Idiosyncratic responses of microbial communities and carbon utilization to acid rain frequency in the agricultural and forest soils

Abstract

Abstract The level of acidity in rainfall can alter soil nutrient cycling (e.g., carbon [C] cycling), while the effect of changing acid rain frequency on soil C cycling and involved microbial communities remains largely understudied. Here, we manipulated a laboratory intact soil core experiment to test the effect of acid rain frequency (0, 30% and 100%) on soil CO2 emission, microbial communities, and microbial metabolism of various carbon sources in the agricultural and forest soils in southern China. We found idiosyncratic responses of soil microbial communities and carbon utilization to acid rain frequency in two different soil ecosystems. The high acid rain frequency (100%) substantially reduced soil microbial biomass, particularly that of gram-negative bacteria in the forest soil, while this effect was not observed in the agricultural soil. Moreover, acid rain frequencies (30% and 100%) significantly reduced the microbial utilization of amines/amides in the agricultural soil, while they did not alter the carbon sources utilization in the forest soil. However, surprisingly, both the acid rain treatments did not affect the soil CO2 emission in the agricultural and forest soils, suggesting a complex relationship between soil microbial biomass or abundance and CO2 emission. Our results suggest that the agricultural and forest soils have idiosyncratic responses to changing acid rain frequency, probably because of differences in their biological and physicochemical properties.