[Soil enzyme activities and their stoichiometry of typical plantations in mid-subtropical China]

We measured the activities of six kinds of enzyme, including β-glucosidase (BG), β-N-acetyl-glucosaminidase (NAG), leucine aminopeptidase (LAP), acid phosphatase (AP), polyphenol oxidase (POX), peroxidase (POD), as well as enzyme stoichiometric ratios and soil physical and chemical properties at 0-10 and 10-20 cm layers across typical Pinus massoniana plantation, Pinus elliottii plantation and mixed plantation of P. massoniana and Schima superba (broadleaved-conifer mixed plantation) in mid-subtropical China. Key factors driving the variation in soil enzyme activity and stoichiometry among different stand types were investigated. The results showed that the activities of soil BG and LAP were significantly affected by stand type. Soil BG activity at 10-20 cm soil layer was significantly higher in P. elliottii plantation than in P. massoniana plantation, while the activity of LAP was highest in the P. massoniana plantation. Soil BG/(NAG+LAP) and BG/AP at 10-20 cm layer of P. elliottii plantation were significantly higher than those of P. massoniana plantation, while (NAG+LAP)/AP of P. massoniana plantation was significantly higher than those of P. elliottii plantation and mixed plantation. The vector length of enzyme stoichiometry at 10-20 cm soil layer was significantly different among stand type, with an order of P. elliottii plantation > broadleaved-conifer mixed plantation > P. massoniana. The vector angles of enzyme stoichiometry in the three plantations were greater than 45°, with the vector angle in the P. elliottii plantation at 10-20 cm soil layer being significantly greater than that of the P. massoniana plantation. Results from redundancy analysis showed that soil carbon quality index and the ratio of soil organic carbon to total phosphorus (C/P), soil water content and C/P were the key factors affecting soil enzyme activity and stoichiometry at 0-10 and 10-20 cm soil layers, respectively. The quantity and quality of soil carbon and phosphorus, and soil water content played a key role in regulating nutrient cycling in mid-subtropical plantation ecosystem.