Changes in Soil Aggregates Composition Stabilization and Organic Carbon during Deterioration of Alpine Grassland

The stability of alpine grassland ecosystem is closely related to the stability of soil structure. The objectives of this study were to analyze the characteristics of soil aggregates and organic carbon in different degradation stages of alpine grassland in northwest Sichuan, and to build the relationship between soil organic carbon and aggregates. The results showed that the non-degraded grassland was dominated by macro-aggregates (>0.25 mm), while the degraded grassland was dominated by micro-aggregates. Both soil aggregate stability and soil organic carbon content were significantly reduced with the intensification of grassland degradation. The soil organic carbon content in degraded grassland was significantly lower than that in non-degraded grassland, and the fastest decline stages of the soil organic carbon occurred in the transformation processes from non-degraded to lightly degraded. The highest value of the soil aggregate organic carbon appeared in the 0.5-2 mm size, and the organic carbon content of each aggregate also decreased with the grassland degradation. The soil organic carbon and soil aggregate organic carbon were significantly correlated with the stability index of soil aggregate in the process of grassland degradation ( P <0.01).