Presenter : Geoffrey Johnson
Mentor : Scott Bridgham
Major : Environmental Science
Poster 31
Plant litter from aboveground and belowground production constitutes a major carbon (C) and nutrient input to forest soils worldwide. Uncertainty in the relative effects of these two biomass allocations on ecosystem structure and function is the impetus for the Detritus Input Removal and Transfer (DIRT) experiment, which incorporates root trenching and leaf litter removal and addition. In this study, we sampled mineral soils from DIRT plots at a temperate hardwood forest in Northwestern Pennsylvania in the 0-10 cm depth for all treatments and additional organic horizon and 10-20 cm profile depths for control (CO) and double litter (DL). This DIRT site was established in 1991. By incubating samples at 35°C and near-optimal moisture content for 56 weeks, we estimated maximum potential respiration and net nitrogen (N) mineralization and used the resulting cumulative values to compare rate constants and pool sizes for 1 and 2 pool exponential models among treatments. Net N mineralization in DL plots was significantly greater than CO (α=0.05) at 10- 20 cm, while the no input (NI) treatment was significantly less than CO and DL (α=0.05) at 0-10 cm. We also provide evidence that the treatment effects will continue to become more significant on longer time-frames. From these results, we suggest soil C and N pools are affected by plant litter allocation ratios on decadal time scales, and the most rapid effects may be outside of the pools in the uppermost mineral soil horizons.