and Inceptisols . Red pine can grow on poorly-drained sands . However, there is a great chance of root stunting and mortality where it grows on poorly-drained soils . It may also grow on heavy soils, but its growth is impeded by hardwood species that favor such soils . Red pine performs best where the water table is from 4 to 9 feet (1-3 m) below the soil surface .
In red pine old-growth stands in the Great Lake States, the organic layer seldom builds up to a depth greater than 2 to 6 inches (5-15 cm) [79,144,231].
Red pine grows poorly on potassium-deficient soils , but can grow on soils deficient in nitrogen and phosphorus . The optimum soil pH range for red pine is from 5.2 to 6.5, but it can grow on soils with pH of 4.0 to 7.5 [165,252,266].
|Minimum red pine soil growing requirements on well-drained soils |
|Organic matter (%)||1.3|
|Exchange capacity (me/100 g)||3.5|
|Total N (%)||0.05|
|Available P (kg/ha)||28.0|
|Available K (kg/ha)||78.0|
|Exchangeable Ca (me/100 g)||0.80|
|Exchangeable Mg (me/100 g)||0.20|
In northern Lower Michigan, red pine's occurrence in quaking aspen-dominated stands is largely determined by soil. Red pine is found only on dry-mesic sites with sandy upland soils. Red pine declines in quaking aspen communities as soils become moister and heavier .
Erosion: Reduced growth occurs in red pines growing on eroded sandy soil. Farrish  measured the basal area, diameter, and height of 46-year-old red pines growing in eroded and uneroded sandy outwash soil in Newaygo County, Michigan. Soil thickness on uneroded sites was approximately 26 inches (66 cm) and on eroded sites was near 10 inches (25 cm). Basal area of red pine averaged slightly less on eroded than uneroded sites. Diameter and height of red pine were significantly less on eroded than on uneroded sites (P<0.003) .
Associated species by soil type: On coarse, dry soil, common associates include jack pine, quaking aspen, bigtooth aspen (Populus grandidentata), paper birch, northern pin oak (Q. ellipsoidalis), and bear oak (Q. ilicifolia) [22,23,31,50,79,114,231,252]. On fine to loamy sands, in addition to the foregoing, red pine is associated with eastern white pine, red maple, black cherry, northern red oak, white oak (Q. alba), chestnut oak (Q. prinus), balsam fir (Abies balsamea), and black spruce (Picea mariana) [22,23,31,79,231]. On sandy loam and loam soils, red pine associates include sugar maple (Acer saccharum), eastern white pine, basswood (Tilia americana), red maple, balsam fir, paper birch, yellow birch (B. alleghaniensis), American beech (Fagus grandifolia), northern red oak, eastern hemlock (Tsuga canadensis), white spruce (P. glauca), white ash (Fraxinus americana), red spruce (P. rubens), northern white-cedar (Thuja occidentalis), and eastern hophornbeam (Ostrya virginiana) [23,50,79,231].
At Lake Itasca State Park, Minnesota, red pine is likely an edaphic climax species. Sterile, sandy soils were colonized by herbs, shrubs, and jack pine. Red pine began to establish as jack pine improved soil conditions by adding organic matter and thus improving soil moisture holding capacity. Eventually jack pine-red pine communities transitioned into pure red pine stands, since jack pine has a shorter life cycle and is less tolerant of shade than red pine. At the time of study, red pine was failing to reproduce and being replaced by sugar maple, balsam fir, and white spruce .SUCCESSIONAL STATUS:
Early succession: Red pine is often an early successional species throughout its range. It is an early and late successional or "subclimax" species on sand dunes near Lake Michigan. In Wilderness State Park along the shore of Lake Michigan, red pine stands begin to develop when dunes are approximately 145 years old. Red pine stands dominate dunes carbon dated to 345, 400, 1,975, and 2,375 years old. Red pine cover is greatest on the oldest (2,375) dune formations . Red pine is a seral species in the sand ridge region along Lake Michigan, occurring in the early-successional pine-oak (Quercus spp.) stage. The pine-oak stage is preceded only by an herbaceous stage formed on unstable sand dunes. Eastern white pine and red pine likely remain through late succession [306,307].
In the Great Lakes region in the upland boreal and boreal conifer-hardwood forests, red pine, paper birch, Populus spp., jack pine, and eastern white pine are considered the most important species in early-successional habitats with low moisture and abundant light .
Fire: Fire plays the greatest role in the succession of red pine. Since red pine depends on fire to create the conditions necessary for establishment, it occurs as a postfire pioneer species [77,181]. Red pine is often considered a "fire-maintained climax" species [11,79,109,190,261]. Red pine is eventually replaced in the absence of fire. In the south of its range it is eventually replaced by hardwood species and by shade-tolerant conifers in boreal forests . In the Great Lake States, succession may be from jack pine to red pine to eastern white pine and finally to northern hardwoods. On infertile, sandy sites, succession may end before hardwoods establish, and red pine may persist at a subclimax stage. In the eastern portion of its range, red pine may be a successional stage in a spruce-fir or eastern hemlock climax, rather than a northern hardwoods climax . At red pine's northern limit in the southern boreal forests, frequent severe fires discourage red pine establishment by killing trees before they reach seed-bearing age and favor jack pine and black spruce [30,230].
The successional trend of red pine's replacement by other less fire-tolerant species is well established. The table below provides more regionally and/or species-specific information on this process. In all cases, red pine was one of the primary early-seral tree species.
Red pine succession in the absence of fire by region
|Location/site characteristics||Red pine's replacements||Time to displacement||Other notes|
|northern Minnesota||balsam fir, birch (Betula spp.)-aspen, fir-spruce (Picea spp.)-birch, or maple-basswood||not given [142,148]||---|
|Boundary Waters Canoe Area, Minnesota||black spruce||400-450 years [127,128]||---|
|Great Lakes-St Lawrence||white spruce, balsam fir, paper birch, black spruce, northern white-cedar, and red maple||300-400 years||red pine still dominant after 300 to 400 years, and replacements are still in understory [130,252]|
|Acadia National Park, Maine||red spruce||not given||fire exclusion considered the cause of decreased red pine abundance |
|Lake Duparquet, southwestern Quebec; xeric sites along lake shores||northern white-cedar, black spruce||not given ||---|
|southern Ontario||white birch, balsam fir, black spruce||not given ||---|
Late-seral forests/logging: Aggressive logging combined with reduction in the natural fire frequency with European settlement led to a decrease in red pine abundance in the Great Lakes States. Several authors noted that logging and repeated slash burning in the mid- to late 1800s "virtually eliminated" red pine [10,122,130,163,173,209,298,299]. Nearly complete removal of mature seed-bearing trees stifled regeneration [173,209].
Red pine-eastern white pine forests comprised 97,703,000 acres (39,539,000 ha) in 1850 just prior to settlement; in 1995, red pine-eastern white pine forests were found on only 20,500,000 acres (8,310,000 ha) . There were approximately 509,000 acres (206,000 ha) of old-growth, late seral red pine-eastern white pine forests in the Great Lake States in the 1980s and 1990s. An estimated 9,600,000 acres (3,900,000 ha) were old-growth, late seral red pine-eastern white pine forests up to 8,000 years before settlement. The researcher claimed that reduced fire frequency was as much to blame for the decrease in red pine cover as overlogging . In northern Minnesota in the late 1800s, red pine was codominant to dominant on 8.3% to 16.6% of forests. Dominance or codominance decreased to 0.79% to 3.56% in 1990. In northern Minnesota forests, logging has replaced fire as the major disturbance, causing a successional shift to hardwoods .
If an adequate seed source is readily available, red pine may establish after logging. Logging can expose mineral soil, creating favorable seedbed conditions for red pine [4,152]. Red pine seedlings probably establish when mature red pine areas are logged soon after a good seed crop develops, and logging is followed by slash burning. In northern Michigan, red pine sites heavily logged and burned contain red pine seedlings and saplings, but nevertheless juvenile red pines may be "outcompeted" by white oak, northern pin oak, northern red oak, black oak, and scarlet oak .
With a seed source, red pine can spread into logged areas. Near Found Lake in northeastern Wisconsin, large tracts of eastern white pine and red pine were logged from 1890 to 1894, and slash burning occurred from 1894 to 1897. For about 80 years following logging and burning, white birch, bigtooth aspen, and quaking aspen dominated the sites. Some red pines in isolated pockets were not logged. Red pine is now reclaiming dominance in some areas. Basal area of red pines with a DBH of 4 inches (10 cm) or greater increased from 2.99 m²/ha in 1950 to 10.1 m²/ha in 1997 .
