摘要:全球变化会引起凋落物质量和数量的变化以及氮沉降增加，从而影响土壤养分循环。土壤生态酶化学计量可以揭示微生物生长和代谢过程的养分限制，但目前温带混交林土壤生态酶化学计量对凋落物输入和氮添加同时改变的响应还不清楚。通过凋落物处理和氮添加实验设计，探讨温带松栎混交林生态酶化学计量的响应以及影响生态酶化学计量的主要因子。结果表明：（1）凋落物处理和氮添加无显著交互作用，土壤生态酶化学计量在氮添加处理下差异不显著，在凋落物处理下差异显著，表现为叶凋落物加倍（L）和混合凋落物加倍（LB）处理高于枝果凋落物加倍（B）和去除凋落物处理（N）。不同凋落物和氮添加处理下，土壤生态酶化学计量均未明显偏离1：1：1的关系。（2）土壤微生物碳利用效率（CUE_C：N和CUE_C：P）表现为叶凋落物加倍和混合凋落物加倍处理低于枝果凋落物加倍和去除凋落物处理，在氮添加处理下差异不显著。土壤微生物氮利用效率（NUE_N：C）和微生物磷利用效率（PUE_P：C）在不同凋落物和氮添加处理下差异均不显著。TER_C：N在不同凋落物和氮添加处理下差异均不显著，TER_C：P表现为叶凋落物加倍和混合凋落物加倍处理高于枝果凋落物加倍和去除凋落物处理。（3）RDA分析表明土壤pH是影响土壤胞外酶活性和生态酶化学计量的主要因子。研究表明：凋落物的质和量对松栎混交林土壤生态酶化学计量的影响较氮添加显著，可能氮添加对森林土壤微生物的作用机制并非一个瞬间或简单的过程。凋落物的质和量会改变土壤养分状况，而微生物会通过调节生态酶化学计量和养分利用效率对养分变异做出响应，叶凋落物的输入相对缓解了P的限制。凋落物处理和氮添加下土壤的非生物因子比生物因子更能影响土壤胞外酶活性和生态酶化学计量。研究可为土壤微生物对全球变化的响应提供理论依据。



Abstract:Global changes affect the quality and quantity of litter as well as increased nitrogen deposition, which impact the soil nutrient cycling significantly. Soil ecoenzymatic stoichiometry can reveal the limit of nutrients in microbial growth and metabolism. However, it is still unclear how soil ecoenzymatic stoichiometry responds to the synchronous changes in litter input and nitrogen addition in a mixed temperate forest. This study attempts to explore the effects of litter manipulation and nitrogen addition on soil ecoenzymatic stoichiometry and the major influencing factors in a mixed pine and oak. The results showed that (1) there was no significant interactions between litter manipulation and nitrogen addition. Nitrogen addition was no significant difference on soil ecoenzymatic stoichiometry, while the difference was significant under the litter manipulation, which showed that leaf litter double (L) and mixed litter double (LB) were higher than the fine woody litter double (B) and litter removal (N). Soil ecoenzymatic stoichiometry ratios were not significantly deviated 1：1：1 under litter manipulation and nitrogen addition. (2) Soil microbial carbon use efficiency (CUE_C：N and CUE_C：P) under leaf litter double and mixed litter double treatment was significantly lower than that under fine woody litter double and litter removal treatment, but there no significant differences under nitrogen addition treatment. Soil microbial nitrogen utilization efficiency (NUE_N：C) and microbial phosphorus utilization efficiency (PUE_P：C) were no significant differences under litter manipulation and nitrogen addition. TER_C：N was no significant difference under litter manipulation and nitrogen addition. TER_C：P under leaf litter double and mixed litter double treatment was significantly higher than fine woody litter double and litter removal treatment. (3) RDA analysis showed that soil pH was the main factor affecting soil extracellular enzyme activity and ecoenzymatic stoichiometry. The results showed that the quality and quantity of litters had more significant effects on the soil ecoenzymatic stoichiometry than the addition of nitrogen. It is possible that the forest soil microorganisms of mechanism responding to nitrogen addition is not an instantaneous or simple process. The quality and quantity of litters will change the soil nutrient status, and microorganisms will respond to nutrient variation through ecoenzymatic stoichiometry and nutrient utilization efficiency, the input of leaf litter relatively alleviates the limitation of P. It was found that the abiotic factors had more effects on soil extracellular enzyme activity and ecoenzymatic stoichiometry than biological factors under litter manipulation and nitrogen addition. This study can provide a theoretical basis for the response of soil microorganisms to global change.





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