The following annotated bibliography is an outgrowth of our concerns regarding the threat that intensive, heavily mechanized forest practices pose for the present and long-term health of Maine's forest ecosystems. Although industrial foresters claim to be practicing "scientific forestry", our review of the scientific literature in forest ecology shows that many of their practices such as whole-tree clearcutting on short rotations, herbicide spraying and creation of even-aged single-species tree plantations, have adverse effects on forest soils, on watersheds, and on the many diverse species of life which comprise a natural forest ecosystem. If we are to have healthy forests which are capable of providing high quality forest products, as well as wildlife habitat, watershed protection, and recreational opportunities, we must prevent the sorts of forest practices that maximize short-term profits for the multinational corporations at the expense of the long-term health of the forest.
We are private citizens and volunteers in this effort, not professional activists. This bibliography is not complete, but we intend to expand and update this survey as our time permits, and as new research results become available.
LeRoy Bandy, Jr., Ph.D. Wildlife Ecology. Barbara Bandy, M.S., Botany. 165 Stillwater Avenue, Orono, ME 04473.
Lorimer, C. G. 1977. The presettlement forest and natural disturbance cycle of northeastern Maine. Ecology 58:139-148.
Lorimer analyzed land survey records that covered over 4 million acres of Maine for the period 1793-1827. From these records he was able to determine that the average recurrence interval for fire for a given site would have been 800 years. Large-scale windthrows were even more infrequent, occurring every 1,150 years for a given site. Thus the forests of Maine prior to European settlement were not subject to frequent large scale disturbances, although that misconception continues to be spread by those who want to promote clearcutting as a form of harvesting that mimics natural disturbance.
Harmon, M., Ferrell, W. K. and Franklin, J. F. 1990. Effects on carbon storage of conversion of old-growth forests to young forests. Science 247:699-702.
The authors prepared a detailed analysis of the disposition of carbon resulting from the cutting of old-growth timber, and computer simulation models comparing carbon storage in an old-growth and a young forest. Their analyses demonstrate unequivocally that conversion of old-growth forests to younger forests has resulted and will continue to result in a net addition of CO2 to the atmosphere. Unfortunately, the misconception that cutting old forests and replacing them with young trees will reduce atmospheric carbon dioxide continues to be circulated by the misinformed.
Bergeron, Y. and Harvey, B. 1997. Basing silviculture on natural ecosystem dynamics: an approach applied to the southern boreal mixedwood forest of Quebec. Forest Ecology and Management 92:235-242.
The authors advance the idea that an understanding of natural ecosystem dynamics should form the basis for silvicultural practices in order to maintain biodiversity and long-term productivity. For example, they point out that successive rotations of conifers on the same site is not typical in the natural system and could cause nutrient depletion and decreased yields in the long term. They also cite evidence that mixed hardwood and softwood stands are preferable to stands managed for predominantly softwoods, since mixed stands contribute to ecosystem diversity and display important characteristics such as decreased susceptibility to spruce budworm outbreaks.
Fahrig, L. 1997. Relative effects of habitat loss and fragmentation on population extinction. Journal of Wildlife Management 61(3):603-610.
The goal of this simulation study was to assess the relative importance of habitat loss versus fragmentation on population extinction. Since habitat loss and fragmentation typically occur together, it is generally not clear which process has a greater effect on the extinction of species from an area. If fragmentation is the major problem, it should be possible to minimize the adverse effects of fragmentation by carefully arranging the pattern of forest disturbance on the landscape. For example, some biologists have advocated the clustering of clearcuts in certain areas,while other large areas are left undisturbed for long periods of time. The results of this study, however, indicate that total habitat loss is far more important than fragmentation in causing extinction. Therefore, the particular arrangement of clearcut areas on the landscape will not offset the adverse effects of forest habitat loss. In order to promote the survival of as many species as possible, habitat loss must be stopped, and habitat restoration pursued. Forest management methods should emphasize low-impact harvesting techniqes and the maintenance, as much as possible, of the structure and the function of natural forests.
