Soil Enzyme Activity and Stoichiometry in an Illicium verum Plantation Chronosequence in Southern China

Soil extracellular enzyme stoichiometry reflects the growth and metabolic processes of microorganisms and the potential for soil nutrient limitations. However, knowledge of shifts in soil extracellular enzyme stoichiometry and nutrient limitation within forest plantation chronosequences remains limited. This study sampled soils from Illicium verum plantations of different ages in a tropical mountain area in southern China. Here, we determined the activities of four extracellular enzymes (beta-1,4-glucosidase, beta-1,4-N-acetylglucosaminidase, leucine aminopeptidase, and acid phosphate), C:N:P acquisition ratios, and soil physicochemical properties. Results showed with increasing stand age, the soil total N (STN), soil available N (SAN), soil organic carbon (SOC), and soil C:N:P ratios increased significantly, while the soil total P (STP) and soil available P (SAP) showed no significant changes. Furthermore, as stands age increased the activities of the four enzymes increased, the enzymatic N:P and C:P ratios decreased significantly, and the enzyme C:N ratio showed no significant changes. Additionally, the activities of the four enzymes and their stoichiometry were significantly positively correlated with the soil water content, SOC, STN and SAN but negatively correlated with the STP and SAP. The enzymatic C:N:P ratio was 1:1:1.4, indicating that the soil P availability limited the growth of microorganisms in I. verum plantations. Results provide important insights into the sustainable management of I. verum plantations in southern China.