AM真菌对红壤团聚体稳定性及其抗蚀能力的影响机制

Soil microbes drive soil aggregate formation and stabilization, play key roles in improving soil resistance to erosion. Arbuscular mycorrhizal (AM) fungi are closely involved in soil aggregate stabilization. However, the impacts of AM fungi on soil aggregate surface structure, pore structure features and soil resistance to water erosion are unclear. The project plans to collect soil samples from eroded red soil area with vegetation restoration. Initially, Illumina Miseq sequencing and AM fungal spore morphological identification are employed to characterize the AM fungi communities in soil aggregates of different sizes. The hyphal distribution in soil aggregates and hyphal structural traits, and soil aggregate stability will be analyzed to sort the key AM fungi community maintaining the soil aggregates stability. Second, a greenhouse study will be conducted using root-hyphae compartment approach and key AM fungi. Environmental scanning electron microscope and synchrontron-based X-ray micro-computed tomography will be used to observe the surface structure and aggregate pore characteristics, aiming to decipher the mechanism of key AM fungi stabilizing soil aggregates. Last, the micro-plots and rain-simulated experiment will be carried out to investigate the effect of AM fungi on the runoff and sediment generation, in order to determine the influence of AM fungi on soil aggregate stability and soil resistance to water erosion. The results will be of great significance in clarifying the mechanisms underlying AM fungi influencing soil aggregate stability, and lay the foundation for utilizing soil microbes to enhance the efficiency of plant measures to conserve soil and water.

土壤微生物是团聚体形成和稳定的驱动力，是提高土壤抗蚀能力的关键因素。AM真菌在团聚体的稳定过程中发挥重要作用，但AM真菌对团聚体表面结构特征、孔隙结构特征和土壤抗蚀能力的影响机制尚不清楚。本项目拟选择红壤侵蚀地水保植物修复区，采用高通量测序和孢子形态鉴定，结合各粒径团聚体中AM真菌菌丝分布、结构特征和团聚体稳定性分析，确定维持团聚体稳定性的关键AM真菌群落；选择关键AM真菌进行分室培养试验，利用扫描电镜和同步辐射CT扫描技术观察团聚体表面结构和孔隙特征，分析AM真菌影响土壤团聚体稳定性的微观机制；采用微小区试验和人工模拟降雨试验监测AM真菌对土壤产流产沙规律的作用，研究AM真菌对土壤团聚体稳定性能和抗蚀能力的影响。本项目对阐明微生物影响土壤团聚体稳定性的机制有重要意义，为合理高效利用土壤微生物强化水土保持植物措施效益提供理论基础。

土壤微生物与土壤结构形成、稳定和功能密不可分，其中的AM真菌更是在土壤团聚体的形成和稳定过程中发挥重要作用，但AM真菌与土壤侵蚀之间的关系尚不明确。本项目解析了AM真菌在红壤团聚体内的分布特征，发现Glomus是红壤团聚体内的优势属；不同粒径团聚体的AM真菌群落组成相似，但多样性随粒径降低而增加，这与不同粒径团聚体内养分含量差异有关。土壤细菌群落多样性随水土流失治理年限增加而增加，治理区土壤真菌和细菌群落组成与未治理对照和次生林差异显著，且朝着次生林方向演替，随治理年限增加不断提高的土壤肥力驱动微生物群落变化，且真菌营养型随治理年限延长从腐生型向共生性转变。AM真菌可通过促进白三叶、百喜草、狗牙根和雀稗地上部生长，提高植被覆盖效率；AM真菌同时可促进这4种草本根系发育，增加水稳性大团聚体含量，且AM真菌对白三叶的促生效果最优。水流冲刷试验表明，AM真菌对紫云英、百脉根、结缕草和狗牙根构建草沟的径流量无显著影响；但AM真菌显著抑制了侵蚀沟发育，通过降低径流功率显著降低了产沙量，在侵蚀控制方面具有显著贡献。