Response of soil microbial communities to natural and managed vegetation restoration in a subtropical karst region

Abstract

The soil microbial community is a key indicator to evaluate the effectiveness of vegetation restoration in degraded ecosystems. However, few studies have simultaneously compared the effects of managed and natural vegetation restoration strategies on the soil microbial community in the ecologically fragile karst region using signature lipid biomarker analysis to provide information on a variety of microbial properties. Here, phospholipid fatty acids (PLFAs) in the soil microbial community were measured following different restoration strategies in a karst region of southwest China. Managed vegetation restoration (including restoration with plantation forest, forage grass, and a combination of plantation forest and forage grass) and natural vegetation restoration (spontaneous regeneration to natural grassland) were compared, using cropland as a reference. The abundance of total PLFAs and the PLFAs of four microbial functional groups (bacteria, fungi, actinomycetes, and arbuscular mycorrhizal fungi [AMF]) significantly increased in the topsoil (0–5 cm soil depth) following vegetation restoration. In the sub-topsoil layer (5–10 cm soil depth), the abundance of PLFAs was not significantly higher than that in the cropland, except in AMF in natural vegetation restoration. Principal component analysis indicated that the microbial PLFA composition differed between the restoration strategies, and the abundance of AMF PLFAs was significantly higher in natural than in managed vegetation restoration for both soil depths. The ratio of soil organic carbon to total nitrogen and dissolved organic carbon content were the primary factors affecting the abundance of soil microbial communities in the topsoil and sub-topsoil, respectively. In addition, soil pH served as another explanatory variable for the topsoil. Our findings suggest that vegetation restoration over a relatively short period (15 years) mainly improved topsoil fertility. Moreover, natural vegetation restoration may be superior to managed vegetation restoration for the maintenance of multiple ecosystem functions in the short term in the karst regions, owing to the potentially significant role of AMF.