Following settlement, red pine stands in the Great Lakes States were clearcut or cut leaving 1 to 8 seed trees/acre. On mesic sites other vegetation, particularly beaked hazelnut and balsam fir, interferes with red pine establishment. The average age of red pine stands has declined from an average of 230 years during the presettlement period to 72 years (review by ).SEASONAL DEVELOPMENT:
Seed dispersal generally occurs a few days after ripening (mid-August to October) and continues throughout fall and into the next spring. Most seeds are dispersed within a month of ripening, with a few seeds remaining on the tree for 2 to 3 years [252,266]. Red pine cones open and disperse seeds best on warm autumn days [4,231,266].
At Stephentown, New York, the growing period for a 5-year-old seedling ranged from 45 to 63 days over 5 years, beginning near the end of April and ending about the end of June . At the same location, Cook  observed the growth period for a 7-foot-tall (2 m) red pine during 1940. Growth began on 7 May and ended 7 July, for a total of 61 days. During the growing period, the red pine tree increased in height by 17.5 inches (44.4 cm) .Seedling root development: The seasonal root development of 2- to 3-year-old red pine seedlings was observed near Syracuse, New York, for 1 year . The study began in January, when the roots were dormant. Roots remained dormant until late April or early May. Root growth began approximately a week before separation of the bud scales in the terminal leader of the shoot. The peak of spring root growth occurred during June, followed by a slow period of growth in July and August when soil moisture was decreased. Root growth increased again in late summer or early fall, depending upon soil moisture conditions. Root growth phenology of 20- to 30-year-old trees was similar to that of seedling root growth .
Bark: Red pine bark thickness is its most important fire adaptation. At maturity (beginning at age 20-40), red pine's fire-resistant, thick bark helps protect it from surface fires of low to moderate severity [4,46,51,94,95,125,126,141,147,288] and possibly high-severity fires . By the time red pine produces seed, it is not generally killed by surface fires [56,57]. In Pennsylvania and the Great Lakes States, maximum red pine bark thickness ranges from 5.0% to 5.2% of DBH . Butson and others  claim that the unusually fire-resistant bark makes crown scorch the greatest limitation to red pine survival during fire. Bergeron and Gagnon  state "long-term maintenance of red pine is promoted by fire because its thick bark effectively protects it against most surface fires of light to moderate intensity, whereas its shade-tolerant competitors are usually killed." Bark of young trees (<20-40 years old) is relatively flammable, however [3,230].
Crown fires/scorch/structure: Mature red pine have an elevated crown and are self-pruning [115,147,192], which helps protect them from surface fires spreading into the crown [115,147,192,252]. Crown fires are much more likely in young red pine stands (15-20 years of age), where crowns are closer to the ground [3,129,130]. The nonconical shape of red pine crowns also limits the rate of spread and crowning of fires. It generally takes windy, dry conditions for crowning to occur .
Crown scorch kills red pine more often than stem damage , though high intensity fires can cause cambial injury [72,134]. While red pine can survive low- to moderate-severity surface fires, severe surface fires can cause crown scorching [72,134]. Mortality begins at 46% to 50% crown scorch. Two groups have published guidelines for predicting mortality from crown scorch: the first states that there is a 50% probability of tree mortality if 81% to 85% of the crown scorches , while the second states that most red pines die when more than 75% of the crown is scorched [72,134]. Trees have a better chance of survival following crown scorch if scorch occurs before bud flush . A surface fire of less than 200 BTU/sec-ft will probably not scorch the crown of red pine, a surface fire of 500 BTU/sec-ft is "on the edge of dangerous" for the largest red pines, and a surface fire of 1,000 BTU/sec-ft is likely to kill most red pines .
Regeneration following fire: Red pine's only regeneration method following fire is by seed from crown-stored cones or off-site sources [4,22,80,89,96,166,187,230,231,266]. However, red pine seeds are generally dispersed within a radius equal to the height of the seed tree [4,252,266], with a maximum dispersal range from 900 to 1,000 feet (275-300 m)  and a mean dispersal distance averaging about 40 feet (12 m) . Thus, regeneration is most likely to occur from crown-stored seeds not damaged by fire. Red pine requires 20 to 40 years between fires for successful recruitment [55,57].
Resin: Following fire wounding, red pines produce a large amount of resin that fills the wounds [11,236,294]. It is hypothesized that this is an adaptation to prevent the entrance of wood-destroying fungi and bark beetles. Verrall  found few wood-decaying organisms in heavily-wounded red pines at Cloquet Forest Experiment Station, Minnesota. The trees, approximately 110 years old, were wounded by fires in 1842, 1853, 1864, and 1894. Wounds extending one-eighth to one-fourth the circumference at the base of the tree and 6 to 10 feet (2-3 m) up the stem were common. Yet a large majority of trees were entirely free of decay .
Fire regimes: Substantial evidence suggests that a "natural" fire regime is necessary for the maintenance and perpetuation of red pine stands [11,28,32,94,127,128,129,130]. Red pine generally occurs in even-aged stands experiencing frequent understory fires and infrequent, stand-replacement fires [2,23,258,259]. Fires not only reduce shrub vegetation that competes with red pine seedlings, but also improve the seedbed by reducing forest floor depth [9,94,95]. According to Heinselman , red pine has 2 distinct fire regimes. The 1st fire regime occurs in Minnesota, Wisconsin, and western Ontario in red pine and red pine-eastern white pine stands with little understory development, almost no shade-tolerant conifers or hardwoods, and a xeric climate. These forests probably had a history of periodic "light" surface fires at 5- to 50-year intervals, plus high-severity fires at longer intervals that resulted in a new cohort of pines . In this literature review, a discussion of this red pine fire regime theory is presented first, and Heinselman's 2nd fire regime theory for red pine stands occurring from Michigan eastward is discussed second. Heinselman's 2nd fire regime theory is contradicted, in part, by other literature [173,174,250]. This discussion is followed by the effects of fire exclusion and climate change on red pine.
Xeric sites/red pine dominant: In the western part of the Great Lakes-St Lawrence-Acadian forests of Minnesota, Wisconsin, and western Ontario, surface fires of moderate intensity historically occurred at intervals of 20 to 40 years in red pine and red pine-eastern white pine forests [38,79,130,131]. High-severity, stand-replacement fires historically occurred at intervals of 150 to 300 years [27,31,38,79,129,130,131,132,140]. Red pine also occurs with jack pine. Red pine-eastern white pine-jack pine communities, which occur within both xeric and mesic red pine regions, likely had historic low- to moderate-severity fires at intervals of 29 to 37 years  and high-severity, stand replacing fires at intervals of 100 to 300 years [141,220,313]. Most of the research that follows focused more on surface fire-return intervals for red pine and less on stand-replacement fire-return intervals.
The Boundary Waters Canoe Area contains some of the largest remaining stands of red pine . Red pine and eastern white pine commonly occur on islands or on the east, north, northeast, or southeast sides of lakes, streams, swamps, or valleys in the area. Fires commonly ignite as spot fires and then burn as backfires, creeping down to the lakeshore or swamp edge. The entire Boundary Waters Canoe Area had a natural fire rotation (average time required to burn and regenerate an area equivalent to the whole 1,000,000-acre (400,000-ha) virgin forest study area) of 100 years from 1595 to 1910. The areas dominated by red pine and eastern white pine were likely to sustain surface fires at average intervals of 36 years during this period (1595-1910). Since other trees in the area are so fire sensitive, surface fires killed them, allowing for red pine regeneration. High-severity, stand-replacement fires in red pine communities likely occurred at intervals of 150 to 300 years. Heinselman [127,128] states that some red pines in the Area have escaped fire mortality for 400 to 500 years, providing an important seed source. However, Swain  studied red pine stands across the Boundary Waters Canoe Area and found no trees that had escaped fire for longer than 202 years. The main red pine overstory stand at Boulder Bay established following a 1681 fire and then partially burned in 1755 and 1767. Swain was able to create a fire history of the area beginning in 1595 with a 378-year-old red pine .
