Natural and anthropogenic disturbances alter resource availability and consequently create environmental conditions which favor certain competitive traits over others. High severity disturbances, for example, often favor plant species with high growth rates, shade intolerance, and wind-dispersed seeds, while low severity disturbances typically favor contrasting traits. Assessing plant community composition and associated life history traits across a broad range of disturbance severities may therefore better inform forest managers and ecologists alike. Moreover, disentangling the effects of canopy and forest floor disturbances, which often co-occur, on plant community composition could provide valuable insight into how forests respond to disturbances and ultimately, how to best manage for ecosystem resiliency in the face of global change. The objectives of this study were to 1) compare the magnitude of plant community resilience to management-based canopy and forest floor disturbances, and 2) identify how life history trait composition responds to a gradient of canopy and forest floor disturbances. To test our hypotheses, we implemented a range of silvicultural disturbances including harvesting and site preparation treatments. Plant community patterns were assessed before and two consecutive growing seasons after treatment application and compared to microsite conditions such as light availability, leaf litter depth, and soil water content.
Results/Conclusions
Overall, we found a strong effect of canopy disturbances on plant community composition, which was mediated by changes in microsite conditions. Moreover, divergences in composition of life history traits such as growth form and fruit type may underly plant community responses. Canopy disturbances favored herbaceous species with low mass fruits such as achenes, capsules, and schizocarps. Forest floor disturbances shifted species and fruit type composition but had no detectable effect on growth form composition. Overall, canopy disturbances appear to have a greater effect on plant community structure than forest floor disturbances, suggesting greater initial resilience to forest floor disturbances in northern hardwood forests. A complete understanding of resilience, however, will require longer-term monitoring of plant community responses beyond two years post-disturbance.