青藏高原高寒草甸退化沙化过程及恢复过程中土壤微生物的响应机制

Soil microorganism is the vitally important and most active biotic factor in the soil ecosystem. Since there is no systematic and deep study on the response mechanism of soil microorganism and soil ecosystem evaluation in the degeneration and desertification processes of grassland and the ecosystem restoration process at present, the paper selects the degenerating and desertifying alpine meadow on the eastern edge of the Qinghai-Tibet Plateau as the research platform to study and analyze the vegetation on the ground, soil microbial community, soil nutrients and soil enzyme activity by combining Illumina MiSeq high-throughput sequencing method and Real time PCR together, in order to discuss the changing law of soil microorganism in the degeneration and desertification processes of alpine meadow and reveal the changing characteristics in different degeneration stages and the relationship between soil microorganism and main soil nutrient factors. It also analyzes the characteristic change of soil microorganism of alpine meadow in different ecosystem restoration ways, identify the co-successional law of plants and soil microorganism communities in the grassland restoration process, in order to provide the theoretical basis for making the scientific evaluation of grassland restoration effect and exploring the effective ecosystem restoration way. By combining the research of soil ecological process change in the degeneration and desertification processes of alpine meadow and in the ecosystem restoration process on the Qinghai-Tibet Plateau, it provide the theoretical basis for fully realizing the soil ecosystem evaluation in the degeneration and restoration processes of grassland.

土壤微生物是土壤生态系统中极其重要和最为活跃的生物因子。针对目前草地退化沙化过程及生态恢复过程中土壤微生物的响应机制与土壤生态系统评价缺乏系统深入的研究，本研究选取青藏高原东缘退化沙化高寒草甸作为研究平台，采用了Illumina MiSeq高通量测序法和Real time PCR相结合的方法，通过对地上植被、土壤微生物群落、土壤养分及土壤酶活性等进行研究与对比分析，探讨高寒草甸退化沙化过程中土壤微生物的变化规律，揭示不同退化阶段土壤微生物的变化特征及其与主要土壤环境因子的关系；分析不同生态恢复方式下高寒草甸土壤微生物特性变化，认识草地恢复过程中植物和土壤微生物类群的协同演替规律，为科学评价草地生态恢复效果及探索有效生态恢复途径提供理论依据；通过结合对青藏高寒草甸退化沙化过程以及生态恢复过程中土壤生态过程变化的研究，对充分认识草地退化过程和恢复过程的土壤生态系统评价提供理论依据。

开展草原沙化治理及生态恢复的研究，对于开展草原生态保护措施，减少草原沙化损失具有重要的意义。本研究针对目前高寒草甸退化沙化过程以及生态恢复过程，选取青藏高原东缘退化沙化高寒草甸作为研究平台，采用了Illumina MiSeq高通量测序法和Real time PCR相结合的方法，通过对地上植被、土壤微生物群落、土壤养分及土壤酶活性等进行研究与对比分析。主要研究结果如下：(1).围栏禁牧和智慧放牧均提高了大团聚体比例(4.0 and 5.2 times, P < 0.05)，提高了土壤团聚体稳定性；智慧放牧改变了细菌群落结构，增加了细菌数量；团聚体结构和恢复管理模式影响了土壤细菌群落和土壤养分。智慧放牧是青藏高原沙化草甸的更有效的一种恢复管理模式。(2) 在青藏高原草甸沙化过程中，退化至轻度沙化阶段土壤养分、微生物碳氮、土壤水分、pH就发生显著变化，至中度沙化阶段时土壤团聚体稳定性显著降低，至重度及极度沙化阶段时土壤细菌数量和多样性显著降低。在草甸沙化过程中，植被盖度通过影响土壤特性(如pH和SOC)正向影响土壤团聚体稳定性，而FMi和FSC颗粒中的细菌群落与土壤团聚体呈负相关。(3) 沙化草地恢复过程中，LM粒级团聚体百分比总体表现出增多的趋势，土壤 MWD 随恢复时间的增加而增加。各团聚体组分Chao1指数和Shannon指数并未随着草地恢复年限的增加而发生显著变化。草地恢复过程对小团聚体组分微生物群落的影响更显著。本研究首次研究青藏高原草甸土壤沙化过程以及生态恢复过程中土壤团聚体与土壤养分积累和细菌群落之间的变化规律。探讨草地恢复及沙化过程中土壤团聚体、养分及微生物特性变化，是研究草地恢复及沙化过程机理的重要途径，为科学评价草地生态恢复效果及探索有效生态恢复途径提供理论依据。