Abstract: In order to study the characteristics of soil aggregates and plant interspecific affinity along degradation grassland in three rivers region, soil properties and plant community traits were measured in light, moderate, severely and extreme severely degraded grassland. We analyzed fractal dimension, mean weight diameter of soil aggregates, community composition and interspecific association. The results showed that, with the aggravation of degradation, the fractal dimension of soil particles with the same size decreased gradually in the same soil layer. The proportion of soil aggregates with larger than 0.5 mm particle size decreased, but average weight diameter with smaller than 0.5 mm soil particles increased gradually. The distribution of aggregates with different particle sizes was less affected by soil depth. The plant diversity was the highest in moderately degraded grassland with a increase from 27.4% to 64.5%, as well as the most complicated interspecific correlation. Besides, the proportion of positive association species pairs increased, while that of negative pairs decreased. the correlation and properties of species pairs also changed significantly. Obvious soil desertification, changed building species and significantly increased miscellaneous grass was discovered during the degradation process, and the correlation between species pairs tended to be simple, as well that the intensity of interspecific competition decreased gradually. Therefore, interspecific affinity should be maintained to prevent soil desertification and grassland degeneration.

Key words: Three rivers region, Alpine Grassland, Grassland degradation, Soil aggregates, Interspecific affinity

摘要： 为研究三江源地区不同退化程度的高寒草原土壤团聚体和种间亲和性特征，以轻度、中度、重度和极度退化草地为研究对象，对土壤特征和群落特征进行测定。结果表明：随着退化程度的加剧，同一土层相同粒径土壤颗粒的分形维数逐渐减小，>0.5 mm粒径土壤团聚体占比下降、平均重量直径减小，<0.5 mm粒径土壤颗粒的平均重量直径增大，各粒径团聚体分布受土层深度影响较小；中度退化草地物种多样性最高，其种间相关性也最为复杂；随退化程度加剧，正联结种对占比增大，而负联结种对占比下降，种对间的相关性和性质也发生显著变化；退化过程中土壤沙化明显，群落建群种发生变化、杂类草比例显著增加，种对间相关性趋于简单，种间竞争强度逐渐降低。因此，在草地退化过程中维持群落种间亲和性，可有效遏制土壤沙化和草原进一步退化。

关键词: 三江源, 高寒草原, 草地退化, 土壤团聚体, 种间亲和性