| Vegetation restoration is an important measure to prevent soil erosion and construct ecological environment on red eroded soil in the southern area.To clarify the interactions and evolution mechanism among vegetation, soil and water,this article selected three typical models of vegetation restoration,i.e.Pinus massoniana forest, Schima superba-Pinus massoniana mixed forest and broad-leaved forest.Based on field investigations and lab assays, the content changes and distribution characteristics of total organic carbon, active organic carbon & aggregate organic carbon, and “soil reservoirâ€capacity in 0-60 cm soil layer were determined after vegetation restoration in degraded red soil. Furthermore, the relationship between soil organic carbon pools and soil reservoir capacity was also discussed.The main conclusions are shown as following:( 1) The variation ranges of soil total organic carbon content and organic carbon storage in the whole soil section were 6.20-9.22g?kg-1 and 57.94-87.17t?hm-2 respectively under different kinds of vegetation restoration models.The order of both in the same layers were Pinus massoniana forest > Schima superba-Pinus massoniana mixed forest >broad-leaved forest. With the increase of soil depth, soil total organic carbon content and organic carbon storage were declining. The variation ranges of soil ROC content was0.92-9.17g?kg-1 in different soil layers under all kinds of vegetation restoration models.DOC content range was 535.89-800.46 mg?kg-1, MBC content range was27.24-261.31mg?kg-1.The active organic carbon was declining with the increase of soil depth, the highest organic carbon content was in 0-10 cm soil layer, and they have the phenomenon of surface gathering. The allocation proportion of soil active organic carbon in broad-leaved forest was generally highest. ROC/TOC in broad-leaved forest reached65.5% in 0-10 cm soil layer, and it was far higher than other models. It suggested that broad-leaved forest could improve the activity of soil organic carbon, be propitious to the accumulation of active organic carbon, and supply more effective carbon to organism.(2)Under all kinds of vegetation restoration models,the proportion of > 2mm particle size of soil aggregate content by dry sieve method was the largest, overring 60%, while that of < 0.05 mm particle size by wet sieve method was dominant. The order of broken rate of soil aggregate structure under different vegetation restoration models was broad-leaved forest(53.38%-84.27%) > Schima superba-Pinus massoniana mixed forest(52.22%-70.86%) > Pinus massoniana forest(22.70%-47.83%), which showed that the soil stability degree in Pinus massoniana forest was higher than that in other two models.Soil aggregate organic carbon content was generally higher by dry sieve method than that by wet sieve method under different vegetation restoration models, and the soil aggregate organic carbon content in Pinus massoniana forest was the highest; With the increase ofsoil depth, soil aggregate organic carbon content decreases gradually. With the reduction of particle size of soil aggregate,the trend of soil aggregate organic carbon storage in the same soil layer by dry sieve method under all kinds of vegetation restoration models was first to decrease and then increase and then decrease; while that by wet sieve method was first to decrease and then increase and then decrease and then increase or first to increase and then decrease and then increase. The correlation analysis of soil total organic carbon and aggregate organic carbon showed that the increase of soil aggregate organic carbon in different soil layers had different effects on the accumulation of total organic carbon.(3)Utilizable capacity accounted for the highest proportion of the total capacity of soil reservoir under all kinds of vegetation restoration models, which was 63.47%-70.09%.With the increase of soil depth, the total capacity, utilizable capacity and maximum effective capacity appeared a downward trend, and the decrease in Pinus massoniana forest was minimum. The dead capacity appeared a rising trend, while the trend of flood control capacity was not obvious. Under the comprehensive capacity index of soil reservoir,water storage capacity in Pinus massoniana forest was slightly better.( 4) The related analysis between soil organic carbon density and soil reservoir capacity in 0-60 cm soil layer was made by using canonical correlation analysis model. The results showed that the soil organic carbon levels had an obvious effect on the increase of soil reservoir capacity, and DOC played the dominant contribution in organic carbon levels.While soil organic carbon levels increased by 1%, utilizable capacity and dead capacity would increase by 0.78% and 0.72% respectively.To sum up: soil organic carbon had a significant impact on the improvement of "soil reservoir" function in degraded red soil. We could increase the soil reservoir capacity by increasing soil organic carbon content, especially the active organic carbon content. In this study, Pinus massoniana forest appeared larger capacity, due to its high productivity and high organic carbon density. Therefore, to increase the active soil organic carbon content,raise soil reservoir capacity, enhance the soil capacity of water holding,water storage and water supply, we could develop close planting and stereo planting appropriately, improve land productivity and soil carbon density, and after-culture broad-leaved species in coniferous forest such as Pinus massoniana pioneer tree species at the early stage of vegetation restoration in degraded red soil area,which were of important practical significance to effectivly prevent and control serious soil erosion, fastly recover ecosystems and prevent seasonal drought. |
