滇中亚高山不同森林土壤酶活性对模拟N沉降的响应

Effects of Simulated Nitrogen Deposition on Soil Enzyme Activity in Subalpine Forests in Central Yunnan, China

[目的]研究不同森林类型中模拟N沉降对土壤酶活性的影响,旨在为N素对区域森林土壤酶活性及土壤活动相关研究提供理论依据。[方法]以滇中磨盘山典型森林云南松(Pinus yunnanensis Franch.)林、高山栎(Quercus semecarpifolia Smith)林、华山松(Pinus armandii Franch.)林和常绿阔叶(Evergreen broad-leaf)林为研究对象,于2018年1月—2018年12月设置:对照(CK,0 g N·m^(-2)·a^(-1))、低N(LN,5 g N·m^(-2)·a^(-1))、中N(MN,15 g N·m^(-2)·a^(-1))和高N(HN,30 g N·m^(-2)·a^(-1))4种N处理,测定不同施N水平4种林地0~5、5~10和10~20 cm土层蔗糖酶、淀粉酶、脲酶、天门冬酰胺酶、酸性磷酸酶、蛋白酶、过氧化氢酶、多酚氧化酶活性。[结果]表明:土壤深度对4种森林类型中8种土壤酶活性的影响均表现为10~20 cm土层土壤酶活性低于5~10 cm土层,降幅最高达76.8%,常绿阔叶林与云南松林土壤过氧化氢酶和高山栎林与云南松林土壤多酚氧化酶活性则在0~5 cm土层受到抑制,活性最低时仅为5~10 cm土层活性的15.4%;施N水平对土壤酶活性影响较为显著,LN显著抑制了高山栎林土壤蔗糖酶与淀粉酶活性;各N处理对脲酶、蛋白酶无显著影响;除常绿阔叶林外,LN处理显著提高了0~10 cm土层天门冬酰胺酶和酸性磷酸酶活性,各N处理抑制了华山松林土壤过氧化氢酶活性和各林分土壤多酚氧化酶活性,促进了高山栎林、云南松林土壤过氧化氢酶活性;森林类型对土壤蔗糖酶、淀粉酶、脲酶、天门冬酰胺酶、酸性磷酸酶、蛋白酶、过氧化氢酶和多酚氧化酶影响显著(P<0.01)。[结论]森林类型和土壤深度是影响N沉降下土壤蔗糖酶、淀粉酶、脲酶、天门冬酰胺酶、酸性磷酸酶、蛋白酶和过氧化氢酶活性变化差异的重要因素;土壤多酚氧化酶对施N水平反应敏感,对森林类型反应较不敏感;8种土壤酶中,天门冬酰胺酶对不同土壤深度、不同施N水平和不同森林类型三者交互作用的响应最为敏感。

[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.