Responses of soil labile organic carbon fractions and enzyme activities to long-term vegetation restorations in the karst ecosystems, Southwest China

Abstract

To reveal the effects of karst long-term vegetation restorations on total soil organic carbon (TSOC), labile organic carbon fractions and enzymes, in the present study, the typical karst vegetation restoration region of Southwest China was selected as study area. Four types of long-term vegetation restoration engineering including seven kinds of planting measures were selected as study objects. Responses of TSOC and its labile fractions accumulation and distribution to the different vegetation restorations were studied. And the effects of these vegetation restorations on soil enzymes activities of urease, sucrase, amylase, and alkaline phosphatase were also researched. Results showed the vegetation restorations significantly improved TSOC accumulation and obviously changed microbial biomass carbon (MBC), easy oxidated organic carbon (EOC), and dissolved organic carbon (DOC) contents and their proportions to TSOC. And the effects of these different vegetation restorations on TSOC and its labile fractions were obviously different. TSOC content and reserves, MBC and EOC contents of Cupressus funebris and Lonicera japonica planting were high. While TSOC content and reserves of the two grassland restoration measures were the lowest. The vegetation restorations significantly increased soil enzyme activities of amylase (AMY), alkaline phosphatase (ALP), urease (URE) and sucrose (SUC). And there were significant differences in responses of different soil enzyme activities to vegetation restorations. The four soil enzyme activities were significantly correlated with TSOC and its labile fractions contents, especially soil AMY and ALP. Soil ALP and AMY were closely related to TSOC mineralization and accumulation and the formation and transformation of labile organic carbon fractions in Southwest China karst ecosystems. The present results provided scientific bases for the vegetation restoration of degraded karst ecosystems and were of great significance in carbon cycle intervention based on land use regulation in Southwest China.