Characteristics of soil microbial respiration and its response to temperature change in different soil depths in Yunwu Mountain grassland

Soil respiration and its temperature sensitivity are two important parameters to predict carbon cycling. In the Loess Plateau region, however, soil microbial respiration and its temperature sensitivity at different soil depths have not been investigated. This study focused on the characteristics of soil microbial respiration and temperature sensitivity at different soil depths, by taking advantage of a typical grassland in the Yunwu Mountain Natural Conservation area of the Loess Plateau, which has been fenced for 30 years. In this study, soils were sampled from different soil layers (0-10, 10-20, 20-30, 30-40, 40-50, and 50-60 cm) and incubated at 25 ℃ or 35 ℃, and the changes of soil respiration were examined. We found that soil organic carbon, total nitrogen, available nitrogen, available phosphorus, total phosphorus, microbial biomass carbon, and microbial nitrogen contents decreased significantly with increasing soil depth (P<0.05). In addition, soil respiration rate and cumulative C loss by respiration at both temperatures significantly decreased with increasing incubation period and soil depth (P<0.05). However, temperature sensitivity showed an increasing trend with increasing soil depth. Redundancy analysis showed that soil respiration rate was positively correlated with soil properties, while temperature sensitivity of soil respiration was negatively correlated with all soil factors.