Itasca State Park also contains a large population of red pine. The oldest red pine stands in Itasca State Park originated from widespread fires around 1714 [259,260]. Younger stands originated from a 1772 fire. The major present-day stands of red pine originated from fires in 1803, 1811, and 1820. Smaller stands of red pine in the park are from the last 2 large fires in the Park, which occurred in 1865 and 1886 [259,260]. The understory fire-return interval at Itasca State Park for 50-year periods is presented below. Settlement began in the late 1800s and coincided with an increased fire frequency due to land clearing and logging fires. There have been no major fires in the park since 1918 [103,104].
|Understory fire-return intervals in Itasca State Park, Minnesota (1650-1922) [103,104]|
|Time period||Average fire-return interval|
At Deming Lake in northwestern Minnesota, Clark  estimated mean fire-return intervals via fire scar and charcoal stratigraphy data in mixed forests of red pine, eastern white pine, jack pine, and hardwoods. Overstory hardwoods were primarily paper birch, Populus spp., sugar maple, red maple, and northern red oak. The mean fire-return interval was 13.2 years during 1240 to 1440, when the climate was cool and moist, and decreased to 8.6 years during 1440 to 1640, when the climate was warm and dry. The average interval increased to 13.5 years with the occurrence of the "Little Ice Age" from 1640 to 1910. Fire has been excluded in the area since 1920 .
Two fire history studies were conducted near the dividing line between xeric and mesic red pine communities. Using fire scar data, a 247-year-old red pine tree taken near Pointe aux Pins in Parke Township, Ontario, in 1978 showed a mean understory fire-return interval of 29 years, with a range of 14 to 46 years, for 1727 to 1877. Fire has not burned through the area in over 100 years . In south-central Ontario, Dey and Guyette  estimated the understory fire-return interval for 2 periods in a site dominated by red pine, eastern white pine, gray birch (Betula populifolia), and quaking and bigtooth aspen. Prior to European settlement (1636-1779), the fire-return interval was greater than 117 years. With settlement, the fire-return interval decreased to 17 years from 1780 to 1940 .
Mesic sites/red pine dominant and nondominant: Heinselman's  2nd fire regime for red pine occurs in eastern white pine stands with less red pine and a large amount of eastern hemlock, white or red spruce, balsam fir, northern white-cedar, sugar maple, beech, yellow birch, and/or red maple. These sites are more mesic than the former and occur from Michigan eastward. According to Heinselman, this forest type was more likely to have stand-replacement fires at long intervals (150-300 years) . Two other researchers claim that historic stand-replacement fire-return intervals for red pine from Michigan eastward ranged from 150 to 350 years [62,116]. However, much of the research presented below indicates that mesic red pine experienced understory fire-return intervals similar to those in xeric communities.
Drever and others , working in the Great Lakes-St Lawrence forest of Temiscamingue, Quebec, provide the only research substantiating the theory that long fire-return intervals occurred in red pine communities in mesic sites. The researchers estimated the fire-return interval for the period 1591 to 2004 was 213 years (SE 8). The researchers identified 3 distinct fire cycles: presettlement (1591-1880), settlement (1880-1924), and postsettlement (1924-2004). Presettlement times were characterized by a long fire cycle, which turned to a shorter fire cycle during settlement, then returned to a longer fire cycle during the postsettlement period. Isolating only pine-dominated sites (red pine and eastern white pine), the mean fire-return interval for 1591 to 2004 was approximately 165 years .
During the summers of 1984 and 1985, Loope  constructed a pre- and postsettlement fire history of Pictured Rocks National Lakeshore, Michigan. Red pine, eastern white pine, and jack pine are primarily found along shoreline areas and major embayments. Prior to settlement, nonlethal understory fires occurred at intervals of 28.2 years in pine stands containing red pine. Following settlement, understory fires decreased. The fire-return interval in red pine stands increased to 77 years in the 20th century . Loope and Anderton  constructed a presettlement (before 1910) fire history for 39 small red pine communities in isolated, coastal sand patches along the upper Great Lakes. Understory fire-free intervals before 1910 at the 39 sites ranged from 7.7 to 32.0 years, with an overall average of 18.4 (SD 11.5) years. After 1910, the fire-free interval increased dramatically, ranging from 66 to 138 years, with an average of 88.4±14.8 years. The researchers also constructed a presettlement fire history for 4 upland sand plain red pine sites near Raco, Michigan. Understory fire-free intervals before 1910 ranged from 13.0 to 29.0 years, with an average of 23.0±13.8 years. After 1910, the understory fire-free interval increased slightly, ranging from 19.2 to 64 years, with an average of 29.3±26.7 years .
Following the 5 May 1980 Mack Lake Fire in northern Lower Michigan, cross-sections of fire-killed red pines were analyzed to assess the historic intervals between understory fires in the jack pine forest with scattered red pines established in the 1820s . The Mack Lake Fire was a fast-moving (advanced 7.5 miles (12 km) in the first 3.5 hours), large (24,000 acres (9,700 ha)) fire that consumed 270,000 tons (240,000 t) of fuel. The fire burned 16% of the total red pine stands (3,707 acres (1,500 ha)) in the Mack Lake area . Prefire red pine ages ranged from approximately 69 to 162 years, and the earliest recorded fire in the study area was from 1839. Understory fire-return intervals for individual trees on the 8 sites ranged from 15.1 to 33.2 years, with a mean of 24.7 years. Individual trees had an average of 5.9 fire scars. Mean fire-return intervals across the 8 sites ranged from 15.4 to 31.0 years, with a mean of 18.9 years .
From 1696 to 1920 the mean fire-return interval in Algonquin Park, Ontario, where red pine is a minor component, was 70 years. The study site is dominated by eastern white pine and quaking aspen. Red pine is scattered throughout the park, but is not found in sizeable pure stands. Lightning is the major source of ignition for fires in the region. Fire exclusion began in the area in 1921 .
Red pine at the northern limit of its range: At the northern limit of its range, red pine is restricted to lake landscapes and rough topography [27,31,95]. Bergeron and Brisson  studied the frequency, extent, and severity of fires at the northern limit of red pine distribution on 2 islands in Lake Duparquet in northwest Quebec. From 1800 to 1986 there were 5 low-severity fires on a sand dune island site and 6 fires (3 low-severity, 3 high-severity) on a peninsular site (1814, 1881, 1892, 1906, 1930, and 1971), giving an average fire-return interval of 30 years (SD 18). The fire-return interval for understory fires was shorter, averaging 25.7 years . The extent of fires on both islands was highly variable. Most fires covered 25% to 50% of the sand dune island site. Because of the severity of the 1906 fire on the peninsular site, the extent of previous fires could not be estimated. Boreal forests to the north of red pine's northern limit have mostly crown fires; because large, stand-replacing fires eliminate the seed source, red pine's expansion northward is limited [31,95].
Red pine at the eastern limit of its range: Red pine is uncommon in New England, where it is restricted to small, isolated stands or mixed-conifer stands on lakeshores, rocky ridges, and sand plains. These red pine stands are small islands of fire-prone habitat surrounded by relatively nonflammable, deciduous forests . On Resin Ridge in northern Vermont, Engstrom and Mann  describe a mean interval for understory fires in red pine stands of 37.4 years, and a range of 3 to 102 years, for the period 1815 to 1987. Red pine stands at Resin Ridge occur on steep, south-facing slopes. The majority of fires on Resin Ridge were surface fires that neither killed mature trees nor stimulated red pine recruitment. High-severity fires promoting red pine seedling recruitment likely occurred at intervals of 50 to 100+ years between 1815 and 1987 .
In northern Vermont the fire ecology of 6 red pine populations along a 3-mile (5-km) ridge, best described as a foothill of the Green Mountains, was investigated for the period 1829 to 1987 . Red pine was found in small, pure clusters, and mixed with eastern white pine, red spruce, and eastern hemlock. Mature red pines on the ridge were characteristically small, averaging 8 to 10 inches (20-30 cm) DBH and 70 feet (20 m) tall. Between 1829 and 1987, 17 fires occurred on the ridge, 3 of which burned into at least 2 red pine stands (all within the same population). No fires had occurred since 1922. Following high-severity fires, regeneration pulses occurred in the 6 populations. While red pine was the dominant canopy species, it did not dominate the subcanopy, since fires had not occurred since 1922. The subcanopy was dominated by eastern white pine, red spruce, American beech, and red maple .
