| 英文摘要： |
Background Nitrogen (N) and phosphorus (P) deposition have largely affected soil respiration (R-s) in forest ecosystems. However, few studies have explored how N and P individually or in combination to influence R-s and its components (autotrophic respiration, R-a; heterotrophic respiration, R-h), especially in highly P-limited subtropical forests. To address this question, we conducted a field manipulation experiment with N and/or P addition in a 50-year-old subtropical secondary forest. Results We found that N addition on average reduced R-s, R-a, and R-h by 15.2%, 15%, and 11.7%, respectively during 2-year field study. P addition had an inconsistent effect on R-a, with R-a increasing by 50.5% in the first year but reducing by 26.6% in the second year. Moreover, P addition on average decreased R-h by 8.9%-30.9% and R-s by 6.7%-15.6% across 2 years. In contrast, N and P co-addition on average increased R-s, R-a, and R-h by 1.9%, 7.9%, and 2.1% during the experimental period. Though R-s and R-h were significantly correlated with soil temperature, their temperature sensitivities were not significantly changed by fertilization. R-a was predominantly regulated by soil nitrogen availability (NH4+ and NO3-), soil dissolved organic carbon (DOC), and enzyme activities, while the variation in R-h was mainly attributable to changes in soil microbial community composition and soil beta-D-Cellubiosidase (CB) and beta-Xylosidase (XYL) activities. Conclusion Our findings highlight the contrasting responses of R-s and its components to N or P addition against N and P co-addition, which should be differentially considered in biogeochemical models in order to improve prediction of forest carbon dynamics in the context of N and P enrichment in terrestrial ecosystems. |
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