Temperature regulates the effects of N and P addition on straw decomposition and soil organic carbon dynamic in black soil
摘要
Temperature governs how N and P additions influence straw decomposition. P fertilization at low temperature triggers SOC loss via microbial priming. Climate-smart P management is vital to sustain SOC in cold agricultural soils.
The decomposition of returned straw is critical for sustaining soil organic carbon (SOC), particularly in black soils (Mollisols) that experience prolonged low-temperature periods. Although low temperature is a major constraint on microbial activity, how nutrient stoichiometry regulates microbial processes under low-temperature conditions remains unclear. Through a 150-day incubation experiment, we found that temperature strongly regulates the effects of nitrogen (N) and phosphorus (P) fertilization. Straw decomposition was primarily temperature-dependent, increasing from 5 °C to 15 °C. NP fertilization accelerated decomposition only at 15 °C, where it mitigated microbial nutrient co-limitation. Conversely, at 5 °C, P and NP addition did not promote straw decomposition but were associated with significant losses of SOC. This pattern was accompanied by higher activities of C- and N-acquiring enzymes (BG and NAG) and enrichment of decomposer taxa such as Gemmatimonas, suggesting a shift in microbial metabolism toward the utilization of soil C. These results reveal a low-temperature carbon paradox: under cold conditions, nutrient addition may fail to enhance straw decomposition while instead promoting the turnover of SOC. Our findings highlight the importance of optimizing P management in cold-region agriculture systems to maintain soil C storage.