Stability Of Soil Organic Carbon During Different Vegetation Restoration Stages In Degraded Red Soil

Currently,the world is experiencing changes of warming and precipitation patterns.As the largest carbon pool of terrestrial ecosystems,small changes in environmental factors may have significant impacts on soil organic carbon pools and ultimately feedback to global climate change.This study analyzed soil organic carbon stability and its influencing factors of different vegetation restoration stages in degraded red soil,and then further explored the temperature sensitivity of organic carbon mineralization under different water treatments in different substrate soils,which could provid theoretical basis for improving carbon sequestration potential in degraded soils in the context of global change.The typical degraded red soil of Changting County in the mid-subtropical zone was selected as research object.By using space for time substitution method,we selected bare land(B),Pinus massoniana Lamb.(Pinus massoniana)restored ten,twenty and thirty years old plantation(R-10,R-20 and R-30)and natural forest(N),respectively,and the change of soil organic carbon stability and its influencing factors during vegetation restoration were studied.In addition,considering the difference of carbon quality in different vegetation restoration stages,B,R-20 and N soils were chosed as incubation soils.And we set up two soil water treatments,which were thirty percent of field water holding capacity(30% WHC)and 60% WHC,respectively.At the same time,two temperature treatments were set up under each soil water treatment,which were 18? and 28?,respectively.The aims were to study the effect of the main environmental factors on temperature sensitivity of organic carbon mineralization.The results of this work were as follows:(1)Results showed that soil total organic carbon content was expressed as N > R-30 > R-20 > R-10 > B,meanwhile,there were significantly increasing trend of soil labile carbon and passive carbon during the restoration process.However,vegetation restoration decreased the ratios of soil labile carbon to total organic carbon,and increased the ratios of passive carbon to total organic carbon.Those results indicated that vegetation restoration increased soil organic carbon stability.Redundancy analysis also showed that the interpretation rates of soil physical and chemical properties,iron-aluminum oxides,microbial biomasses and enzyme activities on soil organic carbon were 92.3%,81.5%,76.6% and 83.2%(P<0.01),respectively.(2)Soil moisture and temperature significantly affected soil organic carbon mineralization.At the 30% WHC treatment,the amounts of organic carbon mineralization decreased as the order: N > R-20 > B.But,at the 60% WHC treatment,they decreased as the order: R-20 > N > B.In terms of temperature treatments,the amounts of organic carbon mineralization at 28? were significantly higher than at 18?.These results demonstrated that increased temperature promoted soil organic carbon decomposition.Redundancy analysis showed that the interpretation rates of soil C:N and C:P for soil organic carbon mineralization were 82.7% and 73.1%,respectively.In addition,the temperature sensitivity of soil organic carbon mineralization decreased as the order: B > R-20 > N.The results showed that low carbon quality in the B soil was the important reason for the high temperature sensitivity.(3)In general,high temperature and high soil moisture inhibited the microbial biomasses of R-20 and N soils,and there were significant differences in soil microbial biomasses and enzyme activities in different soil substrates.At the same time,soil fungi,gram-positive bacteria and enzyme activities were important factors affecting the temperature sensitivity soil organic carbon mineralization.Overall,vegetation restoration increased the stability of soil organic carbon.In addition,there were significant differences in temperature sensitivity of organic carbon mineralization under different water treatments in different soil substrates,therefore,and the differences in soil organic carbon quality and microbial community are the main reasons for the higher sensitivity of organic carbon mineralization in B soil.