The forests of the northeastern United States are more fragmented and less vigorous as a result of exposure to acid rain, ice storm damage, pest outbreaks, and forest diseases. Often, these invading and pervasive threats target important mast trees. Beech bark disease (BBD) is widespread and complex, as it involves a scale insect pest (Cryptococcus fagisuga) and an opportunistic fungus (Nectria spp.). In this study, we explored the potential effects of BBD on the diversity of small mammal assemblages in northern hardwood forest. In the summer of 2007, preliminary forest disease and small mammal surveys were performed in Newcomb, NY (Adirondack Park) as well as Claryville, NY (Catskill Park) to provide a baseline inventory for future investigation. In 2008, a hardwood forest survey was undertaken in the above-mentioned sites as well as in Altona, NY (Champlain Valley) and North Shrewsbury, VT (Green Mountains). We hypothesized that sites further north would experience greater disease levels, mast fewer beechnuts, and thus be dominated by fewer seed predators in the small mammal guild. For four consecutive days in June 2008, small mammals were sampled using ninety Sherman live-traps traps at sites. Disease intensity was quantified using the Griffin et al. (2003) ranking scale and mast was collected in seed traps. Since insect and disease damage has been known to reduce mast, we predicted that diversity among small mammal assemblages would vary according to site and small mammal biodiversity would be reduced in heavily diseased stands.
Results/Conclusions
The greatest to least diverse community of small mammals was observed in the Champlain Valley, Catskills, Green Mountains, and the Adirondack sites respectively, according to Shannon-Weiner diversity indices. Although there was not a statistically significant difference in diversity among sites, there were significant differences in dbh and disease state. Fall 2008 mast collection suggests that the highest average yield of beechnuts occurred in the Catskill, and Vermont forest stands. Perhaps most significant was that in the summer prior to the 2007 non-mast year, the majority of small mammals captured were (Peromyscus spp.), whereas in the summer prior to mast-year 2008, assemblages were dominated by woodland jumping mice (Napaeozapus insignius). This turn-over in species following the 2 year beech masting cycle suggests that reproduction in seed-predating Peromyscus spp. may abound, to the exclusion of woodland jumping mice. Woodland jumping mice diets are known to diverge from seeds to root fungus, giving them an advantage in seed depauperate years.
