Frequency of stover mulching but not amount regulates the decomposition pathways of soil micro-foodwebs in a no-tillage system

摘要

In soil micro-foodwebs, resource-transfer links between bacteria, fungi and microbivorous nematodes govern the transformation and `cycling of soil organic carbon and for the quality, productivity and sustainability of soil ecosystems. However, changing the amount and frequency of stover mulching affects the resources available for the bacterial versus fungal decomposition pathways of soil micro-foodwebs. Therefore, we investigated the responses of the soil micro-foodweb to maize stover mulching amounts (33% and 67% of the stover remaining at harvest) and frequencies (high frequency had continuous mulching every year; low frequency had mulch applied once every three years) during a 10-year mulching experiment in a no-tillage system. Soil microorganism and nematode communities were affected significantly by the frequency, but not the amount of stover mulching. Greater abundance of bacterial PLFAs that were correlated with bacterivores occurred in the high frequency mulching treatments. In the low frequency mulching treatments, the abundance of fungal PLFAs and their correlations with fungivores were higher. Greater nematode enrichment index in the high frequency mulching indicated more carbon flow from mulch into the soil micro-foodweb, whereas low frequency mulching tended to develop a relatively stable soil micro-foodweb. We conclude that trophic interactions regulate the binary coupling between bacteria and bacteriovores with high frequency mulching and between fungi and fungivores with low frequency mulching. Consequently, the structure and activity of decomposition pathways in these soil micro-foodwebs are determined by the bottom-up effect of stover mulching.