Comparatively large and diverse populations of reptiles and amphibians (collectively called herpetofauna or herps) inhabit all forests of the eastern United States. Only a few detailed long-range studies have measured the effects of clearcutting on their populations.
Most studies in the eastern United States indicate that more amphibians are present in mature forest stands compared to young successional stages. Amphibian populations in 2- to 20-year-old clearcuts were compared to populations in mature hardwood and hardwood-conifer forests by Blymer and McGinnes (1977), Enge and Marion (1986), Pough et al. (1987), Ash (1988), DeGraaf and Yamasaki (1992), Petranka et al. (1993, 1994), Soehn and Michael (1995), and deMaynadier and Hunter (in preparation). All these studies found higher amphibian abundance (2.3 to 9.3 times as many) on the mature plots. With the possible exception of an unreported forest type in Virginia and a slash pine forest type in northern Florida, all studies were located at high elevations or in the northeastern region.
Based on an examination of data sets by deMaynadier and Hunter (1995) on amphibian captures in clearcut vs control stands throughout North America, plethodontid salamanders generally experienced greater population declines in clearcut stands than any other amphibian group. One of the most important factors affecting amphibian abundance appears to be forest litter depth, particularly in eastern hardwood forests (Pough et al. 1987, DeGraaf and Rudis 1990, Bonin 1991). “This suggests that forest harvesting practices that minimize soil compaction and litter disruption or type conversion might shorten the length of recovery time for amphibian species associated with a particular microhabitat” (deMaynadier and Hunter 1995).
Because of abundant moisture and woody debris, amphibian response to clearcutting may be less dramatic in forested wetlands than in other habitats. In studies of wetlands by Pais et al. (1988), Foley (1994), Phelps and Lancia (1995), and Clawson et al. (1996), in mixed mesophytic deciduous hardwood regions in Kentucky and in bottomland hardwoods of South Carolina, southern Alabama, and southern Texas, herpetofaunal species richness and abundance were not significantly different between clearcuts and uncut areas. In contrast, in the dry sand pine-scrub oak habitat of central Florida, southern toads were found in greater numbers in young stands (Christman et al. 1996). The abundance and richness of herpetofauna decreased as the sand pine stands matured.
Herp response to clearcutting varies with forest type, taxa, and other ecological considerations as well. Evidence that habitat variations can affect herp populations differently following forest disturbance was illustrated by the following study conducted in the Coastal Plain of the South. Pearson et al. (1987) compared herp numbers present in longleaf pine-slash pine stands of southern Mississippi, in mature, uncut bayheads and in the following pine stand age classes: regeneration (clearcuts), sapling, pole, and sawtimber. The highest number of salamanders were recorded in
bayheads. Toad, frog, turtle, and lizard diversity was similar across all types. Lizards were most abundant in poletimber stands. Snake diversity was lowest on regeneration areas.
Prescribed and natural fire is wide-spread in the Coastal Plain of the southeastern United States. Mushinsky (1985) studied herp numbers in experimental burn plots of 3 fire frequencies (1, 2, and 7 years) and in a control plot unburned for 20 years in slash pine habitat of south Florida. Data on 9 species of amphibians over a 2-year period of study indicated that the control plot had fewer total captures than any of the burn plots. He also found that plots burned annually produced high numbers of species and individuals. In northern Florida, Means and Campbell (1981) compared herps in 2 regularly burned forest types (longleaf pine and shortleaf pine) with an unburned beech-magnolia climax forest. Three amphibian species occurred more frequently in the regularly burned pine forests.
Concern for the gopher tortoise, an edible reptile also found in the sandy regions of the southeastern Coastal Plain, resulted in studies to determine factors responsible for their apparent decline. Reports by Landers and Garner (1981), Auffenberg and Franz (1982), Lohoefener (1982), and Diemer (1986) indicated that a major factor affecting the decline was the cessation of prescribed burning which encouraged the development of a dense midstory and in turn discouraged the growth of plants made suitable as food for the tortoise. Other detrimental influences included management
for dense stands of pine, conversion of forest lands into agricultural and urban areas, and the poaching of tortoise for food and pets.
b. Site Preparation
Intensity of site preparation has been found to affect the composition of herpetofaunal communities. In general, amphibians appear to be more sensitive to intensive site preparation methods than do reptiles. The effects of clearcutting and site preparation on amphibian species richness in pine flatwood habitats of north Florida were studied by Enge and Marion (1986). Herps included 18 amphibians (2 lungless), lizards, snakes and other reptiles. Amphibian species richness was not immediately affected, but later, richness was reduced 10-fold by reductions in reproductive success. Reptile abundance was reduced by maximum site preparation but not by minimum site preparation. Overall herp biomass was not adversely affected by clearcutting and minimal site preparation.
Another study of amphibian populations in the same forest type, but on an open, wet savanna which had been cleared, roller chopped, mechanically bedded, and planted to slash pine, was reported by Means et al. (1996). Breeding season migrants, which included the flatwoods salamander, decreased over a 20-year period from 7.9 individuals seen per hour to 0.1 per hour. This decrease was attributed by the authors to the effect of intensive site preparation.
A study was conducted by Greenberg et al. (1994) 5- to 7-years after site preparation treatments to determine the effects on reptile species richness and diversity in the sand pine-scrub oak habitat of central Florida. Treatments included high intensity burns, roller chopping, and brake-seeding. Reptile species richness and diversity did not differ among treatments nor between the treated area and the mature forest. Species composition, however, differed markedly. The six-lined race-runner, Florida scrub lizard, and mole skink were dominant in the high intensity burn and site-
prepared stands but scarce in the mature forest. Conversely, the southeastern five-lined skink was most abundant in mature forest, a finding correlated with the abundance of ground litter.
Most studies have used second-growth forests as controls. The population recoveries noted indicate that there is no reason to suspect diversity cannot be maintained over time. Yet, none have adequately considered landscape-scale impacts of harvesting. It is reasonable to hypothesize that even though salamanders may decline in some newly harvested stands, they still may exist in high numbers in adjacent, mature, second-growth stands. Thus, responses of amphibians at the landscape scale may differ from those at the stand scale.Next page...Effects of Clearcutting on Forest Vegetation