Harvey, B. D. and Bergeron, Y. 1989. Site patterns of natural regeneration following clear-cutting in northwestern Quebec. Canadian Journal of Forest Research 19:1458-1469.
The authors compared pre- and post-harvest data on regeneration in balsam fir-white birch-spruce forest in northwestern Quebec. Results revealed severe softwood seedling mortality after whole-tree clearcutting, especially on certain types of clay soils. This research may have relevance for the Maine woods where the spruce-fir component of the forest (especially red spruce) has declined significantly since 1982.
McGee, G. G. and Birmingham, J. P. 1997. Decaying logs as germination sites in northern hardwood forests. Journal of Applied Forestry 14(4):178-182.
The authors studied the effects of downed decayed logs on the density of seedlings of seven tree species in a northern hardwood old-growth forest and in a mature (95 year old) second-growth stand. They found that yellow birch seedling densities were 24 times greater, and red spruce seedling densities were 5 times greater on decayed logs than on the forest floor. Highly-valued red spruce is in serious decline in Maine. Clearcutting and whole-tree harvesting on short rotations do not leave decayed "nurse logs" that could provide optimum habitat for regrowth of these species.
Federer, C. A., Hornbeck, J. W., Tritton, L. M., Martin, C., Pierce, R. S. and Smith, C. T. 1989. Long-term depletion of calcium and other nutrients in eastern U.S forests. Environmental Management 13(5):593-601.
The authors analyzed data on total nutrient loss from forest soils when whole-tree clearcutting was used as the harvest method. The data they used were taken from a number of published research studies conducted on six different forest sites in the eastern U. S., including sites in Maine and New Hampshire. The authors concluded that the essential element calcium, in particular, is in danger of being depleted from forest soils due to the combined effects of acid rain and intensive forest harvesting. For example, they predicted that the combination of leaching loss from soil and whole-tree harvests on 40-year rotations could deplete 50% of the total soil and biomass calcium in only 120 years. They also pointed out that calcium in a form readily available for plant use could be depleted even faster than total calcium. Their analysis showed that magnesium and potassium are also in danger of depletion.
Dahlgren, R. A. and Driscoll, C. T. 1994. The effects of whole- tree clearcutting on soil processes at the Hubbard Brook Experimental Forest, New Hampshire, USA. Plant and Soil 158:239-262.
The results of this study showed that whole-tree clearcutting of a northern mixed hardwood and spruce-fir forest created a severe ecosystem disturbance leading to increased acidification of the soil solution and streamwaters draining the clearcut site. Clearcutting resulted in the loss of the nutrient ions calcium, magnesium, potassium and nitrate from the forest soil into adjacent streams. In addition, potentially toxic (to fish and other aquatic organisms) levels of aluminum ions were released into the soil solution and streamwaters. These effects on water chemistry persisted for 3-4 years after the harvest.
Simard, S. W., Perry, D. A., Jones, M. D., Myrold, D. D., Durall, D. M. and Molina, R. 1997. Net transfer of carbon between ectomycorrhizal tree species in the field. Nature 388: 579-582.
Mycorrhizal fungi in the forest soil form beneficial associations with the roots of trees and enhance tree growth in various ways. It has been known for some time that these fungi can form networks bewteen the roots of different trees, even between trees of different species. Recently these researchers in British Columbia made an important breakthrough in understanding the ecological significance of these fungal-tree communities. They showed that seedlings of Douglas fir grown in the shade of paper birch received a net transfer of carbon from the birch trees through the fungal connections. This research shows that in a natural forest ecosystem, trees such as paper birch (considered a "weed"species by foresters) may nourish other tree species such as the commercially valuable Douglas fir. These complex interactions may help stabilize the forest ecosystem in the long run and help protect against extremes of moisture, temperature, and against insect outbreaks and disease. Unfortunately, intensive forest management techniques such as clearcutting and herbicide spraying disrupt these complex and beneficial associations between trees and fungi (e.g., see Zhou et al., 1997).
