Seasonality regulates the effects of acid rain on microbial community in a subtropical agricultural soil of Southern China

Abstract

Acid rain alters soil carbon (C) cycling by influencing the soil microbial community structure and functions. However, the response of soil microbial communities to acid rain with time and underlying mechanisms are still poorly understood. Herein, we conducted a one-year intact soil core experiment to investigate the temporal changes of soil microbial community composition and C sources metabolism under acid rain (pH 5.0, pH 4.0, and pH 3.0) in an agricultural soil of southern China. We found that pH 3.0 acid rain increased the total, bacterial, gram-positive bacterial, and actinomycetal PLFAs at the early stage, but this effect diminished with time. Conversely, the gram-negative bacterial PLFAs contents were reduced under pH 3.0 acid rain at the later stage. Interestingly, pH 5.0 acid rain increased the total, bacterial, gram-positive bacterial, and actinomycetal PLFAs contents at the later stage. In addition, pH 3.0 and pH 5.0 acid rain treatments accordingly altered the soil microbial community structure at the early and later stage. However, acid rain did not change the microbial C sources utilization pattern. The principal response curve analysis revealed that the seasonal variation exerted a greater effect on the overall variance of soil microbial community structure than the acidity of acid rain. Our results demonstrate the asynchronous response of soil microbial community structure and function, which implies that the microbial functional redundancy may exist in the subtropical agricultural soil under acid rain.