The Influence Of Vegetation Restoration On Distribution Of Soil Water Stable Aggregate And The Pool Of Carbon And Nitrogen In Loess Plateau

Vegetation restoration is an important factor of soil erosion controlling, what's more important to improve soil quality and fertility by native or man built vegetation restoration in eroded hillslope. According to the belt distribution rule of yellow soil, we chose 5 counties distributed in Shan Xi province as sampling areas including ShenMu, SuiDe, YanAn, WuQi, YiChuan. We studied the relationships among soil organic carbon, available nitrogen storage, the distribution of soil aggregate and aggregate organic carbon content, the same with vegetation type and restoration time. We estimated the influence on soil total organic carbon and aggregate organic carbon by vegetation restoration and discussed the transformation mechanism of the aggregate size and organic carbon after vegetation restoration. The results as follow:(1) The character of carbon and nitrogen store, the distribution of soil aggregates and the aggregate SOC by different types vegetation restoration.Compared with the farmland, vegetation restoration improved SOC, AN and TN storage, total aggregate amount and aggregate SOC content. Vegetations show different restoration effects in the following order : grass > shrub > tree. We found that the vegetation restoration has improved the macro-aggregate amount, influenced the redistribution of particle-sizes fraction of aggregates and improved soil structure and the soil anti-erodibility. We took use of the physical character of aggregate beyond 0.25mm dia. and mean weight diameter (MWD) to estimate soil water-stable aggregate. Results show that vegetation restoration improved the aggregate content with macro-aggregate and effected the redistribution of aggregates in different particle-size fraction. Also the vegetation restoration reformed the soil structure and the soil anti-erodibility. Vegetation restoration didn't show any significant effect on soil silty and clay(<53μm). For all the particle-size fraction, the SOC mostly stored in small macro-aggregate (250-2000μm), then large macro-aggregate( >2000μm) and mciro-aggregate (53-250μm) follows. The lowest SOC content was in soil silty and clay(<53μm).(2) The influence of SOC, AN and TN store and distribution of water stable aggregate on restoration time:Tthe restoration time is another factor on SOC, AN and TN store. We found that the SOC, AN and TN store keeps increasing with the restoration time accumulation. But we also found that the SOC, AN and TN store in the soil which plant acacia for 21 years are lower than in the soil which plant Seabuckthorn for 16 years. It shows that the restoration time is not the main factor. Restoration time has a little effect on soil water stable aggregate distribution but litter on aggregates amount on. It also improved the aggregate (>250μm) amount, increase the soil anti-erodbility.(3) How the region character took effects on SOC , AN and TN store with vegetation restoration:With the reducibility of the latitude, the SOC, AN and TN store and the effects of vegetation restoration on soil properties is increased in Loess Plateau. This phenomena dues to the soil type changing and the soil quality mending, the same with the increase of air temperate and rainfall. WuQi has the lowest SOC, AN and TN store for it's position and climate.