Zhou, M., Sharik, T. L., Jurgensen, M. F. and Richter, D. L. 1997. Ectomycorrhizal colonization of Quecus rubra seedlings in esponse to vegetation removals in oak and pine stands. Forest Ecology and Management 93:91-99.
Northern red oak is a commercially valuable species in the Lake States, but it is difficult to regenerate in that region. Studies have shown that seedlings of red oak perform better when grown in association with mycorrhizal fungi. The purpose of this study was to determine how different levels of harvesting intensity affected the naturally-occurring mycorrhizae in the forest soil. The results of this study showed that oak seedlings grown in soil from which the previous stand of trees had been harvested by clearcutting formed significantly fewer associations with mycorrhizal fungi. In contrast, oak seedlings grown in soil from areas harvested by partial cuts formed abundant associations with mycorrhizal fungi. The authors pointed out that their results agreed with a number of other previous reports showing that clearcutting reduces mycorrhizal populations and mycorrhizal root formation. The authors hypothesized that the higher soil temperatures found in clearcuts may have adversely affected the mycorrhizal populations.
Bird, G. A. and Chartarpaul, L. 1986. Effect of whole-tree and conventional forest harvest on soil microarthropods. Canadian Journal of Zoology 64:1986-1993.
Many small animals in the forest soil play important roles in the decomposition of organic matter and nutrient cycling. As they feed on dead organic matter and soil microorganisms, they contribute to soil fertility and improve soil porosity. Tiny insects and mites (microarthropods) are among the typical small animals found in forest soil. The researchers in this study found that whole-tree clearcutting resulted in a significant decrease in the number of soil microarthropods when compared to less intensive harvests in which not all trees were cut and the tops of cut trees were left on the ground. The authors hypothesized that a decrease in food supply (organic matter) and soil moisture as well as extreme temperature conditions on the whole-tree clearcut sites may have caused the decline in numbers of microarthropods.
Muller, R.N. and Bormann, F. H. 1976. Role of Erythronium americanum Ker. in energy flow and nutrient dynamics of a northern hardwood forest ecosystem. Science 193:1126 - 1128.
The trout lily (Erythronium americanum) is a widespread forest vernal herb which grows actively during the period extending from snowmelt until the forest canopy develops and shades the forest floor. The authors of this study found that these small plants incorporate significant amounts of potassium and nitrogen into their tissues during their period of active growth in early spring. If these plants were not present, those nutrients might be lost by leaching from the forest soil during snowmelt and spring runoff. Later in midsummer, the aboveground portions of the trout lily die back and release those nutrients into the soil from which they can be taken up by trees and other plant life. This study provides one example of how non-timber plant species may play important roles in the functioning of the total forest ecosystem.
Duffy, D. C. and Meier, A. J. 1992. Do Appalachian herbaceous understories ever recover from clearcutting? Conservation Biology 6(2):196-201.
Many herbaceous forest understory plants recover very slowly from major disturbances such as clearcutting. The authors of this study measured the extent of herbaceous cover and species richness in the understories of nine secondary forests which had been clearcut 45 to 87 years earlier. Cover and species richness were also measured in nine primary, or old-growth, forests and used for comparative purposes. The results indicated that the secondary forests failed to regain the same level of herbaceous cover and species richness that existed prior to clearcutting. Three possible explanations were given for these observations:
1) Recovery is so slow or variable among sites that 87 years post-harvest is insufficient time for reestablishment of herbaceous understory plants.
2) Such forests may never recover to match the herbaceous vegetation of the primary forest because climatic conditions may be different today than when the forests became established.
3) Herbaceous plants colonize pit and mound microtopography caused by the death of mature trees. Recovery therefore must await the growth, death and decomposition of the trees of the secondary forest.
The authors concluded that the herbaceous communities are unlikely to recover within the present planned logging cycle of 40 to 150 years, suggesting a continuing loss of diversity of undersory herbaceous plants.
To our knowledge a similar study has not been undertaken in Maine or in northern New England. However, the widespread use of intensive harvesting methods, short rotations and plantation forestry almost ensure a similar loss of regional herbaceous plant diversity.
