Abstract: Aims The purpose of this study is to reveal the impacts of long-term vegetation restorations on soil total organic carbon, active organic carbon fractions and enzyme activities in karst rocky desertification ecosystems and provide scientific bases for the scientific control of degraded karst ecosystems and carbon regulation based on land use in Southwest China. Methods In the typical karst area of Southwest China, seven representative vegetation restoration measures, that is, Cupressus funebris planting, Tectona grandis planting, Zanthoxylum bungeanum planting, Hylocereus undatus planting, Lonicera japonica planting, Pennisetum sinese planting and Amomum villosum planting, were selected. Responses of contents of soil total organic carbon (TSOC), microbial biomass carbon (MBC), dissolved organic carbon (DOC) and easy oxidation organic carbon (EOC) and enzyme activities of urease (URE), sucrase (SUC), amylase (AMY) and alkaline phosphatase (ALP) to these vegetation restorations were studied. Important findings (1) The vegetation restorations significantly improved TSOC distribution and accumulation and remarkably changed soil active organic carbon fraction contents and their proportions to TSOC in the karst rocky desertification ecosystem. And the impacts of different vegetation restorations on contents of TSOC and its active fractions were obviously different. TSOC contents and reserves of C. funebris and L. japonica planting were high, while those of the two measures of artificial grassland construction (P. sinese and A. villosum planting) were the lowest among the seven vegetation restorations studied. EOC and MBC contents of C. funebris and L. japonica planting were high, while DOC contents of Z. bungeanum planting were high. (2) The four soil enzymes activities were all significantly raised in vary degrees by the long-term vegetation restorations. However, response laws of different soil enzyme activities to the vegetation restorations were obviously different. Excluding Z. bungeanum planting, URE activities of the other six restoration measures were significantly higher than that of CK. Except of P. sinese planting, SUC and ALP activities of the remaining six restoration measures were significantly higher than those of CK. Among the seven restoration measures, only AMY activity of C. funebris planting was significantly higher than that of CK. (3) There were significant correlations between soil enzyme activities and contents of TSOC and its active fractions. And correlations of different enzyme activities with TSOC and its active fraction contents were obviously different. Correlations of AMY and ALP activities with TSOC and its active fraction contents were higher than that of URE and SUC. ALP and AMY activities were closely related to soil organic carbon accumulation and mineralization and active organic carbon fraction formation and transformation in the karst rocky desertification ecosystem.

Key words: Vegetation restoration, Enzyme activity, Microbial biomass carbon, Dissolved organic carbon, Easy oxidation organic carbon