WAT04 Root decomposition and nutrient dynamics are resistant to rainfall legacies in tallgrass prairie

Purpose: Litter decomposition is an important component of carbon (C) and nitrogen (N) cycling, and rates of mass loss and nutrient release are sensitive to current climate conditions. Growing evidence suggests that past climate conditions can exert legacies on soil C and N cycling, but little is known about how belowground decomposition dynamics relate to these climate legacies. Results: Root litter mass loss was resistant to most climate treatments. Contrary to expectations, decomposition rates were slowest in plots with a history of long-term irrigation and fastest under drought in lowland prairie. Similarly, mass loss rates were overall faster in the drier uplands. Changes in N concentration as a function of mass loss were similar across treatments and patterns of litter N release largely tracked mass loss. Conclusions: Changes in the decomposer community with long-term release from water stress may have led to slowed root decomposition, but these effects were subtle. Our results suggest that changes in decomposition rates are not a cause of observed climate legacy effects on C and N cycling in prairies.