Petranka, J. W., Eldridge, M. E. and Haley, K. E. 1993. Effects of timber harvesting on southern Appalachian salamanders. Conservation Biology 7(2):363-370.
In the forests of the eastern U.S., salamanders are often the most prominent group of vertebrates in both numbers and biomass. They are important members of forest food webs where they feed upon small invertebrates, and in turn, serve as a food source for a variety of larger predators. Unfortunately, in spite of their importance, salamanders are often neglected in forest management studies. In this study in western North Carolina, the authors compared species richness and abundance of salamanders on 6 recent clearcuts (< 10 years old) with that of 34 mature forest stands (> 50 years old). They found that densities of salamanders in mature forest stands were about 5 times greater than those on recent clearcuts. Also, the clearcut areas averaged only about half as many species as did the mature forest sites. The study indicated that 50 to 70 years are required for salamander populations to return to predisturbance levels. The authors estimated that approximately 70 to 80 percent of salamanders inhabiting mature stands are lost following clearcutting, and most of those probably die due to physiological stress. The authors cited other research which has shown that clearcutting disrupts the habitat for salamanders by removing shade, reducing leaf litter, and causing dramatic changes in soil surface moisture and temperature. The authors estimated that nearly 14 million salamanders were lost annually to clearcutting in national forests in western North Carolina.
Su, Q., MacLean, D. A., and Needham, T. D. 1996. The influence of hardwood content on balsam fir defoliation by spruce budworm. Canadian Journal of Forest Research 26:1620-1628.
This study was undertaken in northern New Brunswick to investigate the relationship between stand hardwood content and susceptibility of balsam fir to spruce budworm defoliation. Balsam fir stands with less than 40% hardwood content sustained 58 to 71% defoliation on average, versus 12 to 32% defoliation in stands with greater than 40% hardwood content. The results indicate that mixed balsam fir-hardwood stand management with a hardwood content greater than 40% could substantially reduce losses during spruce budworm outbreaks. The authors hypothesized that the presence of greater hardwood content increased the diversity and/or populations of natural enemies of the budworm such as birds. These results argue strongly for management strategies which promote greater forest community diversity, and against the establishment of monocultures and use of herbicides.
Crawford, H. S., and Jennings, D. T. 1989. Predation by birds on spruce budworm Choristoneura fumiferana: Functional, numerical, and total responses. Ecology 70(1):152-163.
The spruce budworm is a natural component in the spruce-fir ecosystem of eastern North America. The budworm's population follows a cyclical pattern oscillating between high and low densities at periods of approximately 35 years. Today, extensive clearcutting, heavy partial cuts, and herbicide use to minimize hardwood competition, have created dense stands of spruce and fir (mostly fir - the preferred budworm food). Such low diversity softwood stands will produce ideal conditions for future spruce budworm outbreaks. Past attempts to control the budworm by aerial spraying of insecticides have created unacceptable environmental problems and have possibly even extended the duration of budworm outbreaks.
The authors of this study investigated the hypothesis that predation by forest birds can dampen the rapid expansion of low-density budworm populations and thereby avoid severe infestations. By measuring breeding bird populations, bird feeding habits and rates of feeding, and budworm population levels, the authors were able to confirm that birds do exert controls on low-density budworm populations. The largest and most important group of predators was the canopy-feeding wood warblers (Blackburnian, Cape May, Bay-breasted, Yellow-rumped, Magnolia and Black-throated Green Warblers) as well as the Golden-crowned Kinglet. Such control was possible only when budworm populations were at low densities. Once a certain budworm threshold level was exceeded, avian control was lost. Furthermore, suitable habitat to ensure the presence of songbird populations which are capable of regulating sub-threshold budworm must be provided. A significant hardwood component and well-developed canopy and subcanopy layers are important habitat features. Forest practices which are common to Maine's industrial forestland, however, destroy those same habitat features which are necessary to maintain the essential canopy-inhabiting avian predators. The authors recommend silvicultural methods which will retain songbird habitat while allowing for prudent timber harvesting.
