高寒草原、高寒草甸土壤团聚体有机碳与微生物变化及其相互作用

Both alpine steppe and alpine meadow are developed respectively in the cold, droughty and humid conditions in the subfrigid zone in the Qinghai-Tibet Plateau. They are apline grassland types with the most important ecological status and the largest area, and are the most sensitive to environmental changes. In this application, the great attention is paid to matter circulation and interaction with organisms inside of soil, and the exploratory researches are done on two types of grasslands (including normal grassland, light degraded grassland and severely degraded grassland) and artificial adjustment (degradation and restoration) of the grassland status, so as to determine the organic carbon and microorganisms and their changes. At the same time, the soil aggregates organic carbon (SAOC) and constituents (active soil organic carbon, light fraction organic carbon, coarse particulate organic carbon, fine particulate organic carbon, and mineral-associated organic carbon), as well as temporal and spatial changes and changing features of microorganism community structure, activity and functions are ascertained from the macroscopic and microscopic aspects. By this way, the application sets forth the interaction of SAOC and microorganisms in cold droughty and humid conditions as a whole in the plateau, and the impacts of the interaction on stability of grassland soil and its organic carbon. The research results can deepen the research on the dynamic changes of the grassland ecosystem circulation in different extreme environments and understanding of microorganisms' impacts on these changes, and provide new forecast and control thinking for study on alpine grassland environment and its changes.

高寒草原、高寒草甸分别发育于青藏高原亚寒带寒冷干旱、寒冷湿润环境，是西藏面积最大、生态地位最为重要、对环境变化最为敏感的高寒草地类型。本项申请以土壤内部物质循环及其与生物的相互作用为关注点，拟通过对两类草地（均包括正常草地、轻度和严重退化草地）、草地状态人为调节（退化、恢复）的探索性研究，在明确土壤有机碳、土壤微生物及其变化的同时，着重从宏观、微观上分别探明土壤团聚体有机碳（SAOC）及其组分，团聚体内微生物群落结构、活性与功能的时空变化规律和变化特征，进而从整体上阐明高原冷干、冷湿环境中草地SAOC与微生物的相互作用及其差异，以及这一作用对草地土壤和SOC稳定性的影响。研究结果有望深化对不同极端环境下高寒草地生态系统碳循环动态变化及其微生物影响的认识，对高寒草地环境及其变化等亦可能提供新的预测与调控思路。

高寒草原、高寒草甸分别发育于青藏高原亚寒带寒冷干旱、寒冷湿润环境，是西藏面积最大、生态地位最为重要、对环境变化最为敏感的高寒草地类型。为此对藏北高原两类草地（均包括正常草地、轻度和严重退化草地）表层（0~10cm）、亚表层（10~20cm）土壤团聚体有机碳（SAOC）及其组分，团聚体内微生物群落结构、活性与功能等进行了研究。初步明确了两类草地及状态变化与SAOC组分的相互影响、SAOC组分间的相互关系，SAOC对SOC的贡献及与土壤结构变化的关系；初步探明了不同状态高寒草原、高寒草甸土壤团聚体内微生物群落结构与活性的变化特征，土壤中与团聚体内微生物的相互关系；基本掌握了两类草地及其状态变化与土壤微生物的相互影响、关键功能微生物种群的变化特征。研究结果对系统探索高原寒旱环境中AOC的变化特征、变化过程与变化机理，探寻退化高寒草地生态系统预测与调控的新思路等均具重要的科学意义和参考价值。.结果表明，高原冷干、冷湿环境中不同粒级SAOC及其变化受草地退化程度、土层深度、微生物等的深刻影响，主要表现为：（1）不同程度退化草地w（SAOC）均呈下降，轻度、严重退化草地不同粒级w（SAOC）的土层分布特征仍与未退化草地一致，但严重退化草地表层、亚表层w（SAOC）均显著高于轻度退化草地；w（SAOC）的土层差异随草地退化加剧大幅缩小，草地退化缩小了不同土层间SAOC含量的差异，且草地退化程度越高则表层、亚表层间SAOC含量的差异越小。（2）高原冷湿环境中，草地退化导致表层、亚表层SAOC含量均呈下降，且降幅随草地退化加剧均趋于显著提高；草地退化明显缩小了土层间团聚体构成的差异，土壤团聚体与SAOC、SOC与SAOC间的关系受草地退化程度的影响。草地退化程度影响着土壤中、团聚体内MBC、CEA与ALOC的相互关系。（3）3 类微生物数量在不同退化程度高寒草原中均表现出放线菌 ＞ 细菌 ＞ 真菌的特征，放线菌在3种微生物中具绝对优势；随着草地退化的加剧，高寒草原微生物数量在表层和亚表层土壤中的分布逐渐趋于一致，高寒草甸则不然。