Tornados are common natural weather phenomena which highly influence ecosystem structure and function. In eastern deciduous forests, tornados often cause a substantial amount of physical damage, which greatly decreases the spatial heterogeneity of the forest. Forest blowdowns remove forest canopy and substantially increase the amount of course woody debris, which creates refugia for small mammals. A tornado struck the area of Ligonier, PA on 1 June 2012, creating a path of severe canopy damage about 8 miles long and affecting about 90 acres of forest. Following the tornado, experimental forest management for each blowdown area was initiated which included salvage logging, no salvage logging, and control (unaffected forest). Our objective was to examine impacts of a tornadic blowdown and subsequent forest management on the small mammal assemblage in the eastern deciduous forest. In Nov 2013, we established an extensive small mammal live-trapping grid across both forest treatments and control forest, with trapping occurring seasonally (spring, summer, and fall). Traps were baited with rolled oats and custom-made baitballs. Small mammals were ear-tagged, and data collected included trap station, species, sex, age class, body mass, and body and reproductive condition.
Results/Conclusions
The small mammal assemblage was composed mainly of Peromyscus leucopus and Clethrionomys gapperi. Seven other species were trapped less frequently, including Blarina brevicauda, Sorex cinereus, S. hoyi, Glaucomys volans, Tamias striatus, Napaeozapus insignus, and Microtus pennsylvanicus. To date, we have amassed >3100 trap-nights, >1000 animals captured, and an overall trapping success rate of >30%. Overall, more small mammals were found in the blowdown area than expected. Small mammals tend to increase in frequency in the blowdown area from spring to fall concomitant with increased overall small mammal population sizes. Capture success in the blowdown area generally is higher, especially in the fall. Small mammals found in early successional stages of the blowdown included Microtus pennsylvanicus and Napaeozapus insignus, but they are no longer present. Small mammals in both salvage and non-salvage blowdown areas were found to have lower body masses and skewed sex ratios compared to those in control areas. Age, sex, and body mass differences of the two most frequently trapped small mammals were seen in salvage treatment compared to the other treatments. Although these mammals all strongly prefer forested habitat, the added complexity of the ground cover (through course woody debris and succession) seems to make the blowdown area one of opportunity for small mammals willing to occupy it.