Thermal Stability Analysis Of Soil Organic Matter Under The Background Of Land Use Change In Huanjiang Karst Area Of Guangxi

The quantity and stability of soil organic matter?SOM?is susceptible to changes in land use,and thermal analysis techniques are an effective method for quantifying the quantity and stability of SOM.In this paper,thermal analysis techniques,including thermogravimetric analysis and differential scanning calorimetry,are used to study the effects of land use change on the thermal stability of SOM under different land use types?vegetation destruction and vegetation restoration?,in Jinqiao Village,Da'an Township,Huanjiang,Guangxi.Four indicators are used to illustrate the stability of SOM,which are%Exo₁?proportion of labile SOM?,TG-T₅₀?corresponding temperature when SOM mass is reduced by half?,DSC-T₅₀?corresponding temperature when half of energy is released during SOM combustion?,ED?energy density?,respectively.Explored the thermal stability of bulk soil?>2 mm?and different soil size fractions?>53?m?,?53-20?m?,?20-2?m?,?<2?m?in surface layer?0-20 cm?.Vegetation destruction is conver nature forest into eucalyptus forest?EF?,grassland?UG?,and corn field?CF?.Vegetation restoration is restored the corn field?CF?to eucalyptus forest?CF to EF?and unused grassland?CF to UG?.The main findings are as follows:1.For vegetation failure mode:the soil organic carbon?SOC?total nitrogen?TN?concentration is significantly reduced after converting the original forest into eucalyptus forest,grassland and cornfield;the proportion of active SOM in the wasteland and cornfield soil is reduced.The stability is increased,and the increased stability of SOM in maize indicates that the active SOM is consumed by the human activities such as farming,and the inert SOM is accumulated,resulting in higher thermal stability of the whole soil SOM;the conversion of the original forest into the eucalyptus forest and The two artificial ecosystems of cornfield resulted in a decrease in SOM stability in coarse powder?53-20?m?and cosmid?<2?m?,thus indicating that human disturbance has already stabilized SOM in small particle size soil particles.A change has occurred.2.For vegetation restoration mode:the SOC and TN concentrations in the soil increased significantly after the corn land was restored to eucalyptus forest and grassland,especially the SOC concentration in the grassland was doubled,and the SOC and TN concentrations in each grain level were both There is a significant increase;in addition,the stability of SOM in the whole soil and each grain level is significantly improved after the corn land is restored to the grassland,indicating that returning farmland to forests and grasses is beneficial to the recovery of SOC concentration and is beneficial to the stability of SOM.The improvement of sex is conducive to the accumulation and storage of SOC.However,the stability of SOM in whole soil and various grain scales did not change significantly after the corn land was restored to the artificial ecosystem of eucalyptus forest,indicating that human disturbance is not conducive to the accumulation of SOM.Therefore,this study shows that transform from nature forest to artificial ecosystems?eucalyptus forests,corn fields?,reducing the concentration of labile SOM,and the farmland becomes a carbon source;restoring artificial systems such as farmland to natural grassland is not only beneficial to SOM.Accumulate and improve the thermal stability of SOM,making the soil an important carbon sink.