Red pine is the rarest conifer species in Newfoundland, with only 22 widely-dispersed locations containing 15,000 mature and semimature red pines. Beginning in 1977, Roberts and Mallik  sampled 8 locations to identify the age class structure and number of mature trees originating after known fires in Newfoundland. At site 1, in west-central Newfoundland, small fires were recorded in 1891, 1916, 1947, 1950, 1961, and 1977. At site 2, in central Newfoundland, most of the red pines originated from 1890 fires, though fires also occurred in 1899, 1904, and 1938. At site 3, in eastern Newfoundland, most trees originated from a 1904 fire, with fires also occurring in 1946 and 1979 .
|Age-classes and approximate % of mature trees in each age class for red pine stands originating after wildfires (as of 1985). Rowsells Brook and Grant's Pit are the largest stands with >3,000 trees .|
|Age class (years)||10-40||40-60||60-80||80-120||120-150||100-250|
|Stands within site 1|
|Stands within sites 2 and 3|
Effects of fire exclusion: As presented in research above [11,53,66,77,103,104,173], postsettlement fire exclusion from red pine stands has caused a decrease in nonlethal understory fires and a shift toward long return-interval, stand-replacement fires. Long periods between fires favor more shade-tolerant species [39,40,186].
The fire-return interval in many red pine forests has changed, leading to the decline and near or complete extirpation of red pine in those areas. In the pine barrens of northwestern Wisconsin, an increased fire-return interval reduced the cover of jack pine-red pine-eastern white pine communities by 368,000 acres (149,000 ha) from presettlement times to 1987. In turn, hardwood species increased by 376,000 acres (152,000 ha). Red pine has decreased in cover by 80%, and much of the red pine that does remain is on plantations that were historically occupied by jack pine. Areas historically covered with red pine are now dominated by quaking aspen due to a changing fire regime or overlogging .
According to Heinselman's 1981 analysis , fire exclusion in old-growth red pine stands in the Great Lakes-St Lawrence forests has created a "new fuels situation." In the Boundary Waters Canoe Area and Itasca State Park, Minnesota, many red pine stands bearing fire scars from previous fires have moderate to dense understories of balsam fir, white spruce, black spruce, and sometimes northern white-cedar. These conifers, which have branches nearly to the ground, have attained heights that bring their crowns in contact with the red pine canopy, creating fuel ladders that can carry fires into the overstory. While such understories also developed before fire exclusion, periodic low- to medium-severity fires reduced ladder fuels, so fire did not often reach the canopy. If fire exclusion continues, understory fuel layer buildup may cause fires of such intensity that the restoration of presettlement fuel conditions will be difficult .
Red pine is declining in the Boundary Waters Canoe Area due to fire exclusion. Scheller and others  predict that if fire exclusion continues, red pine will continue to dwindle. Using simulation models, the researchers predicted that if fire was reintroduced at intervals of 50 to 100 years, red pine would increase. A fire-return interval of 300 years, while not ideal, would increase production of red pine over current production .
Climate change and fire frequency/intensity: It is suggested that global climate change will increase both the frequency and intensity of forest fires. However, research conducted by Bergeron and Flannigan  found that the opposite may be true in the southeastern Canadian boreal forests. From the end of the "Little Ice Age" (approximately 1850-1989), surface temperatures have risen 5 °F to 7 °F (3-4 °C) in the Lake Duparquet region of Quebec. Yet fire frequency between 1870 and 1989 was 34% lower than in the preceding 74 years. In the southeastern boreal forests, global warming may cause a weakening of the upper trough over eastern Canada, shifting the polar front north. This would lead to higher relative humidity and more precipitation, causing a less severe fire regime than is currently present. Under this changing regime, red pine may increase if there is enough time between stand-replacing fires to red pine mature (20-40 years) and regenerate .
At Itasca State Park, Clark  analyzed the effect climate change has had on fire frequency over the last 750 years. The study site consists of an interrupted canopy of red pines and eastern white pines that are 100 to 110 feet (30-35 m) tall and 100 to 400 years old. Over the last 750 years, the fire-return interval (determined from fire scar and charcoal stratigraphy data) was shortest (8.6 years (SD 2.9)) during the warm and dry 15th and 16th centuries. Cooler, moister conditions from 1240 to 1440 increased the fire-return interval to 13.2 years (SD 8.0). The fire-return interval was further increased with the onset of the "Little Ice Age." During the mid-18th and mid-19th centuries, fire-return intervals averaged 24.5 (SD 10.4) and 43.6 (SD 15.9) years, respectively. Shortterm warm, dry periods within that time frame decreased the fire-return interval to 17.9 years (SD 10.6) from 1770 to 1820 and 12.7 years (SD 10.1) from 1870 to 1920. Fire exclusion in the study area began in 1910 and has reduced fires . Clark  suggests that had fire exclusion not been implemented, fire frequency would have increased 20% to 40% in the 20th century due to warmer, drier conditions.
The following table provides fire regime information that may be relevant to red pine.
|Fire regime information on vegetation communities in which red pine may occur. For each community, fire regime characteristics are taken from the LANDFIRE Rapid Assessment Vegetation Models . These vegetation models were developed by local experts using available literature, local data, and/or expert opinion as documented in the PDF file linked from the name of each Potential Natural Vegetation Group listed below. Cells are blank where information is not available in the Rapid Assessment Vegetation Model.|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires|| Mean interval
|Great Lakes Woodland|
|Great Lakes pine barrens||Replacement||8%||41||10||80|
|Surface or low||83%||4||1||20|
|Jack pine-open lands (frequent fire-return interval)||Replacement||83%||26||10||100|
|Northern oak savanna||Replacement||4%||110||50||500|
|Surface or low||87%||5||1||20|
|Great Lakes Forested|
|Northern hardwood maple-beech-eastern hemlock||Replacement||60%||>1,000|
|Conifer lowland (embedded in fire-prone system)||Replacement||45%||120||90||220|
|Conifer lowland (embedded in fire-resistant ecosystem)||Replacement||36%||540||220||>1,000|
|Great Lakes floodplain forest|
|Surface or low||93%||61|
|Great Lakes spruce-fir||Replacement||100%||85||50||200|
|Minnesota spruce-fir (adjacent to Lake Superior and Drift and Lake Plain)||Replacement||21%||300|
|Surface or low||79%||80|
|Great Lakes pine forest, jack pine||Replacement||67%||50|
|Surface or low||10%||333|
|Surface or low||67%||500|
|Maple-basswood mesic hardwood forest (Great Lakes)||Replacement||100%||>1,000||>1,000||>1,000|
|Surface or low||89%||35|
|Northern hardwood-eastern hemlock forest (Great Lakes)||Replacement||99%||>1,000|
|Surface or low||81%||85|
|Red pine-eastern white pine (frequent fire)||Replacement||38%||56|
|Surface or low||26%||84|
|Red pine-eastern white pine (less frequent fire)||Replacement||30%||166|
|Surface or low||23%||220|
|Great Lakes pine forest, eastern white pine-eastern hemlock (frequent fire)||Replacement||52%||260|
|Surface or low||35%||385|
|Eastern white pine-eastern hemlock||Replacement||54%||370|
|Surface or low||34%||588|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Eastern woodland mosaic||Replacement||2%||200||100||300|
|Surface or low||89%||4||1||7|
|Rocky outcrop pine (Northeast)||Replacement||16%||128|
|Surface or low||52%||40|
|Surface or low||65%||12|
|Oak-pine (eastern dry-xeric)||Replacement||4%||185|
|Surface or low||90%||8|
|Northern hardwoods (Northeast)||Replacement||39%||>1,000|
|Eastern white pine-northern hardwoods||Replacement||72%||475|
|Surface or low||28%||>1,000|
|Northern hardwoods-eastern hemlock||Replacement||50%||>1,000|
|Surface or low||50%||>1,000|
|Northeast spruce-fir forest||Replacement||100%||265||150||300|
|Vegetation Community (Potential Natural Vegetation Group)||Fire severity*||Fire regime characteristics|
|Percent of fires||Mean interval
|Southern Appalachians Woodland|
|Table Mountain-pitch pine||Replacement||5%||100|
|Surface or low||92%||5|
Replacement: Any fire that causes greater than 75% top removal of a vegetation-fuel type, resulting in general replacement of existing vegetation; may or may not cause a lethal effect on the plants.
