Effects of Detritus Treatments on Soil Microbial Community Composition, Structure and Nutrient Limitation in a Subtropical Karst Ecosystem

Detritus inputs and removal strongly influence soil carbon (C), nitrogen (N), and phosphorus (P) as well as soil microbial communities and resource limitations. Here, we characterized soil microbial communities using 16 S rRNA and ITS amplicon sequencing and ecoenzymatic stoichiometry to explore how detritus treatment mediates nutrient limitations and microbial community characteristics in a subtropical karst ecosystem. Our DIRT (Detritus Input and Removal Treatment) experiment elucidates relationships between soil nutrients, microbial biomass, and enzyme activities and microbial community composition, structure, and nutrient limitation in karst soil. Detritus treatment was associated with significant differences in soil nutrient content, microbial biomass, and enzyme activities. Analysis of soil enzymatic vectors suggested that microbial communities became less N- but more P-limited under detritus inputs. Detritus treatment also altered microbial community composition but did not significantly influence microbial diversity. Redundancy and correlation analyses revealed strong positive associations between nutrient limitation and soil nutrient content and microbial biomass, suggesting that microbes adjust soil microbial biomass to improve nutrient restriction. Partial least squares path modeling further revealed that soil nutrients were the main factor controlling microbial nutrient limitation in this karst ecosystem. Double litter input significantly increased soil nutrient, microbial biomass, and enzyme activities and shifted microbial nutrient limitation from N- to P-limited. In contrast, detritus removal decreased soil C, N, and P content, thereby influencing soil nutrient cycling. This our research investigates the effects of detritus input and removal on soil nutrient status and soil microbial community characteristics, which, to our knowledge, has not been explored. Our findings improve understanding of karst ecosystems and will inform guidelines for restoration efforts in karst rocky mountains.