Effects of woody debris and ferns on herb-layer vegetation and deer herbivory in a Pennsylvania forest blowdown

Abstract

Disturbances create a variety of legacy types, which can influence subsequent forest dynamics. One method by which legacies may influence succession is by altering herbivore activities. For example, logging slash has been shown to be effective in preventing browsing by large herbivores. Generalizing from studies after logging, we hypothesized that windthrow slash (woody debris) would limit the ability of deer to reach or locate individual plants. Furthermore, another legacy of disturbances is the establishment of recalcitrant vegetation, such as dense fern layers, which subsequently preclude woody plant establishment. To test for potential influences of these 2 types of legacies, we examined the effects of slash and fern abundance on herb and woody community structure and deer herbivory levels within a Pennsylvania windthrow gap. Slash abundance was negatively correlated with woody diversity, richness, black cherry seedling densities, and total seedling densities, but this effect was probably not a consequence of browsing. Fern abundance was negatively correlated with woody richness, red maple densities, total seedling densities, herb diversity, and richness. Fern effects on the woody community appeared to be related to reductions in light availability. Our results contradict the findings of previous studies that show that slash piles serve as refugia from herbivores. We suggest the inconsistencies may be due to a lack of quantitative measures of slash within those studies.