France, R. 1997. Land-water linkage: Influence of riparian deforestation on lake thermocline depth and possible consequences for cold stenotherms. Canadian Journal of Fisheries and Aquatic Science 54:1299-1305.
This study was undertaken to determine if riparian deforestation would expose lake surfaces to stronger than normal winds and thereby induce greater mixing of the water column. Such abnormal mixing could result in the intrusion of warmer surface waters into the colder bottom layer, the preferred summer habitat of the lake trout. Juvenile lake trout are known to segregate into the lower levels of the deepest portions of a lake to avoid interaction with adults. Compression of available habitat by riparian deforestation increases competition and potential cannibalism. Thus the well-being of a lake trout population could be adversely affected by decreased recruitment of younger age classes.
Sixty-three northwestern Ontario lakes around which riparian trees had been removed a decade before either through clearcutting or wildfire had warm surface layers which were over 2 m deeper per unit of fetch length when compared with lakes surrounded by intact riparian zones. The lake trout populations in those lakes were potentially at risk.
Maine law currently requires that 76 m (250 ft) riparian zones be established around ponds and lakes. However, 40% of the trees can be legally removed within the outer 50 ft of the zone; patch cuts (small clearcuts) are also allowed within the first 61 m (200 ft) of the riparian zone. The question arises, are Maine's riparian zones and associated timber harvesting regulations adequate to prevent lake fisheries habitat loss through the disruption of the normal lake stratification process?
Hagan, J. M., McKinley, P. S., Meehan, A. J. and Grove, S. L. 1997. Diversity and abundance of landbirds in a northeastern industrial forest. Journal of Wildlife Management 61(3):718-735.
This research, which was supported in part by the forest products industry, has been cited frequently by representatives of the paper industry as evidence that Neotropical songbirds benefit from industrial clearcuts. Actually, a careful reading of this paper shows that such a sweeping conclusion is not warranted.
First, it is important to note that this study was not conducted on typical industrial clearcut areas. The regenerating clearcut areas had not been sprayed with herbicides, as is common practice on industrial lands. Second, data on relative abundance of birds, such as that collected for this study, do not necessarily indicate successful breeding and reproduction (See Hagan et al., 1996. Conservation Biology 10 : 188 - 202). Furthermore, the results of this study do not bode well for those species of birds which require mature forests. In the authors' own words as quoted from this paper, " Over the coming decades, if harvest rates are maintained at current levels, bird (and other) species likely to decline in abundance will be species that prefer mature-forest habitats or large tracts of continuous mature forest coverage."
Hagan, J. M., Vander Haegen, W. M. and McKinley, P.S. 1996. The early development of forest fragmentation effects on birds. Conservation Biology 10(1):188-202.
The authors documented the early impact of clearcut harvesting and forest fragmentation on 5 species of forest-interior Neotropical songbirds in northwestern Maine. The sudden loss of habitat on clearcut sites forced breeding birds to disperse into adjoining forest fragments where they attempted to re-establish breeding territories. Overall songbird densities were observed to increase above normal levels due to the crowding of birds into the forest fragments. For Ovenbirds, crowding resulted in decreased mating success. Both density and reproductive success data were provided only for the Ovenbird; density data alone was provided for all other songbird species reported in the study. Had data on low mating success been omitted for the Ovenbird and had its status been based on density data alone, the species' well-being in forest fragments would have been inaccurately reported.
Darveau, M., Beauchesne, P., Belanger, L., Huot, J. and Larue, P. 1995. Riparian forest strips as habitat for breeding birds in boreal forest. Journal of Wildlife Management 59(1): 67-78.
The authors studied breeding bird abundance and species composition in experimental riparian strips adjacent to clearcut stands of balsam fir in Quebec's Laurentian Mountains. Densities of forest dwelling bird species suddenly increased 30 to 70% in the riparian strips in the year after cutting and decreased during the following 2 years to approximately pre-treatment levels. The authors suggested that the short-term crowding phenomenon was precipitated by the dispersal of nesting individuals from clearcut areas into remnant vegetation created by the riparian strips. Although reproductive success was not measured, the authors hypothesized that the high densities of forest-dwelling birds failed to reproduce successfully in the forest remnants because of crowding and that most birds ultimately perished. High songbird densities in remnant forest fragments do not necessarily indicate high quality habitat (See Hagan et al., 1996. Conservation Biology 10:188 -202 ).
