The Study Of Characteristics Of Soil Organic Carbon And Aggregates In Diffferent Degraded Alpine Meadow

Terrestrial ecosystems as an important part of the global carbon cycle, play a key role in the global carbon balance of payments, while the grassland ecosystem is one of the main type of the world’s terrestrial ecosystems, more than half of the grass organic carbon distribution in China is in alpine grassland soil. Aggregate is considered as a substituted index of the stability of soil structure, and the mechanisms of SOC stabilization are associated with capacity of SOC sequestration. the studies in this field will help the governments make efficient policies to increase SOC. Qinghai-Tibet Plateau, known as the promoter region of the world’s greenhouse gas, is the widely distributed area of alpine meadow, alpine meadow soil is one of the important soil organic carbon pools, but due to the expansion of degradation degree in alpine meadow, soil will increase the risk of carbon loss. Therefore, maintain the stability of the soil carbon pool in the alpine meadow for the mitigation of climate change has great significance.According to the mountain slope positions, the studied profile soil and (0-10cm) top-soil soil were sampled from representative alpine meadow soils in Three Rivers region of the Tibetan Plateau. Undisturbed top-soil samples were separated to different size aggregates by low-energy ultra-sonic dispersion procedure. Soil aggregates, variation of SOC and SOC distribution in aggregates were analyzed to illuminate the effects on aggregates stability and SOC reserves in different degraded alpine meadow. The contents of rearch are as follows:1) the change of soil organic carbon and soil active carbon(LOC, POC) in different degraded grassland to illuminate difference of compose and proportion of soil organic carbon.2) the change of aggregates distribution and distribution of SOC in aggregares in different degraded grassland to illuminate the relationship between grassland soil organic carbon and aggregates.3) the change of stability of soil aggregates in different degraded grassland to illuminate the organic carbon physical protecting in aggregates.The main findings are as follows:1) Average soil carbon density of Alpine meadow was8.26kg·m-2on Yema Shoal, which was at a high level in all types of soil in China. The SOC content decreased with soil depth, and tended to surface enrichment in alpine meadow, the profile distribution of SOC in0-50cm was affected by the different degradation, the SOC content in0-50cm decreased with the expansion of degradation degree. It had positive liner relation between the content of SOC and LOC, SOC and POC.LOC and POC content of (0-10cm) soil decreased with the expansion of degradation degree, while LOC/SOC was highest in heavily degraded grassland, indicating that the instability of the soil organic carbon decreased with the expansion of degradation degree.2) Among those surface soil (0-10cm) aggregates of alpine meadow,2000～200μm and200～20μm occupied the most, the proportion of2000～200μm aggregates decreased and formation of macroaggregates weakened with the expansion of degradation degree. The content of organic carbon in aggregates were higher in the2000-200μm and<2μm, but the contribution of2000～200μm for the whole soil decreased with the expansion of degradation degree, while <2μm was an increasing trend. The content of SOC in aggregates were un-degradation>lightly degraded and moderately degraded>heavily degraded, except<2μm aggregates group. The protective effects of aggregates on soil organic carbon reduced with the expansion of degradation degree.3) The soil aggregates stability of alpine meadow reduced with the expansion of degradation degree, indicating that grassland degradation weakened the protective effects of aggregates on soil organic carbon,and therefore, we should strengthen the protection of the soil carbon pool of alpine meadow at land use expansion areas.