Effects of soil organism interactions and temperature on carbon use efficiency in three different forest soils

Abstract

Microbial carbon use efficiency (CUE) affects the soil C cycle to a great extent, but how soil organisms and the abiotic environment combine to influence CUE at a regional scale remains poorly understood. In the current study, microcosms were used to investigate how microbial respiration, biomass, and CUE responded to biotic and abiotic factors in natural tropical, subtropical, and temperate forests. Soil samples from the forests were collected, sterilized, and populated with one or a combination of three types of soil organisms (the fungus Botrytis cinerea, the bacterium Escherichia coli, and the nematode Caenorhabditis elegans). The microcosms were then kept at the mean soil temperatures of the corresponding forests. Microbial respiration, biomass, and CUE were measured over one-month incubation period. The results showed that microbial biomass and CUE were significantly higher, but microbial respiration lower in the subtropical and temperate forest soils than in tropical forest soil. Biotic factors mainly affected CUE by their effect on microbial biomass, while temperature affected CUE by altering respiration. Our results indicate that temperature regulates the interactive effects of soil organisms on microbial biomass, respiration, and CUE, which would provide a basis for understanding the soil C cycle in forest ecosystems.