Effects of different plantations on the activity of soil enzymes and their kinetic characteristics in subtropical zone

The activity of three soil enzymes (ureases, peroxidases and polyphenol oxidases) and the corresponding kinetic characteristics (V_max, V_max/K_m and K_m) were studied by comparing four regenerated plantations (Cunninghamia lanceolata plantation, Liriodendron chinense plantation, Pinus massoniana plantation, Alnus-Liriodendron mixed plantation) with the local natural secondary forests in subtropical zone of Dagang Mountains of Jiangxi Province.The results showed that:1) the enzyme activity, V_max and V_max/K_m of soil ureases, peroxidases and polyphenol oxidases of the four different plantations decreased with the increase of soil depth;2) comparing with the natural secondary forests, the activity of ureases, peroxidases and polyphenol oxidases of C.lanceolata plantation decreased by 35%, 4% and 58% respectively in the depth of 0-0.2 m, while V_max and V_max/K_m of soil ureases decreased by 46% and 47%;3) the activity of other soil enzymes had the same tendency in this plantation;4) and the soil enzyme activity and kinetic characteristics in the L.chinense plantation decreased too.In the soil depth of 0 (-) 0.2 m and 0.2 (-) 0.4 m in P.massoniana plantation, the activity of ureases decreased by 54% and 62% respectively, while the peroxidases both increased by 23%, and polyphenol oxidases decreased by 28% and 42% respectively.K_m of peroxidases decreased by 44% and 48%, while V_max/K_m increased by 58% and 92% respectively.All the kinetic parameters of soil ureases decreased evidently, while polyphenol oxidases increased;5) the activity of soil ureases and polyphenol oxidases in the depth of 0 (-) 0.2 m of the Alnus-Liriodendron mixed forests decreased by 38% and 9%, and V_max/K_m of ureases, peroxidases and polyphenol oxidases decreased by 7%, 38% and 54% respectively, but the activity of peroxidases showed no evident changes.