Chemical quality of litter as a driver of detrital community assemblage in mineral soil

Although much attention has been given to the amount of resources regulating populations in soil, the quality of resources may be their strongest driver. Studies dealing with the effect of litter quality on soil communities have focused on the litter populations; however, how the mineral soil communities respond to the chemical quality of surface litter can have implications in soil carbon and nutrient dynamics. In a field setting we studied the short-term effect of surface application of five plant materials and a mixture on the microbial community, nematodes and microarthropods in mineral soil. We used five substrates and a mixture to determine (a) the effect of substrate type on mineral soil communities and (b) which biochemical parameters most influenced the soil micro-food web groups’ abundance during the first six months of decomposition. We identified some patterns of response by microbial groups.  Fungi and Gram-negative bacteria responded positively to high nutrient content and Gram-positive bacteria and actinomycetes were stimulated by high %C and % lignin. C/N was the main driver of the fungi-to-bacteria ratio. Different quality variables were related to the responses of the soil community at different times. Early during decomposition those responses were related with nutrient content while later %C, %lignin and lignin-to-N had the greatest influence. Bacterial-feeders and omnivorous nematodes response was correlated with the response of bacteria. No pattern of response by microarthropods was observed. Thus quality influenced populations in soil at different trophic levels and has the potential to influence processes that are driven by trophic interactions.