Effects Of Long-Term Vegetation Restorations On Soil Organic Carbon Accumulation And Mineralization In The Karst Rocky Desertification Ecosystem,SW China

With the increasing concentration of CO₂in the global atmosphere,reducing the source and increasing sink has become a research hotspot at home and abroad.Soil carbon sink has great carbon neutralization potential and plays an important role in the global carbon cycle.Vegetation restoration not only significantly changes the land cover and affects the input and output of soil organic carbon,but also significantly changes the physical and chemical properties of soil and soil enzyme activities,which is bound to significantly affect the soil organic carbon pool.Therefore,it is of great significance to reveal the effects of vegetation restoration on soil organic carbon accumulation and mineralization in order to reduce carbon emissions and increase carbon sequestration.In this study,we selected the soil of seven vegetation restoration measures as the research objects,which are from the rocky desertification area of the Guanling-Zhenfeng Huajiang Karst Plateau Valley in southwest Guizhou,such as imperial bamboo grass（Pennisetum sinese）,amomum（Amomum villosum）,honeysuckle（Lonicera japonica）,chinese prickly ash（Zanthovylum bungeanums）,pitaya（Hylocereus undatus）,cypress-trees（Cupressus funebris）and teak（Tectona grandis）plantation.And the bare land was taken as contrast.We collected the soil samples in the soil layers of 0-5cm,5-10cm and 10-15cm.The distribution and accumulation characteristics of total soil organic carbon and its components（recalcitrant organic carbon,easily oxidized organic carbon,soluble organic carbon and microbial biomass carbon）as well as the characteristics of organic carbon mineralization were studied under different vegetation restoration measures,and the key factors and internal driving mechanism of long-term vegetation restoration affecting soil organic carbon accumulation and mineralization were discussed by using correlation analysis and redundancy analysis.The main research results are as follows:（1）Long-term vegetation restoration has a significant effect on soil organic carbon accumulation in karst rocky desertification.Among the seven restoration measures,the soil organic carbon content and storage of honeysuckle were the largest,37.71 g·kg^-1and 18.72 t·hm^-2,respectively.Soil recalcitant organic carbon contents of cypress-trees and honeysuckle and the content and storage of soil dissloved organic carbon were higher than other vegetation restoration mearsures and the bare.Moreover,the soil recalcitant organic carbon storage of honeysuckle plantation was the largest,which was 12.40 t·hm^-2.However,the content and storage of easily oxidized organic carbon in the imperial bamboo grass and amomum plantation were significantly lower than those in the control plots.The restoration measures of honeysuckle,cypress-trees and teak significantly increased soil organic carbon content and storage,recalcitant organic carbon content and its proportion in total soil organic carbon.The restoration measures of imperial bamboo grass and amomum significantly reduced soil organic carbon content and storage,and significantly increased the proportion of dissloved organic carbon and microbial biomass carbon in soil organic carbon.There was significant correlation between soil organic carbon accumulation and soil enzyme activity and physicochemical properties.（2）Long-term vegetation restoration in karst rocky desertification not only significantly changes the rate of soil organic carbon mineralization,but also significantly affects the temperature sensitivity of soil organic carbon mineralization(Q₁₀).Among the seven restoration measures,the soil organic carbon mineralization rate of teak,cypress-trees and honeysuckle plantation were higher than other vegetation restoration measures and the bare.The soil organic carbon mineralization(Q₁₀)of teak and cypress-trees was significantly lower than other vegetation restoration measures.Vegetation restoration significantly enhanced the soil organic carbon mineralization process and improved the temperature sensitivity of organic carbon mineralization.In addition,the study also found thatβ-1,4-glucosidase,β-1,4-n-acetylglucosaminidase,alkaline phosphatase,Soil moisture content,total nitrogen,total phosphorus,C/N,C/P and soil organic carbon mineralization had a certain significant or extremely significant correlation.However,there was no correlation betweenβ-D-cellobiohydrolase,Leucine Aminopeptidase,Sucrase,p H,bulk density,N/P and soil organic carbon mineralization.（3）There was significant correlation between soil organic carbon accumulation and mineralization.Total soil organic carbon,recalcitrant organic carbon and easily oxidized organic carbon were significantly correlated with soil organic carbon mineralization rate and cumulative mineralization amount（P<0.05）,ROC/TSOC was significantly correlated with organic carbon mineralization rate and cumulative mineralization amount（P<0.01）.However,there was no correlation between dissolved organic carbon and any organic carbon mineralization indicators（mineralization rate,cumulative mineralization amount and cumulative mineralization rate）（P<0.05）.（4）Redundancy analysis results showed that soil moisture content,total nitrogen,C/N,Leucine Aminopeptidase,p H and bulk density were the main factors affecting soil organic carbon accumulation and mineralization after vegetation restoration,especially soil total nitrogen,which has a more direct positive relationship with soil organic carbon accumulation.（5）In the karst rocky desertification area of southwest China,the vegetation restoration of honeysuckle,cypress-trees,and teak（vine,arbor forest）plantation is beneficial to soil organic carbon storage,while the vegetation restoration of imperial bamboo gras and amomum（herb）is not conducive to soil organic carbon storage.The results of this study provide an important scientific basis for the scientific restoration of vegetation in karst rocky desertification area in southwest China,and also have important significance for reducing soil carbon emission and increasing carbon sequestration to cope with global climate change.