Differential Response of Microbial C, N, and P and Their Stoichiometry at Different Soil Depths to Precipitation in Arid Desert Soils

The responses of microbial C, N, and P to precipitation at different soil depths and corresponding stoichiometry are important for further development of arid desert models pertaining to global climate change. In this study, we conducted a precipitation control study to investigate the effect of extreme drought, moderate drought, natural precipitation, moderate precipitation, and extreme precipitation, on microbial C, N, and P, as well as their stoichiometries, at soil depths of 0–5, 5–10, and 10–20 cm. Results indicated that the five precipitation treatments caused a constant decrease in microbial C, N, and P contents at soil depths of 0–20 cm. At soil depths of 0–20 cm, moderate precipitation resulted in the decreasing trends of microbial C : N (8.10 to 5.38) and C : P (106.13 to 67.08) and N : P (13.10 to 12.47), moderate drought caused microbial C : P (83.07 to 63.10) and N : P (13.43 to 5.27) to decrease but microbial C : N (6.18 to 11.97) to increase. Also, extreme precipitation may lead to microbial N limitation at soil depths from 5–20 cm, while extreme drought and moderate precipitation may enhance microbial P limitation at depths from 0 to 20 cm. The soil profile indicated that microbial C, N, and P in the upper soil layer significantly affected microbial C : N, C : P, and N : P ratios in the lower soil layer under moderate and extreme precipitation. Overall, our findings demonstrated that short-term changes in precipitation did not affect the decreasing trends shown by microbial C, N, and P at soil depths from 0–5 to 10–20 cm, as also the responses of microbial C, N, P to precipitation as well as their corresponding microbial C : N, C : P, and N : P ratios tended to be different at different depths of arid desert soils.