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.
We conducted a two-year root decomposition experiment in a long-term precipitation manipulation study in a tallgrass prairie (Kansas, USA). Irrigation was used to mitigate water stress for ~25 years; irrigation and ambient rainfall treatments were then reversed in a subset of plots, and a drought treatment was added in both previously irrigated and ambient treatments. This design allowed us to assess the independent and interactive effects of past and current precipitation regimes on root decomposition.