Abstract:
Objective To study the effects of simulated N deposition on soil enzyme activity in different forest types.
Method Pinus yunnanensis forest, Quercus semecarpifolia forest, Pinus armandii forest and evergreen broadleaved forest were used as the research objects in the typical forests at Mopan mountain, central Yunnan. From January to December, 2018, four N treatments including CK (0 g N m−2·a−1), low N (LN, 5 g N m−2·a−1), medium N (MN, 15 g N m−2·a−1) and high N (HN, 30 g N m−2·a−1) were set to determine the activities of invertase, amylase, urease, asparaginase, acid phosphatase, protease, catalase and polyphenol oxidase in different soil layers (0~5 cm, 5~10 cm and 10~20 cm) of the four forest areas at different N levels.
Result The results showed that the effect of soil depth on the activity of the eight soil enzyme in these forests was lower in 10~20 cm soil than in 5~10 cm soil, with a maximum decrease of 76.8%. The activities of catalase in evergreen broadleaved forest and P. yunnanensis forest and polyphenol oxidase in Q. semecarpifolia forest and P. yunnanensis forest were inhibited in 0~5 cm soil layer, and the lowest activity was only 15.4% of that in the soil layer of 5~10 cm. The N level had a significant effect on soil enzyme activity. LN significantly inhibited the activity of invertase and amylase in Q. semecarpifolia forest. N treatment had no significant effect on urease and protease activity. LN treatment significantly increased the activity of asparaginase and acid phosphatase in soil layer 0~10 cm except evergreen broadleaved forest. The N treatment inhibited the soil catalase activity in P. armandii forest and the soil polyphenol oxidase activity in each forest, and promoted the soil catalase activity in Q. semecarpifolia forest and P. yunnanensis forest. Forest type had significant effects on soil invertase, amylase, urease, asparaginase, acid phosphatase, protease, catalase and polyphenol oxidase (P < 0.01).
Conclusion Forest type and soil depth are important factors affecting the differentiation of soil invertase, amylase, urease, asparaginase, acid phosphatase, protease and catalase activity under N sedimentation. Soil polyphenol oxidase activity is sensitive to N sedimentation but not to forest type. Among the eight soil enzymes, asparaginase is the most sensitive to the interaction among soil depths, N application level and forest type.