Rail, J.F., Darveau, M. and Huot, J. 1997. Territorial responses of boreal forest birds to habitat gaps. Condor 99:976-980.
Treeless gaps resulting from intensive forest harvesting operations represent another aspect of the forest fragmentation and habitat loss phenomenon. Such gaps have the potential to adversely affect the productivity of forest songbirds through the disruption of behavior associated with territorial defense. To test this hypothesis, research was undertaken in boreal forest located 60 km to the north of Quebec City.
Playbacks of tape-recorded species-specific songs were used to determine whether boreal birds will cross treeless gaps to respond to territorial intruders. Treeless gaps of various types were used : clearcuts (12 - 100 m wide), unpaved roads (4 - 35 m wide ), unpaved roads with clearcuts on one or both sides ( mostly between 18 - 65 m wide ), powerline right-of-ways ( between 38 -55, 70 - 80 m, or 84 - 100 m in width), and cross-country skiing or pedestrian trails ( 3 - 15 m wide ). Forest interior species including Swainson's Thrush, Golden-crowned Kinglet and Black-throated-Green Warbler displayed a decreased probability of crossing 25 -40 m gaps. In continuous forest control plots these same three species displayed no reluctance to traverse distances up to 100 m to respond to playbacks. The White-throated Sparrow and Dark-eyed Junco, habitat generalists, displayed less reluctance to cross treeless gaps. Gap type had no effect on the probability of responding to playbacks.
Germaine, S. S. and Vessey, S. H. 1997. Effects of small forest openings on the breeding bird community in a Vermont hardwood forest. Condor 99:708-718.
The authors examined the response of a forest bird community to the presence of small openings that were created by patch clearcutting 0.4 hectare (1.0 acre) plots within extensive northern hardwood forest. Thirty-five (70%) of the 50 bird species encountered during censusing were Neotropical migrants. The presence of small openings in the mature hardwood forest raised the overall community diversity through the addition of habitat for several songbird species which require young tree or shrub growth. Many of these species were Neotropical migrants. The creation of small openings which mimic natural forest gaps offers a promising method by which to maintain regional Neotropical migrant bird diversity without resorting to large clearcuts.
Vander Haegen, W. M. and DeGraaf, R. 1996. Predation on artificial nests in forested riparian buffer strips. Journal of Wildlife Management 60(3):542-550.
Artificial nests were used to examine songbird nest predation in riparian buffer strips created by commercial clearcut harvests in the Narraguagus and Machias River watersheds in eastern Maine. Riparian zones in unharvested forest tracts were used as controls. Nests in riparian buffer strips were depredated more often than those in intact riparian forests. Nests in control stands experienced a 15% rate of predation, whereas nests located in 20 - 40 m wide buffer strips along tributary streams experienced a predation rate of 31%. Nests located in 60 - 80 m wide buffer strips along mainstem streams experienced 23% depredation. The narrow linear nature of the forest stands composing the buffer strips contributed to the elevated number and diversity of nest predators. Red squirrels and Blue Jays were responsible for > 50% of the nest predation. The authors recommended that forest managers leave buffer strips of 150 m (492 ft) or greater in width in order to reduce nest predation.
The primary function of riparian buffer strips is to lessen the impact of intensive timber harvesting on aquatic systems through the reduction of siltation and nutrient run-off and by the stabilization of water temperatures. As a secondary function, riparian buffer strips have been promoted as habitat and movement corridors for forest birds, mammals and other vertebrates. The latter function originated from research in the southwestern United States and was later extrapolated essentially untested to other regions of North America. In the northeast, the value of the riparian buffer strip as habitat and movement corridors remains controversial. In any case, less-intensive, low-impact forest management strategies which preserve a functional forest would make wildlife corridors unnecessary.
