COS 48-2
Impacts of past agricultural land-use on forest herb community composition and dynamics
The legacy of past land-use in successional forest is well-documented, but the impacts of specific agricultural practices are less understood. The purpose of this study was to examine the mechanisms of recolonization by forest herbs and the dynamics of herb communities on post-agricultural land, with an emphasis on contrasting plowed fields and unplowed pastures through successional time. We tested the hypotheses that slow-dispersing species will be more common on pasture sites due to the possibility of survival below ground and that community composition and structure on plowed sites will reflect the homogenization inherent in this form of land-use.
In a paired chronosequence, forest sites occupying abandoned pastures and cultivated fields were grouped into three age classes, and a control group of minimally-disturbed mature forest. Stand age was estimated from historical aerial photographs. Land-use history was determined using historical photographs and site characteristics including surface microtopography and soil profiles. Herbaceous vegetation and environmental variables were sampled at each site in an array of 2 x 2 meter plots.
Results/Conclusions
Environmental variables show significantly less microsite heterogeneity in plowed sites. Slow-dispersing species were significantly more frequent in young pastured sites, occurring in small spatially compact populations, but not cultivated stands of equivalent ages. Forest species are concentrated near streams and other landscape features. Conformity of forest species with landscape features on pastured sites suggests that environmental screening occurs early in secondary succession. These findings indicate that the severe soil disturbance and homogenizing effects of cultivation leave a lasting impact on the composition and structure of forest vegetation.