Impacts of management legacies on litter decomposition in response to reduced precipitation in a tallgrass prairie

Abstract

The response of ecosystem processes to current and future climatic events may be affected by historical disturbance regimes. Here, we address the interaction between reduced precipitation and the legacy effects of two contrasting long-term burn regimes in a tallgrass prairie (20 years of annual burning versus fire suppression). We examined rates of decomposition and the response of decomposition to reduced precipitation under rainout shelters in these two prairie types to assess potential interactions between legacy effects and reduced precipitation. To test the legacy effects of the different burn regimes, we placed experimental plots in each prairie type under a standardized management regime. In each plot, we ceased burning, mowed to maintain a standard canopy height, and maintained standard surface litter accumulation. We measured decay rates for surface litter, buried roots, and buried wooden dowels. While decomposition rates of substrates were reduced an average of approximately 29% under reduced precipitation, we found no significant main effects of burn history on decomposition on any of the substrates. However, in the recovery period following 2 years of an experimentally imposed drought, we did find an effect of burn history on decomposition and this effect varied for different substrates. Historical effects of management or natural disturbances on ecosystem processes may often be subtle or negated by compensatory responses, and in this study few legacy effects on decomposition rate were detected.