Parker, G. R., Kimball, D.G. and Dalzell, B. 1994. Bird communities breeding in selected spruce and pine plantations in New Brunswick. The Canadian Field Naturalist 108(1):1-9.
The authors surveyed breeding bird populations on 16 selected forest habitats in New Brunswick. Habitat types included natural spruce-fir forest, spruce and pine plantations, and natural post-harvest regeneration. In New Brunswick clearcutting is the most commonly used method of harvesting timber on large-scale areas in mixed and conifer-dominated forests. The density and diversity of breeding birds increased with the age of the stand since harvesting. Species richness, density and diversity of bird populations were correlated with the density and heterogeneity of conifer and deciduous stems >1 m tall. Clearcutting, intensive silviculture and single-species forest management were found to reduce habitat diversity and to decrease the density and diversity of breeding birds.
Krusic, R. A., Yamasaki, M., Neefus, C. D. and Perkins, P. J. 1996. Bat habitat use in White Mountain National Forest. Journal of Wildlife Management 60(3):625-631.
This study was undertaken to identify the bat species inhabiting the White Mountain National Forest (north-central New Hampshire and southwestern Maine) and to determine the pattern of habitat use displayed by those species. Six species were found to be present: little-brown bat, northern long-eared bat, small-footed bat, Indiana bat, big-brown bat and hoary bat. Bat flight activity was recorded most frequently in overmature hardwood stands (>119 years), whereas feeding was recorded most frequently in open areas ( areas of still water, along trails and in regenerating areas ranging from 0 - 9 years in age).
The authors hypothesized that, prior to European settlement, northeastern bats were inhabitants of extensive tracts of overmature hardwood timber. Bats are assumed to have used large dead and dying trees as roosts; feeding is thought to have occurred in small openings created by natural disturbances. In order to create bat habitat and maintain viable bat populations within the White Mountain National Forest, timber management plans were recommended which created small forest openings (group cuts and small clearcuts) and retained areas of older hardwoods. Intensive timber harvesting methods would be inappropriate since they would destroy the essential habitat mixture of overmature hardwood and small openings and, thus, prove detrimental to native bat populations.
Thompson, I. D. and P. W. Colgan. 1994. Marten activity in uncut and logged boreal forest in Ontario. Journal of Wildlife Management 58(2):280-288.
This study compared the movements and hunting activities of marten in conifer-dominated old-growth forest habitat with that of marten in regenerating clearcut areas. Marten experience greater survival and production rates in old-growth forest than in regenerating clearcut forests. Individuals living in logged forest had larger home ranges and acquired less energy than their foraging counterparts in uncut forest. Logged boreal forest up to 40 years old post-harvest and which was dominated by deciduous tree and shrubs was considered to be suboptimal marten habitat.
Hodgman, T.P., Harrison, D. J., Katnik, D. D. and K. D. Elowe. 1994. Survival in an intensively trapped marten population in Maine. Journal of Wildlife Management 58(4):593-600.
Maine has an estimated 25,000 mile network of logging roads, a growing network which exceeds in length the State's 22,500 miles of public highways (MaineTimes, 1/11/96). Logging road networks have the capacity to fragment forestlands and to destroy the habitat of forest wildlife. Furthermore, logging road networks increase human access to otherwise remote areas and thereby promote the overexploitation of certain sensitive wildlife species. In Maine, the marten represents one such animal whose well-being is threatened by intensive forest practices and associated logging road network expansion. The research of Hodgman et al., addresses the impact of intensive forest harvesting, fragmentation and logging roads on a marten population in north-central Maine.
In order to evaluate suspected overharvesting of marten, the authors of this study estimated age- and sex-specific survival in a population inhabiting an area of industrial forestland to the west of Baxter State Park. The area was characterized as a regenerating clearcut with interspersed mature residual forest (i.e., forest fragments); a network of logging roads provided easy access to the location. Trapping accounted for 90% of all documented mortalities. Harvests of female marten were not sustainable, and the population inhabiting the regenerating clearcut was thought to be maintained by dispersing individuals from surrounding non-logged areas, most likely Baxter State Park where marten trapping is prohibited. The authors acknowledged the connection between the high levels of marten mortality, reduced habitat quality associated with intensive timber harvesting, and trapper access via logging road networks.
