Litter composition effects on decomposition across the litter-soil interface

Background/Question/Methods

Many studies have investigated the influence of plant litter species composition on decomposition dynamics, but given the variety of communities and environments around the world, a variety of consequences of litter-mixing have been reported. Litter and soil are considered to constitute a decomposition continuum, with resources moving from the litter into the soil, but whether litter and soil ecosystems respond to litter identity and mixing in the same manner is unsure. In a field experiment conducted in an abandoned conventional farm in the piedmont region of Georgia utilizing 5 litter species and their mixture, we investigated whether the effects of litter identity and mixing on mass loss, nutrient dynamics, and decomposer communities are consistent across the litter-soil interface.

Results/Conclusions

In monoculture, mass loss and nitrogen (N) dynamics in the litter layer corresponded to the underlying soil N availability, demonstrating the continuum of resources from litter to soil. After 6 months of decomposition, the litter species decomposing the fastest and releasing the most N hosted a larger microbial and mesofauna community, while the slowest decomposing species releasing the least N hosted a smaller microbial and mesofauna community. However, the soil decomposer community did not respond in the same manner. Soil community abundance and diversity were not correlated with decomposition rate or N. Non-additive mass loss and N dynamics were observed after 6 months, and were correlated with non-additive litter bacteria:fungi and mesofauna abundance. Decomposer communities and N dynamics did not respond similarly to litter-mixing across the litter-soil interface. This study is one of the few to comprehensively examine how litter-mixing influences decomposition dynamics and communities across the soil-litter interface, including multiple taxa and trophic levels. Our results demonstrate that the controls on decomposition dynamics in the litter are not necessarily paralleled in the soil, particularly in how they respond to litter-mixing.