青藏高原高寒草地土壤有机碳滞留时间和温度敏感性研究--反演分析

Soil carbon cycle of grassland ecosystem in the Tibetan Plateau has become the research focus of global climate change. Model is an important tool for studying the terrestrial ecosystem carbon cycle. However, uncertainties exist regarding to the terrestrial carbon cycling due to the poor constrained parameters (such as residence time and temperatrue sensitivity) for soil organic carbon decomposition. Inverse analysis is an approach to estimate the key model parameters, and improve the model simulation accuracy. In this study, we proposed to develop an inverse analysis approach to analyze the temperature sensitivity of different carbon pools, and then analyze the data from long-term incubation experiments. Soil organic carbon residence time and temperature sensitivity of different pools will be estimated by inverse analysis approach in the grassland ecosystem of the Tibetan Plateau. Soil physical and chemical properties, as well as microbial characteries will be investigated to explore the factors and mechanisms that influence soil organic carbon residence time and temperature sensitivity in the Tibetan Plateau. The results will be helpful to accurately estimate the carbon source/sink of the Tibetan Plateau grassland ecosystem, which will be significant for understanding the feedbacks between carbon cycling and global climate change, and for supplying scientific information for the rational use of grassland resources. In additon, this research can provide a new method to accurately estimate terrestrial ecosystem carbon source/sink.

青藏高原草地土壤碳循环是全球变化研究热点。模型方法是陆地生态系统碳循环研究不可或缺的方法，但是由于对土壤有机碳分解的关键参数（如有机碳滞留时间及其温度敏感性）尚不能准确量化，采用模型对生态系统碳循环的研究还存在很大的不确定性。反演分析法可以对研究中难以获得的参数进行估计,提高模型模拟的准确性。本项目将室内土壤有机碳矿化长期培养实验和反演分析法相结合，构建有机碳各组分温度敏感性的反演分析方法，系统地研究青藏高原草地土壤有机碳各组分的滞留时间和温度敏感性，并通过研究土壤理化性质和微生物特征的变化，探讨对土壤有机碳滞留时间和温度敏感性的影响因素和机制。研究结果将为精确估算全球气候变化下青藏高原草地碳源汇，理解土壤碳循环和气候变化间反馈作用以及草地资源的合理利用提供科学依据；同时也为陆地生态系统碳源汇的准确估算提供新方法。

本研究选取青海省海北藏族自治州垂穗披碱草高寒草原（AS-E）、针茅高寒草原（AS-S）、矮嵩草高寒草甸（AM-KH）和藏嵩草高寒草甸（AM-KT）四种植被类型为研究对象，通过构建有机碳各组分温度敏感性的反演分析方法，结合室内土壤有机碳矿化长期培养试验以及各植被类型的土壤理化性状和微生物性状分析，系统研究土壤有机碳各组分滞留时间和温度敏感性，并探讨其影响因素和机制。研究结果表明：1）372天矿化培养结束后，藏嵩草高寒草甸累计矿化量最高，为110.89 mg g-1 SOC，其次为针茅高寒草原和垂穗披碱草高寒草原，矮嵩草高寒草甸矿化量最低，为43.04 mg g-1 SOC。总有机碳库针茅高寒草原分解率最高为8.32%，矮嵩草高寒草甸分解率最低为4.22%。2）土壤活性有机碳库滞留时间在三个土层均为AM-KT最低，0-10 cm土层AS-S最高，10-20和20-30 cm土层均为AS-E最高。慢性土壤有机碳库滞留时间0-10 和20-30 cm土层为AM-KH > AS-E > AS-S > AM-KT, 在10-20 cm 土层为AM-KH > AS-S > AS-E > AM-KT。3）土壤活性碳库温度敏感性三个土层的均值高寒草甸样地最高，AM-KH和AM-KT分别为1.97和1.87，两高寒草原相差不大，AS-E和AS-S分别为1.75和1.74；慢性碳库温度敏感性AS-S样地最高，为4.79，其次为AM-KH样地，AS-E和AM-KT样地最低。4）土壤活性碳库滞留时间和土壤粘粒组分含量呈正相关性，与土壤微生物熵呈显著负相关性；土壤慢性碳库滞留时间和土壤粘粒组分含量以及C:N有显著正相关性，与pH和土壤微生物熵具有显著负相关性。结构方程模型结果表明，活性碳库滞留时间主要受到土壤微生物熵影响，土壤粘粒含量对其间接影响；慢性碳库滞留时间主要受到土壤微生物熵和pH的直接影响，受到土壤粘粒含量间接影响。