草地凋落物影响土壤有机碳稳定性的生物学机制： 土壤微食物网碳流的调控作用

The soil organic carbon stability is the key to carbon cycle research. Revealing its influence and regulation mechanisms are important parts of understanding the turnover rate of soil organic carbon in global climate change. Litter is an important part of soil organic carbon input. And litter effects on soil organic carbon are strongly controlled by the bidirectional regulation of soil micro-food web between litter and soil organic carbon. But the regulation mechanism is not clear. In this project, Songnen steppe ecosystem will be studied. We will study litter effects on soil micro-food web by examining the soil microorganism and nematode structures and metabolic activities. We will study the effects of litter on soil micro-food web carbon transformation and fixation in grassland by stable isotope techniques method. The structural equation model will be used to quantify the contribution of litter-soil-soil micro-food web on the stability of soil organic carbon pool. This study will figure out the biological mechanism of litter input on the stability of soil organic carbon pool in Songnen steppe. Therefore, by giving insight into the mechanism that the litter-soil-soil micro-food web impact on soil organic carbon, this study will enrich our knowledge of soil organic carbon pool stability, and provide the scientific guideline to the global terrestrial carbon cycling.

土壤有机碳库稳定性是碳循环研究的核心，揭示其影响因素和调控机制是认识全球气候变化背景下土壤有机碳分布和周转的重要内容。作为土壤有机碳输入的重要途径，凋落物对土壤有机碳的影响，强烈受制于土壤微食物网对凋落物和土壤有机碳的双向调控作用，但其影响机理尚不明确。本项目选择松嫩平原草地生态系统，从土壤微生物和线虫群落结构和代谢活性角度，研究不同凋落物质量对土壤微食物网的影响；采用稳定同位素技术手段，研究凋落物对土壤微食物网碳转化和固定的影响；利用结构方程模型分析凋落物-土壤-土壤微食物网对区域土壤有机碳库稳定性的贡献。揭示松嫩草地生态系统凋落物输入对土壤有机碳库稳定性的生物学影响机制。本项目将有助于揭示凋落物-土壤-土壤微食物网对土壤有机碳的影响过程及调节机制，对丰富土壤有机碳库稳定性的影响机制、认识全球陆地碳循环过程具有重要科学意义。

凋落物输入是草地生态系统土壤碳的重要来源，但土壤微食物网生态过程是如何影响凋落物对土壤有机碳组分的影响的机理尚不明确。本项目结合野外试验和室内培养试验，利用稳定同位素技术，研究凋落物输入背景下不同退化草地土壤微生物和线虫群落结构对土壤有机碳组分的影响。结果表明：退化草地中凋落物分解能够显著地影响土壤微生物和土壤线虫群落结构。随着退化程度的增加，土壤细菌和土壤线虫群落丰度降低，多样性减少，从而使得土壤微食物网群落结构稳定性降低，更容易受到外界环境的扰动。凋落物分解虽然改变了土壤微生物真菌细菌比，但土壤微食物网仍以细菌分解通道为主。凋落物分解主要影响了退化草地碳组分中的总有机碳和微生物量碳同位素丰度。利用碳同位素构建结构方程模型发现土壤碳组分主要通过影响细菌分解通道影响整个土壤微食物网的。这表明退化草地凋落物的分解，能够影响土壤碳组分，且土壤微食物网在其中起着重要作用。本研究为进一步揭示草地退化的机理提供了理论依据。