Experimental warming and clipping altered litter carbon and nitrogen dynamics in a tallgrass prairie

Litter carbon (C) and nitrogen (N) dynamics are important processes in regulating C and N cycling in ecosystems. However, it is not well understood how global climate change and land use practice interactively affect litter C and N dynamics in ecosystems. We conducted a field experiment in a tallgrass prairie in Oklahoma, USA, to study effects of climate warming and clipping (as mimic of agricultural hay harvest) on litter C and N dynamics in association with litter production and decomposition of dominant species C₄ grass and C₃ forb. Warming did not significantly affect specific decomposition and N immobilization/mineralization rates of either species but increased C₄ and decreased C₃ litter production. Increased C₄ litter production, together with its intrinsic low decomposition, resulted in 16-47% increase in litter mass. Warming decreased N concentrations, litter N production, litter N pool and litter N output (i.e., litter N loss). Clipping significantly increased specific decomposition rates of C₄ litter but decreased litter production, litter mass and litter N contents. Our results suggest that indirect effects of climate change via shifts in plant species composition and decreases in litter quality are much more important than its direct effects on litter decomposition and subsequent C and N turnovers.