施用秸秆增强茶园土壤团聚化的AM真菌促进机制研究

Straw application can improve the soil structure and fertility in the tea plantations, but the mechanisms of straw application to promote soil aggregation in tea plantations, especially the role of AM fungi in the process is still unclear. The project aims to focus on the role of AM fungi in promoting soil aggregation enhanced by straw application in tea plantations based on the plantations in southern of Henan. Firstly, soil samples are collected from the tea plantations with/without long-term straw application, and the community structures of AM fungi are measured by high-throughput sequencing technology, and the indices of abundance and glomalin-related soil protein (GRSP) content of AM fungi are measured, as well as the soil physical and chemical properties. Then the response of AM to straw application are discussed. Secondly, the dynamic sampling experiment with different amounts of straw application in the tea plantation is assigned. The dynamic variation of AM fungi and soil aggregates in the tea plantation are cleared by analysing the AM fungal indices and the soil aggregates indices, including the particle size compositions and stability. Thirdly, the pot experiment of tea seedlings is carried out with the indigenous AM fungi in the tea plantation. The effect of AM fungi on the soil aggregates variation with/without straw apllication is figured out by resolving the contributions of AM fungi, soil physical-chemical properties and roots of tea seedlings to soil aggregation, and then the promoting mechanisms of AM fungi in soil aggregation with straw application in tea plantations are revealed. The results will provide scientific basis for the soil management in tea plantations and the function performance of AM fungi.

施用秸秆可改善土壤结构和提高土壤肥力，但目前关于施用秸秆促进茶园土壤团聚化的机制特别是丛枝菌根（arbuscular mycorrhizal，AM）真菌所发挥的作用尚不明确。本项目拟以豫南茶园为试验平台，开展施用秸秆增强土壤团聚化的AM真菌促进机制研究。首先从长期施和不施秸秆的茶园采集土样，利用高通量测序等技术测定AM真菌群落结构、种群丰度、球囊霉素相关土壤蛋白含量及土壤理化性质，探讨AM真菌的响应规律。然后布置不同秸秆施用量试验，通过动态采样分析AM真菌、团聚体粒径组成和稳定性等指标，明确茶园土壤AM真菌和团聚体的动态变化。最后利用茶园土著AM真菌布置盆栽试验，通过解析AM真菌、土壤理化性质和茶苗根系等对土壤团聚化的贡献，阐明施或不施秸秆条件下接种AM真菌对土壤团聚体变化的影响，最终揭示施用秸秆条件下AM真菌对土壤团聚化的促进机制。本研究可为茶园土壤管理和AM真菌功能发挥提供科学依据。

茶园土壤存在有机质含量低及结构差等问题，施用秸秆可有效改善这些问题；丛枝菌根（arbuscular mycorrhizal，AM）真菌在土壤结构改良过程中也发挥重要作用。作为土壤结构基本构成单元，团聚体的构成及稳定性可很好反映土壤结构特征和肥力；但施用秸秆在改良茶园土壤结构过程中，AM真菌对茶园土壤团聚化的作用机制尚未明确。因此揭示施用秸秆条件下AM真菌对土壤团聚化的促进机制，不仅可明晰施用秸秆增强茶园土壤团聚化的作用过程，也可为茶园中科学施用秸秆和AM真菌的应用提供理论指导和数据支持。.通过调查施与不施秸秆茶园，发现施用秸秆可明显增加茶树根系AM真菌侵染率（AMC）和孢子密度（spore density，SD）、球囊霉素土壤相关蛋白（glomalin-related soil protein，GRSP）以及土壤团聚体稳定性；通过高通量测序结果发现，Glomeraceae和Calroideoglomeraceae为茶园土壤AM真菌的优势菌群；通过冗余分析进一步发现，AM真菌指标主要受Ca、Al等元素含量以及速效P等土壤营养成分影响。通过在坡地和平地种植茶园布置不同秸秆施用量下的动态采样试验，发现茶园土壤AM真菌富集OTUs种类数量随着时间延长有明显增加；坡地茶园土壤团聚化水平呈现先升后降趋势，而平地茶园具有相反趋势。与不施秸秆相比，不同时间段施用秸秆均对茶园AM真菌及土壤团聚化有明显影响，其中坡地茶园施用大量秸秆影响效果更好，而平地茶园施用少量秸秆即可有较好效果。通过AM真菌和土壤团聚化的关联性分析，初步筛选了AM真菌促进土壤团聚化的路径。紧接着通过冗余分析和实际种群分析发现了施用秸秆条件下茶园土壤团聚化的主要驱动因子。通过构建结构方程模型，分析发现，坡地茶园中AM真菌主要通过GRSP和SD促进土壤团聚体稳定性，平地茶园中则是注意通过SD和AMC来影响土壤团聚体稳定性。