Does leaf litter diversity affect soil microbial community structure and functions in Chinese subtropical forest?
Biodiversity loss has generated unprecedented concerns for its consequences on ecosystem functioning and services. Decomposition and nutrient cycling are ecosystem functions that are likely altered by changes in forest biodiversity, but most knowledge on this topic is from temperate ecosystems, or is based separately on either microorganisms or on their subsequent functions. The objective of this research was to determine the microbial composition and functions responses to litter diversity during decomposition process in a subtropical forest. This decomposition experiment was part of the Biodiversity and Ecosystem Function-China (BEF-China) project, situated in southeastern China. Litter from seven local tree species, combined into two overlapping species pools were used to create replicates of three levels of litter diversity mixtures (1, 2, and 4). Different species diversity treatments of litter samples were added into mesocosms in 11 plots, replicated four times in four corresponding blocks. Soil samples were taken at four time-points, 21, 49, 105, and 168 days after the plot establishment. Microbial community composition was measured only at the third time point using lipid analysis. Microbial functions were observed at each time point during the whole decomposition process. Phenol oxidase, peroxidase, b-glucosidase, xylosidase, N-acetyl-glucosaminidase and acid phosphatase were measured for indicating microbial decompositional function and gross nitrogen mineralization and nitrification rates represented the microbial nitrogen cycling.
We observed litter species diversity effects on soil microbial community composition and arbuscular mycorrhizal fungal abundance, as a result of substrate heterogeneity and microbial habitat diversity provided by the litter species mixture. Our results also indicate that phenol oxidase and peroxidase were significantly correlated with the soil microbial community composition, implying that ligninlytic enzymes are more closely related to community structure, and that microbial community structure could determine microbial function in this subtropical ecosystem. We also found that enzyme activities were influenced by sampling time, soil moisture, and litter mass remaining, rather than litter diversity per se. In conclusion, litter diversity only affected microbial community structure, but there were positive relationships between microbial structure and functions. In addition, lignolytic enzymes are more sensitive to the microbial community shift than the cellulose degrading enzymes.