Dynamics of Enzyme Activities during the Decomposition of Castanopsis carlesii Leaf Litter in the Forest Canopy and Forest Floor in a Mid-Subtropical Area

Abstract

Enzyme activity plays a pivotal role in leaf litter decomposition, but the variations have not been well addressed in the forest canopy with amounts of leaf litter. Therefore, eight enzymes related to carbon, nitrogen, and phosphorus mineralization were checked during Castanopsis carlesii leaf litter decomposition in the forest canopy and on the forest floor from April 2021 to February 2022. The results displayed that most enzyme activities were lower in the forest canopy compared to the forest floor during litter decomposition, except for acid phosphatase, polyphenol oxidase, and peroxidase activities. Moreover, enzyme stoichiometry and enzyme vector features indicated that the microbes in both habitats were limited by carbon and phosphorus during litter decomposition. Much stronger carbon limitation was detected on the forest floor, while phosphorus limitation was higher in the forest canopy. Phosphorus limitation was weakened, but carbon limitation was strengthened in the forest canopy with leaf litter decomposition. Additionally, the redundancy analysis revealed that air temperature dominated the variations in enzyme activities during litter decomposition in the forest canopy, and litter mass-loss rate in each period explained much more dynamics on the forest floor compared with those in the forest canopy. These results provide new insight into a comprehensive understanding of litter decomposition in subtropical forests.