Determinants of soil extracellular enzyme activity in a karst region, southwest China

Abstract

Soil extracellular enzymes are crucial in biogeochemical cycling and ecosystem functioning. Most previous studies addressed the determinants of soil extracellular enzyme activity (EEA) in small-scale regions with acid soils, yet uncertainty exists in large-scale regions with alkaline soils. In this study, the activities of 7 soil extracellular enzymes related to carbon, nitrogen and phosphorus cycling were assayed in a regional-scale karst area, southwest China. Soil samples were collected from secondary forest, shrubland, grassland and cropland underlain by either dolomite or limestone. The enzyme activity profiles were significantly different between dolomite and limestone or among the four land use types according to multi-response permutation procedure analysis. Variation partitioning indicated that soil properties, spatial variables and land use together explained 43% of EEA variation. Soil properties explained the largest proportion of EEA variation (36.5%). The variation explained by spatial variables and land use was mostly shared with soil properties, resulting in small unique fractions explained by these two factors (5.5%), especially spatial variables (2.2%). Among the soil properties, soil moisture, contents of silt and total nitrogen were the most important variables responsible for EEA variation. Our results suggest that regional EEA variation can be well explained by soil properties in the karst regions.