Mixed: Any fire burning more than 5% of an area that does not qualify as a replacement, surface, or low-severity fire; includes mosaic and other fires that are intermediate in effects.
Surface or low: Any fire that causes less than 25% upper layer replacement and/or removal in a vegetation-fuel class but burns 5% or more of the area [118,161].
|Red pine stand 6 months after a prescribed fire. Photo courtesy of Scott Roberts, Mississippi State University, Bugwood.org.|
IMMEDIATE FIRE EFFECT ON PLANT:
Mature red pine (beginning at age 20 to 40) can survive low- to moderate-severity surface fires [4,15,27,46,56,57,72,94,134] due to thick, fire-resistant bark [4,46,51,94,95,125,126,141,147,288] that protects the tree's cambium . High-severity fires raise the risk of tree mortality via crown fires, crown scorch, cambial injury, and root mortality [4,15,29,72,94,134]. Red pine can, however, survive following "substantial" crown scorch [72,134,187,189,285], cambial injury [44,230,288], charring , and needle kill . Trees have a better chance of survival following crown scorch if scorch occurs before bud flush . Van Wagner's  prescribed fire studies red pine stands in eastern Canada showed that surface fires of less than 200 BTU/sec-ft rarely scorch the crown of red pine, a surface fire of 500 BTU/sec-ft is "on the edge of dangerous" for the largest red pines, and a surface fire of 1,000 BTU/sec-ft or more results in complete red pine mortality.
Red pine seedlings and saplings are more susceptible than mature trees to fire mortality [3,129,130] and heat damage (see Heat tolerance). Crown fires are much more likely in younger red pine stands, where crowns are closer to the ground . Red pine stands may support crown fires at 15 to 20 years of age [129,130]. However, Methven  found that red pine seedlings can survive following a high degree of needle scorch. There was little information (as of 2008) on the immediate effect of fire on the seeds and/or cones of red pine, though several researchers state that cones and seeds are "very susceptible" to fire mortality [4,129,130,230].DISCUSSION AND QUALIFICATION OF FIRE EFFECT:
Crown scorch: Mature red pines can survive substantial crown scorch . On 31 May and 15 June, Methven  carried out prescribed burns in 2 mature red pine stands to assess the effect of crown scorch. Red pines in stand 1 (May burn) ranged in diameter from 9 to 17 inches (20-43 cm), and trees in stand 2 (June burn) averaged 5 to 15 inches (10-38 cm). An "appreciable" amount of crown scorch occurred, particularly in stand 2, due to either ignition pattern or localized fuel concentrations. In June of the following year, mortality of red pine due to crown scorch was measured. Red pine mortality began with 46% to 50% crown scorch, reached 50% mortality with 81% to 85% scorch, and 100% mortality occurred with 96% to 100% crown scorch. The researcher did not distinguish the rate of mortality by diameter class, since 96% of the trees in the study had a DBH of 9 inches (20 cm) or greater . However, a previous study found higher mortality associated with crown scorch in trees with DBH less than 9 inches (20 cm) .
Van Wagner  conducted a series of prescribed burns in 80-year-old red pine-eastern white pine stands in eastern Ontario and found that red pine survived crown scorch and stem charring. The burn sites were on nearly level sand and gravel deposits along the Petawawa River. Fires were conducted on 3 plots (I-III) with 4 series (1-4) of burns on each plot. Plot II-1 and plot III-1 were burned in both 1959 and 1960 .
|Burning conditions and dates for prescribed burns in a red pine-eastern white pine community |
|Plot series||Date of fires||
Moisture content of fuels
Rate of spread
Wind speed near ground
|Top duff layer||Full duff layer||With wind||Against wind|
|1||24-25 June 1959||2.4||36||18||68||1.2||0.7|
|2||31 May 1960||1.9||53||19||41||1.1||0.8|
|3||10-11 August 1960||2.0||38||16||32||1.5||0.8|
|4||19 August 1960||2.7||30||10||14||4.7||1.2|
Headfire intensity (BTU/second/foot) of front and rate of spread (feet/minute) were measured on all sites except III-4, which was disturbed and could not be burned .
|Headfire intensity and rate of spread of 11 fires in a red pine-eastern white pine community |
|Plot/series||Headfire intensity of front (BTU/sec/ft)||Rate of spread (ft/min)|
One year following the fires, crown damage and pine mortality were evaluated. Damage to pines was negligible on burned sites with fireline intensity less than 41 BTU/sec./ft. Pine damage on the remaining plots was related to fireline intensity .
|Comparison of headfire intensity and damage to red and eastern white pines on the 4 plots burned with the highest severity |
|Plot/series||Headfire intensity of front (BTU/sec./ft.)||Average height of scorch line (feet)||Average % of crown scorch (pines 6 inches DBH or greater)||Average maximum stem height charred (feet)||Average minimum stem height charred (feet)|
|Crown damage and first-year mortality following the 1960 fires |
|Crown scorch (%)||Number of pines||% dead after 1 year|
|*Diameter range in the group was 2 to 12 inches (5-30 cm).|
Following a 12 April 1966 fire in a 47-year-old red pine plantation in Minnesota, tree survival was high even in trees with over 50% crown scorch .
|Effect of crown scorching on the survival of red pine after an April 1966 fire |
|Approximate percent of
|Percent of trees still alive on 5 dates|
|8 June 1966||9 July 1966||18 October 1966||20 June 1967||9 October 1967|
For further information on this study, see Seedling establishment following fire and the Research Project Summary of Van Wagner's  study.
Low-severity fires: In a red pine-eastern white pine plantation in Michigan's southwestern lower peninsula, Neumann and Dickmann  found that single (10 May 1991) and repeated (10 May 1991 and 10 May 1993) low-severity burning did not affect the red pine overstory. However, single and repeated burning caused a significant decrease in pine and hardwood saplings and large seedlings (P=0.05). Further, in 1994, pine seedlings were fewer on burned than unburned sites. For more information, see the Research Project Summary on this study.
Mortality following high-severity fires: In the following studies red pine mortality occurred following high-severity fires. In mid-May 1971 a high-severity fire burned almost 15,000 acres (6,100 ha) in the Boundary Waters Canoe Area. The fire completely scorched and killed many of the mature red pine and eastern white pine. The first summer after the fire no red pine or eastern white pine seedlings established, which is to be expected since seed shedding does not occur until fall. By the end of the summer, understory vegetation in the red pine-eastern white pine community was dominated by pin cherry (Prunus pensylvanica) .
A high-severity August 1995 fire on the southeast side of Quetico Provincial Park, Ontario, caused mortality of red pines . The crown fire swept through 200- to 300-year-old red pine stands with such intensity (up to 40,000 kW/m) that in places, the organic soil layer was totally consumed, exposing red pine roots. Tree mortality was near 100% on the ridges of high-severity burn sites, with surviving trees generally found near the edges of lakes or rivers . For further information on the study, see Seedling establishment following fire.
Root sensitivity to heat: While severe fires can cause root mortality [72,134], a single, low-severity prescribed fire did not cause red pine fine root mortality at the W. K. Kellogg Experimental Forest near Augusta, Michigan . The backfire was conducted during June in a stand of red pine approximately 50 years old and averaging 65 feet (19.8 m) tall. During the fire, temperatures reached at least 160 °F (73 °C) for about 12 minutes at the soil surface. At 0.8 inch (2 cm) and 2 inches (6 cm) below the soil surface, temperatures remained relatively constant at approximately 57 °F (14 °C) and 61 °F (16 °C), respectively, for 40 minutes. At the site, red pine fine roots to a depth of 4 inches (10 cm) represented 11.8% of the total forest floor root mass. The minimum temperature required to cause "substantial rapid root mortality" in red pine is 127 °F (52.5 °C), with temperatures of 140 °F (60 °C) or higher causing complete fine root mortality .
Seedling needle scorch: Red pine seedlings can survive substantial needle scorch . In an August laboratory experiment, 3-year-old red pine seedlings were subjected to temperatures starting at 77 °F (25 °C), increasing incrementally to 200 °F (100 °C), and returning to approximately 95 °F (35 °C). Maximum temperatures were attained within 2 minutes, with the complete cycle occurring in 4 minutes. Red pine needle-tip scorch first appeared at around 100 °F (50 °C). Needle scorch rose rapidly from 20% to 70% at 140 °F (60 °C). Following heat treatments, the red pine seedlings were planted outside and the effect of needle scorch was measured in June of the following year. Red pine seedlings with up to 90% needle scorch had mortality of 10% to 20%. Significant mortality did not happen until approximately 95% of the needles were scorched, which occurred at 180 °F (80 °C) .
