应用生态酶化学计量探索外源氮磷输入对若尔盖泥炭地土壤碳的影响及其机理

Peatlands store approximately 20-30% of all soil carbon (C) in terrestrial ecosystems, and thus soil C accumulation in or loss from peatlands is significant for global climate change. Along with the development of human activities, pollutants such as nitrogen (N) and phosphorus (P), have been frequently discharged into peatlands, and already affected soil C cycling. However, it is unclear to what extent and how the input of N and P influences soil C storage in peatlands. In allusion to the above-mentioned problem, we choose Zoige peatland - the largest peatland in China as the study site, and use ecoenzymatic stoichiometry (ratio of C-, N- and P-related hydrolase activity) to explore the impact of N and P input on soil C storage for the first time. According to the indicating function of ecoenzymatic stoichiometry for microbial C, N and P limitation, we can predict the change of soil C storage by N and P input in peatland. Meanwhile, we combine the alteration of microbial abundance and community to further study how N and P input influences peatland soil C storage. Based on these studies, we may examine if it is feasible for ecoenzymatic stoichiometry to predict the change of soil C as an indicator. This project can not only reveal the dynamics of microbial C, N and P limitation, and also can provide a reliable theoretical basis for predicting the fluctuation of soil C storage under the pollution of N and P in Zoige peatland. Moreover, it has a great significance for protecting global pleatland C storage and mitigating climate change.

泥炭地土壤C含量高达陆地土壤总C的20-30%，因此，其土壤C的积累或释放对全球气候变化具有重大的意义。随着人类活动的影响，外源NP等污染物频繁进入到泥炭地中，并对土壤C循环产生影响，但其影响程度及其影响机制目前仍不清楚。针对上述问题，本项目以我国最大的泥炭地-若尔盖泥炭地为研究对象，首次应用生态酶化学计量(与CNP分解相关的生态酶的相对活性)对土壤微生物CNP限制的指示作用，探索外源NP输入对土壤C储量的影响。同时，结合微生物量及群落结构的变化，深入研究外源NP输入对泥炭地土壤C储量的影响机制，并进一步检验生态酶化学计量作为预测土壤C变化指标的可行性。本项目的科学意义在于揭示泥炭地土壤微生物CNP限制的动态规律，并为准确预测若尔盖泥炭地NP污染对土壤C储量的影响提供可靠的理论依据与基础数据。此外，本项目对保护全球泥炭地C储量及减缓气候变化亦具有重要的意义。

泥炭地土壤碳（C）含量高达陆地土壤总C的20-30%，因此，其土壤C的积累或释放对全球气候变化具有重大的意义。随着人类活动的影响，外源氮磷（NP）等污染物频繁进入到泥炭地中，并对土壤C循环产生影响，但其影响程度及其影响机制目前仍不清楚。针对上述问题，本项目以我国最大的泥炭地-若尔盖泥炭地为研究对象，应用生态酶化学计量(与CNP分解相关的生态酶的相对活性)对土壤微生物CNP限制的指示作用，探索外源NP输入对土壤C储量的影响。同时，结合微生物量及群落结构的变化，深入研究外源NP输入对泥炭地土壤C储量的影响机制。通过本项目的实施，得到结论如下：（1）若尔盖泥炭地土壤理化性质、生态酶活性、微生物群落结构具有明显的时空差异；（2）根据土壤C:N:P化学计量比发现，若尔盖泥炭地土壤微生物为N限制；（3）根据生态酶C:N:P化学计量比，该研究区域土壤微生物为P限制；（4）外源N输入增加了土壤有机碳（SOC）含量、降低了溶解性有机碳（DOC）浓度以及CO2排放量；（5）外源P输入增加了DOC浓度和CO2排放量，并在一定P添加浓度降低了SOC含量。同时，研究发现获取N相关的水解酶活性与土壤C变化密切相关，并根据微生物生长策略推测若尔盖泥炭土壤或为N限制。在N限制状态下，微生物为获取足够的N，产生相应的酶，进而分解土壤有机质，影响若尔盖土壤C循环。因此，外源N输入泥炭地土壤可能会促进土壤C储存，而外源P输入可能会加剧N限制，从而导致C丢失。本项目对保护全球泥炭地C储量及减缓气候变化亦具有重要的意义。