Santillo, D. J. 1994. Observations on moose, Alces alces, habitat and use on herbicide treated clearcuts in Maine. Canadian Field Naturalist 108(1):22-25.
Moose usage of herbicide (glyphosate) treated and untreated clearcuts was determined for sites in north-central Piscataquis County. Vegetation availability, browse usage and pellet group surveys were used to assess the intensity of habitat usage. Browse was less available on treated sites for two years post-treatment (i.e., the duration of the study) except within areas which were inadvertently missed during the aerial herbicide application, so-called skip areas. Pellet group surveys suggested greater moose presence on untreated sites. Pellet group surveys also indicated that 73% of all pellet groups within treated sites were within skip areas, although only 15% of the total survey transects within treated sites actually traversed skipped areas. Skip areas comprised only 1-10% of the total herbicide treated area. Heavy repeat usage of browse vegetation within skip areas resulted in lower plant height and in extensive lateral growth of browse plants. In other words, moose tended to avoid herbicide treated areas, and when they did feed in clearcuts sprayed with herbicides they fed heavily in the areas which were inadvertently skipped by the spray.
Eschholtz, W. E., Servello, F. A., Griffith, B., Raymond, K. S. and Krohn, W. B. 1996. Winter use of glyphosate-treated clearcuts by moose in Maine. Journal of Wildlife Management 60(4):764-769.
This study demonstrated that on clearcuts 1 and 2 years after treatment with the herbicide glyphosate, foraging moose were 57 and 75% less abundant, respectively, than on untreated control plots. Reduced browse availability was cited as the probable reason for low moose usage.
Hix, D. M. and Barnes, B. V. 1984. Effects of clearcutting on the vegetation and soil of an eastern hemlock dominated ecosystem, western Upper Michigan. Canadian Journal of Forest Research 14:914-923.
Hix and Barnes studied the effects of clearcutting on the vegetation and the soil of an ecosystem dominated by eastern hemlock at four locations along the boundaries of the Sylvania Recreation Area (Ottawa National Forest) in western Upper Michigan. The position of commercially clearcut areas along the boundaries of the relatively undisturbed 8500-ha tract provided the opportunity to examine the effects of clearcutting after an average of 46 years post-harvest. Clearcutting resulted in the virtual elimination of hemlock from the overstory; it was replaced by a mixed forest of red maple, yellow birch, sugar maple and balsam fir. The thickness, mass and nutrient (potassium, magnesium and calcium) content of the forest floor decreased significantly, and the acidity and nutrient content of the upper mineral soil increased slightly. The replacement of hemlock by hardwoods has slowly decreased the acidity and apparently increased the rate of nutrient cycling. The authors conclude that without major disturbance, such as fire, hemlock is not likely to regain dominance following clearcutting owing to its inability to regenerate naturally.
Buchert, G.P., Rajora, O.P., Hood, J.V. and Dancik, B.P. 1997. Effects of harvesting on genetic diversity in old-growth eastern white pine in Ontario, Canada. Conservation Biology 11(3):747-758.
Under conditions of intensive harvesting, the genetic make-up of residual, or post-harvest, trees may be altered. Subsequently, the regenerating progeny of such residual trees may lack genetic diversity and thereby be unable to cope with a range of environmental challenges which were met successfully by their pre-harvest ancestors.
Measures of genetic diversity were compared between pre-harvest and post-harvest gene pools of two adjacent virgin, old-growth (approximately 250 years old) stands of eastern white pine in central Ontario. The harvest (a partial cut) resulted in a 75% reduction in the breeding population of the two stands. A comparison of pre-harvest and post-harvest gene pools indicated a substantial loss of genetic diversity resulted from the harvest. The authors acknowledged the possibility that pollen migration from adjacent non-harvested stands might off-set the genetic loss. However, where all white pine stands on the immediate landscape are harvested, the probability of genetic loss amelioration by pollen migration is diminished.