Stem charring: Two wildfires (severity not described) in Newfoundland, 1 in the spring of 1997 (SL1) and the other in the summer of 1979 (Grant's Pit), caused substantially greater red pine mortality in mixed stands (25-50% black spruce and 50-75% red pine) than in pure red pine stands . Following the 2 fires, Roberts and Mallik  measured tree survival rates, stem char heights, and tree heights in pure and mixed stands on flat, downslope, and upslope positions. Survival was consistently low in mixed stands and consistently high in pure red pine stands. Average char height was not consistently related to survival. Relationship between slope position and survival was not clear .
Effects of a spring and summer wildfire on the structure of a pure red pine and mixed stand at 3 topographic locations 
SL1 (spring 1977 fire)
Grant's Pit (summer 1979 fire)
|Survival (%)||Stem char height
|Average tree height
|Survival (%)||Stem char height
|Average tree height
|Pure red pine stands|
|Flat||95||0.9a (SD 0.4)||11.4 (SD 1.3)||90||4.3a (SD 0.9)||15.8 (SD 1.2)|
|Downslope||90||1.3a (SD 0.5)||11.4 (SD 1.3)||90||8.6b (SD 2.1)||15.8 (SD 1.2)|
|Upslope||75||7.9b (SD 0.9)||11.4 (SD 1.3)||90||12.4c (SD 2.3)||15.8 (SD 1.2)|
|Flat||20||9.7a (SD 2.1)||11.4 (SD 1.3)||35||12.0a (SD 2.1)||15.8 (SD 1.2)|
|Downslope||20||7.4b (SD 0.9)||11.4 (SD 1.3)||35||11.5a (SD 2.1)||15.8 (SD 1.2)|
|Upslope||20||11.1c (SD 1.2)||11.4 (SD 1.3)||25||13.0a (SD 2.6)||15.8 (SD 1.2)|
|Mean char heights followed by different letters in the same column are significantly different (P<0.05)|
Fire not only promotes red pine seedling establishment, but can promote root/shoot growth in surviving trees  and an increase in resin flow [171,236]. Increased resin flow helps stop bark beetles and wood-decaying fungi from entering fire scars [11,236,294].DISCUSSION AND QUALIFICATION OF PLANT RESPONSE:
A late summer high-severity fire in Quetico Park, Ontario, burned 440 acres (180 ha) of forest, including a 5-acre (2-ha) stand of mature red pine. Approximately 50% of the red pine stand survived and provided seeds for eventual reestablishment. Seedling establishment, which was described as "abundant", began at about postfire year 6 when the ash layer was reduced on the shallow, sandy loam soil. The majority of red pine establishment occurred in 2 pulses roughly 7 years apart, which coincides with the usual interval between good seed crops .
|Average number of red pine seedlings, saplings, and seed-producing trees 13 and 19 years after fire at Quetico Park, Ontario |
|Years after fire||Seedlings/acre||Average age of seedlings (years)||Average seedling height (feet)||Saplings/acre||Seed-producing trees/acre|
More seedlings established on low-severity than high-severity summer burned sites in northwestern Ontario. The low-severity August 1995 fire at Kenny Lake occurred in a "poor" seed year, but resulted in red pine seedling establishment. "Most" red pines survived, but all balsam fir trees were killed at Kenny Lake. At the high-severity burn sites at Kawnipi Lake, there was almost complete tree mortality. Seedling establishment was evaluated in the first postfire year. Although 1995 was a described as a "poor" seed year, most red pines produced some cones .
Prefire live stems/ha and postfire seedlings/ha of red pine high-severity and low-severity burn sites at Quetico Provincial Park 
|Kawnipi Lake site 1||81||0|
|Kawnipi Lake site 2||121||375|
|Kawnipi Lake site 3||59||0|
|Kawnipi Lake site 4||37||125|
One full growing season after the fires conducted by Van Wagner , which are discussed more fully above, red pine and eastern white pine seedlings were counted on the burned sites (seedling counts were made 2 years after the fire on plot I-1). In general, pine seedlings were greatest on sites where high-severity fires occurred and lower where low-severity fires occurred. Sites that burned with the highest severity were I-3, I-4, II-3, and II-4. Van Wagner also measured the amount of soil bared by the fires .
Pine regeneration and soil bared following burning of 11 sites 
|Plot/series||Number of red and eastern white pine seedlings||Bared soil (%)|
|*Seedlings counted 2 years after fire in I-1 plot.|
Eight years following a prescribed fire in a Connecticut forest dominated by eastern white pine, black oak, white oak, and sweet birch, red pine stem density significantly increased due to seedling establishment (P<0.01) . The fire occurred during the final week of April 1985. Fine fuel moisture was 28% in the morning and decreased to 18% by afternoon. Rate of spread was slow (~1 m/min), and flame length was generally less than 10 inches (30 cm). Within the site, part was "lightly" burned with approximately 40% of tree density and 30% of tree basal area eliminated, while the other part was severely burned, reducing tree density 70% and basal area 60%. In postfire year 8, red pine stem density and frequency on both the control site and lightly burned site with an intact overstory was 0%, while stem density and frequency on the severely burned site without an overstory were 460 stems/ha and 19%, respectively .
Root/shoot growth: In the laboratory, red pine primary root and shoot growth was greater in heat-treated organic matter than in unheated organic matter . Red pine seed germination varied among treatments. Organic matter was heat-treated for 30 minutes prior to red pine seed plantings. Root and shoot measurements were taken 2 weeks following planting. As the organic matter was subjected to high temperatures, pH increased .
Seed germination and seedling growth of red pine in sand, unheated organic matter, and heated organic matter 
|Primary root||Primary shoot|
|Unheated organic matter||3.0||96||3.19||260.30|
|200 °C||slightly >3||80||10.31||224.35|
Resin: Fifty-five days following a surface fire on 8 May in a 44-year-old red pine forest near Colfax, Wisconsin, resin mass in red pines with scorched boles was more than double that in unscorched trees. Resin mass from boles of scorched trees was 0.68 g compared to 0.29 g from boles of unscorched trees . At Itasca State Park, old-growth red pines charred by a spring prescribed fire to a mean height of 15 feet (SD 11.5) (4.57 m, SD 3.51)), with a range of 1.1 to 37.86 feet (0.35-11.54 m), showed an increase in resin mass compared to unburned red pines. Among red pine burned, resin mass increased linearly with height of charring .FIRE MANAGEMENT CONSIDERATIONS:
Avian populations: Many bird species preferred burned over logged mixed conifer-deciduous forests in northeastern Minnesota. Schulte and Niemi  conducted bird censuses in early-successional burned (7% red pine cover) and logged forests (1% red pine cover) during breeding seasons, 2 and 3 years after fire. Time of logging was not provided; logged sites were selected to match the burned site. Overall bird species richness and density (territorial males/ha) were significantly higher in burned than logged forests (P<0.05) .
Bark beetles: Bark beetle attacks on red pines may increase following fire, though immediate mortality is rare. In a 44-year-old red pine stand, local burning of red pine boles caused a significant increase in bark beetle attacks (P=0.0044), but 6 years after treatments only 2 of the 58 experimental trees was killed. The trees, averaging 60 feet (SD 4.9) (18.3 m (SD 1.5)) tall, were located near Colfax, Wisconsin. They were burned with a propane torch on 23 June. Bark beetles (Ips pini and I. grandicollis)began to land on the burned area of the trees within the first week; highest landing rates were in the week following burning. Bark beetle attacks on burned red pines were more than double those on unburned trees, and attacks were almost always (79 of 86 attacks) within the scorched area of the tree. Most beetles failed to reproduce .
An April prescribed fire in an old-growth red pine stand in Itasca State Park caused a temporary increase in bark beetle infestations . Red pines were charred to a mean height of 15 feet (SD 11.5) (4.57 m (SD 3.51)), with a range of 1.1 to 37.86 feet (0.35-11.54 m). By 1 May, I. pini had increased two-fold over prefire levels but by the middle of July had returned to prefire levels. Bark beetle species I. grandicollis and I. perroti did not increase at any time following burning .
