Drought impacts and recovery are driven by local variation in species turnover.

摘要

In forest systems, drought acts as a disturbance that can generate impacts on community structure and composition at multiple scales. This study focused on a 2-month drought event within an early successional forest system to determine the mechanism(s) of community response to, and recovery from, drought. Data collected from an abandoned agricultural land in the Piedmont region of New Jersey, USA were used. Acer, Quercus and Juniperus virginiana were the dominant species in the canopy of the fields. Drought induced a 28% decline in neighbourhood species richness and cover as a result of decreased colonization and increased extinction rates. Following drought, neighbourhood richness quickly recovered via increased colonization rates while extinction rates were unaltered. Drought had little long-term effect on neighbourhood structure (species richness and cover) and generated only subtle changes in neighbourhood composition. Ruderal (annual and biennial) species were more likely to change (increase or decrease) in cover and frequency than the more stress tolerant perennial and woody species. However, population dynamics appeared to be generally driven by stochastic species turnover among fields and not by uniform shifts in species performance across the site. Although drought impacts and recovery appeared predictable at the neighbourhood scale, population responses to drought within the site were rather unpredictable. Our findings suggest that stochastic fine-scale processes can generate predictable course-scale dynamics within a disturbed system. The scale-specific mechanisms of community change presented here should be explored in other systems to determine the extent of their generality in driving disturbance impacts on communities..