Soil enzyme activities and microbial nutrient limitation during the secondary succession of boreal forests

Extracellular enzymes are the proximate agents of organic matter decomposition, and its activity can be used as an indicator of microbial nutrient demand. The secondary succession of ecosystem will change the soil properties and microbial community structure, which will affect the nutrient cycle and stability of the ecosystem. However, the research on the changes of soil enzymes during the succession in the boreal forest ecosystems is still lack of insight. Using the method of 'space-for-time substitution', we selected four habitats (including grassland, Betula platyphylla forest, Larix gmelinii and Betula platyphylla mixed forest and Larix gmelinii forest) in Greater Khingan Mountains northeastern China to represent the secondary successional sequence of boreal forests, and studied the response mechanism of soil enzyme activities and microbial nutrient limitation to secondary succession of ecosystem after burning. The results showed that during the succession, phosphorus (P) limitation gradually weakened, nitrogen (N) limitation gradually strengthened, and the ratio of carbon (C): N: P of soil enzymes gradually tended to 1: 1: 1. With the progress of succession, C (BG, & beta;-1,4-glucosidase; CBH, & beta;-D-cellobiosidase), N (NAG, & beta;-1,4-N-acetylglucosaminidase; LAP, L-leucine aminopeptidase) related enzyme activity increased and P (AP, acid phosphatase) related enzyme activity did not change significantly. During the secondary succession of ecosystem after burning, the soil microbial community maintains homeostasis, and the nutrient limitation of microorganisms largely depends on the content and stoichiometry of soil nutrients.