Changes in understory: Many studies are available on the effects of low-severity prescribed fires on red pine understory species where red pine was not affected by the fire(s) [41,42,43,67,190,191,198].
Duff consumption and moisture content: Prescribed fire can be used to prepare a mineral seedbed for red pine. Fires set when litter is moist may not be effective because duff consumption decreases as duff moisture content increases . A prescribed fire, set in a stand of red pine and eastern white pine in the Ottawa River Valley, illustrates how duff moisture content affects duff consumption. The fire had flame lengths of 1 to 4.9 feet (0.3-1.5 m) and a rate of spread of 1 to 10 feet (0.3-3 m)/minute. At approximately 20% moisture content, 2.8 kg/m² of duff was consumed. The rate of duff consumption steadily declined to 0.5 kg/m² of duff consumed at 80% moisture content, and 0% duff consumed at approximately 135% duff moisture content. The researcher also measured the percent of surface soil bared in relation to duff moisture content. At 20% moisture content, 30% of the surface was bared to mineral soil. About 5% of bared soil was at 60% moisture content .
At Petawawa Forest Experiment Station, Chalk River, Ontario, Van Wagner  sampled the dry weight and bulk density of the duff layer in a 35-year-old red pine forest with an average DBH of 5.8 inches (15 cm) from May to October during 1964 to 1967. The average duff dry weight was 0.85 lb/ft², with a range of 0.38 to 1.78 lb/ft². The average bulk density of the duff layer was 0.064 g/cc, with a range of 0.042 to 0.124 g/cc .
Litter: In red pine stands, needle litter accumulates at increasing rates until shortly after crown closure. At this point, accumulation levels off at values ranging from 11,000 to 16,000 lbs/acre [160,203]. Fuel loadings in northern Ontario red pine stands are approximately 5.3 tons/acre of woody surface fuel and 10.5 tons/acre of forest floor material (Stocks and others as cited in ). Fuels in red pine stands may "stabilize after several years", so fuel reduction may not be needed to prevent stand-replacement fires .
Brown  measured surface fuels in 9 red pine stands in National Forests of Michigan and Minnesota, ranging from 21 to 180 years old with basal areas/acre of 85 to 195 feet². The dry weight of surface fuels, consisting of needles (55%), branches (20%), and herbaceous and miscellaneous vegetation (25%), was highly variable. The average weight/acre was 5,600 lbs, with a range of 2,900 to 9,800 lbs. Dry weight of the total surface fuels (surface, litter, and duff) was also extremely variable, averaging 32,800 lbs/acre but ranging from 10,800 to 74,600 lbs/acre .
Following the May 1971 Little Sioux fire in northeastern Minnesota, total fall of litter and woody material measured for a 3-year period on a burned site exceeded that of an unburned site. The burn area was a mosaic of hardwood (quaking aspen, paper birch, red maple, and northern red oak), pine (red pine, eastern white pine, and jack pine), and spruce-fir (black spruce, white spruce, and balsam fir) stands. The prefire overstory basal area was 15.6 m²/ha; postfire measurements were not provided .
|Total litter and woody material fall (g/m²) during 3 postfire years in a mosaic forest of northeastern Minnesota |
*Values within the same column are significantly
different at the 0.05 level.
**Values within the same column are significantly different at the 0.01 level.
There is little variability in ash and silica-free ash content of dead red pine litter throughout the year. Red pine dead litter ash and silica-free ash content were measured at 2 sites in Lower Michigan during fall, spring, and early summer in 1973 and 1974. Ash content ranged from 2.1% to 3.0%, and silica-free ash content ranged from 1.6% to 2.3% .
Crown fuels: Brown  estimated crown fuel weights of uncut red pine stands of varying ages in the Huron-Manistee National Forest in Lower Michigan .
|Dry weight/acre of live and dead red pine crown material |
|Age (years)||Tree/acre||Needle weight (lbs)||Total crown weight (lbs)|
Moisture content of crown fuels: The moisture content is greater in new red pine needles (<1 year old) than in old needles (>2 years old). Measurements were taken from trees in Minnesota and Michigan throughout the 1962 and 1963 growing seasons. The moisture content of new needles declined throughout the growing season from a high of about 200% in late June to a low of 135% in October. Moisture content in old needles fluctuated (from 100-125%) throughout the growing season .
Van Wagner  measured the moisture content of new (current year's growth) and old (previous year's growth) red pine foliage from 1962 to 1965 in eastern Canada. The trees, growing on dry, sandy loam or dry sand, ranged from 20 to 40 years old and from 4 to 9 inches (10-20 cm) in diameter. The moisture content of new foliage reached a maximum of 270% in the middle of June and steadily declined to a low of 130% in October. Old foliage had a much lower moisture content, reaching a maximum of 110% in mid-March, declining to a low of 90% in early June, then increasing to approximately 107% by the end of October .
Flammability: Dense, pure red pine stands with trees less than 60 feet tall and a "clean" forest floor have higher potential for crown fire than stands of any other northeastern tree species [94,257]. Red pine stands are highly flammable until they reach about 60 feet (20 m) in height. Crown fire potential is less in stands taller than 60 feet (20 m) due to increasingly clear boles. Small crown fires in 50-foot-high (20 m) red pine plantations have energy outputs up to 6,500 BTU/sec-ft . Red pine stands have thick, loose needle litter. They produce more litter on more productive sites, but production may drop off and reach equilibrium soon after crown closure. While litter is produced faster on productive sites than on poorer ones, crown closure occurs faster on productive sites, thus shortening the period when fires are likely to crown. Young stands are very flammable due to a well-aerated litter layer [3,230]. As understory species establish in red pine stands, they create a layer of less flammable material [79,287].
Van Wagner  measured the heat of combustion of live red pine needles, freshly fallen leaf litter, and summer needle litter from trees in the Petawawa Forest Experiment Station, Ontario. The heat of combustion for the 3 samples was 5,216 (SE 40) cal/g, 5,327 (SE 22) cal/g, and 5,069 (SE 56) cal/g, respectively .
Growth: Based on tree ring data collected from red pines in central Newfoundland, red pine growth is generally depressed immediately following fires, but after approximately 4 years a surge in growth occurs that lasts for 4 or more years. After the initial red pine recovery period, increased growth is promoted by nutrient increases from the burned or charred organic material, removal of competing vegetation, and stand thinning .
Insect control with fire: Red pine cone beetles can cause extensive damage to red pine cones. Serious infestations of the beetle can lead to 20% to 100% cone mortality. In the Great Lakes States, red pine cone beetles overwintered on the ground in red pine buds that fell from approximately 22 October to 10 May. To assess the effect fire has on red pine cone beetles, Miller  conducted prescribed burns in Minnesota, Michigan, and Wisconsin during fall (8-10 November) and spring (29 April), when beetles were overwintering on the ground. Spring burning caused complete mortality of red pine cone beetles, with fall burning causing 95% mortality .
Leaf nutrient concentrations: Following a surface fire in Newfoundland, red pine needle nutrient content (nitrogen, phosphorus, and potassium) increased and maximum levels occurred 3 months after fire. Nutrient levels dropped "considerably" by postfire year 1 . Nutrient content of red pine needles before and 1 year after fire are provided by Roberts and Mallik .
Limnology: Following the 14 May 1971 Little Sioux Fire in northeastern Minnesota, Tarapchak and Wright  measured the effect that runoff from the burned forest (partially virgin red pine) had on Meander and Lamb Lake. For 2 years, beginning immediately after the fire, the researchers found no significant increases in lake levels of major ions, silica, total nitrogen, and phosphorus. Further effects of the Little Sioux Fire on the region's lakes are described in the article by Wright .
Logging: Logging followed by broadcast burning of red pine stands is generally unsuccessful in regenerating red pine stands if seed source is removed . In 1979, a pine-hardwood forest containing red pine (69 stems/ha and a basal area of 0.87 m²/ha) was clearcut and burned, eliminating red pine. By 1985, no red pine recruitment had occurred at the site, and future recruitment may require an outside seed source .
