土壤微生物群落结构调控太白红杉林凋落物呼吸温度敏感性的机理研究

Studying the changing characteristics of litter respiration temperature sensitivity can provide important parameter support for carbon cycle model. The essence of litter respiration is mineralization and decomposition of litter by soil microorganisms, the complex interactions between soil microorganisms and litter, and the complicated distribution pattern of soil microbial community structure along an altitudinal gradient, which causes the mechanism of soil microbial community structure affecting the temperature sensitivity of litter respiration is more complicated, but the underlying mechanism is not clear. In an alpine timberline of Qinling mountains (larix chinensis), in-situ observation experiment and"undisturbed soil column translocation"experiment were used through the difference of altitudinal gradient, combined with incubation experiment and high-throughput sequencing techniques for analysis the changing characteristics of Larix Chinensis litter respiration temperature sensitivity and soil microbial community structure along an altitudinal gradient, exploring the relationship between soil microbial community structure and temperature sensitivity of Larix Chinensis litter respiration, analyzing the effect of fresh litter inputs and environmental factors on soil microbial community structure and temperature sensitivity of Larix Chinensis litter respiration, and revealing the mechanism of soil microbial community structure influence temperature sensitivity of Larix Chinensis litter respiration, which can provide important data support and theoretical basis for alpine timberline of Qinling mountains responding to climate change. The research results are expected to deepen the understanding of the process and the impact mechanism of carbon cycling on alpine timberline in Qinling mountains.

研究凋落物呼吸温度敏感性的变化特征可以为碳循环模型提供重要的参数支持。凋落物呼吸的本质是土壤微生物对凋落物的矿化分解，土壤微生物与凋落物复杂的交互作用及土壤微生物海拔分布格局的复杂性，导致土壤微生物群落结构影响凋落物呼吸温度敏感性的机理更加复杂，但是其潜在的机理目前尚不清楚。本项目以秦岭太白山的高山林线太白红杉林为研究对象，利用海拔梯度差异开展野外原位观测和"原状土柱易位"试验，结合室内培养试验和高通量测序技术，分析凋落物呼吸温度敏感性和土壤微生物群落结构随海拔梯度的变化规律，探究土壤微生物群落结构与凋落物呼吸温度敏感性之间的内在联系，解析新鲜凋落物量和环境因素对凋落物呼吸温度敏感性和土壤微生物群落结构的影响，揭示土壤微生物群落结构影响凋落物呼吸温度敏感性的机理，为秦岭高山林线应对气候变化提供数据支持和理论依据。研究结果有望深化对秦岭高山林线碳循环过程和影响机理的认识。

土壤呼吸是陆地生态系统碳循环的一个重要组成部分，且凋落物输入会导致土壤呼吸的显著增加，但是土壤微生物调控凋落物输入后土壤呼吸增加的机理尚不明确。本项目通过样品采集、文献收集和借助Meta分析技术，分析土层深度和土壤有机碳储量随海拔的变化规律，探究土壤呼吸响应凋落物输入的变化特征，解析凋落物输入对土壤微生物和底物有效性的影响，揭示土壤微生物调控凋落物输入影响土壤呼吸的机理。结论如下：(1)在秦岭太白山，土壤有机碳储量和土层深度均呈现出随着海拔的增加而减少的趋势，但是单位土层深度上的土壤有机碳储量却呈现出增加的趋势；(2)凋落物输入后导致土壤呼吸显著增加，且呈现出针叶林(51%)>阔叶林(41%)>混交林(32%)的趋势；(3)凋落物输入后导致底物有效性(MBC和DOC)和土壤微生物种群数量(PLFA)分别增加了51%和13%，但是却导致土壤真菌/细菌PLFA比率(群落结构)减少了23%；(4)凋落物输入后土壤呼吸与底物有效性、微生物种群数量和群落结构密切相关(P<0.05)，且对土壤呼吸的贡献呈现出微生物种群数量>微生物群落结构>底物有效性的趋势。因此，凋落物输入后微生物种群数量是导致土壤呼吸增加的重要原因，上述研究结果有望进一步深化对山区碳循环过程和影响机理的认识。