Plantations: Information pertaining to fire and red pine plantations is available from these sources: [73,74,133,134,291,309,317].Wildlife: Vogl  provides information on the benefits of burning red pine and other wildlife habitats in Wisconsin.
|Bald eagle perched atop a mature red pine, Seney National Wildlife Refuge, Michigan. Photo courtesy of Steven Katovich, USDA Forest Service, Bugwood.org.|
IMPORTANCE TO LIVESTOCK AND WILDLIFE:
While red pine is an important tree species for wildlife, but there is little in the literature describing its importance. The seeds are listed as a valuable food for wildlife , and Naylor  states that approximately 80% of the wildlife found in central Ontario use forests containing red pine and/or eastern white pine. In 2 reviews, however, red pine stands are described as poor habitat for game birds and animals [231,252].
Birds: Red pine stands can support a large variety of bird species. The Kirtland's warbler and the pine warbler are found exclusively in eastern white pine-jack pine-red pine stands, highly preferring jack pine stands over 80 acres (30 ha) in size [48,221]. Red pine and mixed stands with red pine provide habitat for numerous bird species in north-central and northeastern US forests [199,276,277]. Bald eagles and osprey nest in and colonies of great blue heron use red pines along waterways in central Ontario. Many other species of birds nest in red pines in central Ontario. See Naylor  for an extensive list of birds using red pine habitats.
Ungulates: Red pine is a low-preference food for white-tailed deer in Minnesota  and Massachusetts . In northeastern Minnesota, white-tailed deer browse red pine minimally in the winter. Most red pine browsed is blowndown trees and limbs . Red pine in northeastern Minnesota is a very minor moose dietary component, with the highest use occurring in the winter . During the dormant season in the Lake Superior region, moose show a "moderate" preference for red pine browse .
Small mammals: Red pine is a major food of snowshoe hares of Canada . Eastern white pine and red pine are the 2 most preferred conifer species for snowshoe hares. During the winters of 1958 to 1961, snowshoe hares on Manitoulin Island, Ontario, heavily browsed red pine bark and browsed red pine needles with medium to high intensity . Snowshoe hares also browse red pine seedlings in the winter and can damage seedlings. In Quebec, snowshoe hare damage to 3-year-old red pine seedlings was primarily incomplete stem girdling or complete browsing of terminal shoots, while some seedlings incurred severe browsing of the trunk or complete girdling of the stem below the lowest whorl of lateral branches .
In a mixed forest in northern Wisconsin, red squirrels abundantly consume red pine seeds. Red squirrels cache red pine cones in tunnels beneath middens not exceeding 3 feet (1 m) in diameter and 5.9 inches (15 cm) deep. Eastern gray squirrels also feed on red pine seeds in the area, but not with the abundance that red squirrels do . White-footed mice and meadow voles of the Northeast have a high preference for red pine seeds .
Palatability/nutritional value: At the time of this review (2008), there was only one article pertaining to the nutritional value of red pine foliage and no articles discussing the palatability of red pine. For foliar nutrient concentrations of mature red pines on the Cloquet Forestry Center, Minnesota, see Comerford and White .
Cover value: Red pine is an important cover species for a variety of bird species and other wildlife [22,231,252]. It is a prime nesting tree for bald eagles. On the Chippewa National Forest, Minnesota, 78% of bald eagle nests occur in red pines or eastern white pines. Bald eagles almost always nest in live trees. They position their nest below the crown at a main branch. Ospreys also nest in red pine and eastern white pines at Chippewa, but with less frequency (18%). Ospreys build their nests at the top of the tree . Bald eagles also nest in red pine on the Superior National Forest, Minnesota, but prefer eastern white pine . Bird species listed in the literature as using red pine for cover include prairie sharp-tailed grouse in the pine barrens of Wisconsin  and in northeast and north-central Minnesota , barred owls in north-central Minnesota , and ruffed grouse in Minnesota .
Downed red pine and red pine cavities are used as cover for a large variety of mammals in central Ontario . Red and eastern gray squirrels use red pine stands for cover in mixed forests of northern Wisconsin . Red pine, black spruce, jack pine, and eastern white pine are favored nesting trees for red squirrels in the Boundary Waters Canoe Area . Snowshoe hares are prevalent in red pine communities in north-central Minnesota . Gray wolves travel through and live within red pine and mixed forest stands on the Superior National Forest . Bats in Manistee National Forest, Michigan, use red pine as cover to hunt for flies, moths, and caddis flies .VALUE FOR REHABILITATION OF DISTURBED SITES:
Seed storage: Red pine seeds can be stored for up to 30 years if kept in a dry, sealed container at temperatures of 30 to 40 °F (1-3 °C) .OTHER USES:
Wood products: Red pine is a very important source of wood products [14,80,88,89]. It is used for lumber, pilings, poles, cabin logs, railway ties, posts, mine timbers, box boards, pulpwood, and fuel [22,89,231,252]. For more information on red pine and its importance in the wood industry, see the following articles: [22,85,88,89,99,205,231,252,253]
Fire-killed red pine: Basham  examines the deterioration of red pine by fungi following fire mortality in the Mississagi-Chapleau area of Ontario. Studies have also found that fire-killed, merchantable red pine is susceptible to beetle attacks .OTHER MANAGEMENT CONSIDERATIONS:
Browsing: White-tailed deer browsing can decrease red pine cover. White-tailed deer exclusion from a 230-year-old red pine forest promoted establishment and growth of red pine saplings in Itasca State Park. In 1937, white-tailed deer were excluded from a severely overbrowsed red pine site. At the time, white-tailed deer numbers were at or above starvation levels, and virtually no red pine saplings (or saplings of any other tree species) were present. By 1948, 84 red pine saplings ranging from 0.49 to 6.9 feet (0.15-2.1 m) high occurred in the 2-acre (1-ha) plot, while 0 saplings existed outside the enclosure. Beginning in the late 1940s, white-tailed deer were virtually eliminated from the Park due to hunting, so red pine saplings recovered outside of the exclosure. By 1957, there were 99 saplings inside and 309 outside the exclosure ranging from 0.49 to 6.9 feet (0.15-2.1 m) tall .
Disease: Red pine is relatively free of disease problems. Diseases that most commonly infect red pine are Fomes root rot , Scleroderris canker , and shoestring root rot .
Herbicides: There are several articles on the effects of herbicides on red pine. Sasaki and Kozlowski  studied the effects of 8 common herbicides on red pine seed germination and early seedling development. The effects of 11 different herbicides on red pine seed germination is reviewed by Baskin and Baskin . Noste and Phipps  and McCormack  provide information on the effects herbicides meant to control weeds have on red pine.
Host species: Red pine is rarely a host to eastern dwarf mistletoe (Arceuthobium pusillum) .
Insects: Red pine is exploited by over 200 insect species. Insect diversity is less than 50 species for most pine species . The most serious insect damage to red pine is to seed production during the second year of cone development . Insects that most commonly attack and damage red pine are the pine root collar weevil , pine shoot beetle , European pine shoot moth , jack pine budworm , red pine cone beetle [193,252], and white pine weevil .
Studies in Michigan indicate that bark beetles produced little red pine damage to unburned trees and did not select slower-growing trees. In Itasca State Park, infested red pines showed no evidence of declining growth when compared uninfested trees in the years preceding infestations. In Lower Michigan, the pine shoot beetle causes minimal damage to red pine shoots. Damage caused by the pine shoot beetle at 2 sites (northern Lower Michigan and southwestern Lower Michigan) from 1997 to 1999 ranged from 0.82 to 1.18 red pine shoots/m² in the north to 0.21 to 0.70 red pine shoots/m² in the southwest, where the pine shoot beetle is less established .
Needle droop: Red pine, particularly planted stock, is susceptible to needle droop. This occurs if sudden and excessive rapid transpiration occurs when there is limited soil moisture. Succulent tissues in the needle base collapse, which causes the needles to droop. Needle droop can cause mortality or deformation to large numbers of red pine seedlings .
Pest management: A pest management (insects, disease, and abiotic factors) analysis in red pine forests of Wisconsin is available from Schmoldt .
Red pine plantations: There is a plethora of information pertaining to red pine plantations. Topics include growth and development [35,211,219,300,311,312], stocking rates [211,219], fertilization [8,108], thinning and harvesting [21,63,88], establishing a plantation , site quality , growth with other species , and insect/fungal infestations [84,153].
Salt tolerance: Red pine seedlings have limited tolerance to sodium chloride spray .Wildlife management: Guidelines for managing wildlife habitat in red pine and eastern white pine forests of central Ontario are available .
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