氮沉降对滇中亚高山云南松林土壤酶活性及其化学性质的影响

Impact of nitrogen deposition on soil enzyme activities and chemical properties in Pinus yunnanensis forest in the central subalpine region of Yunnan

【目的】探究氮沉降下土壤酶活性、化学性质的变化,了解滇中高原森林土壤养分的循环状况。【方法】以滇中亚热带云南松(Pinus yunnanensis)林为研究对象,设置对照(CK,氮沉降为0),以及低氮(LN,10 g·m^(-2)·a^(-1)氮沉降)、中氮(MN,20 g·m^(-2)·a^(-1)氮沉降)和高氮(HN,25 g·m^(-2)·a^(-1)氮沉降)3个处理,进行氮沉降模拟试验。【结果】LN、MN、HN处理的蔗糖酶(invertase,Inv)活性提高了7.45%~14.04%,脲酶(urease,Ure)活性下降11.16%~27.17%,酸性磷酸酶(acid phosphatase,ACP)活性下降5.18%~16.67%,过氧化氢酶(catalase,CAT)活性下降7.22%~23.35%;土壤酶活性均呈显著的时间梯度变化(P<0.05),Inv和Ure分别在氮沉降时间为31、29月时达到最低值和最高值;ACP和CAT活性均在氮沉降时间为33月时达到最高值。随着氮沉降水平的提高土壤pH值,有机碳、全磷含量分别下降1.59%~4.79%、21.25%~45.96%和17.68%~46.15%;土壤全氮和硝态氮含量分别在MN、HN处理达到最高值。不同土层土壤酶活性和土壤化学性质的分布特征均表现为0~5 cm土层>5~10 cm土层>10~20 cm土层;氮沉降下不同土壤酶活性之间的相关性较高(P<0.05);土壤pH、氨态氮与Inv活性呈显著正相关(P<0.05);土壤有机碳和全磷含量与Ure、ACP和CAT活性呈显著正相关(P<0.05)。【结论】氮沉降增强了土壤酶活性之间的相关性,改变了土壤的环境因子,进而改善了土壤中养分元素的循环状况。

【Objective】The impact of nitrogen deposition on soil enzyme activity and chemical properties was investigated aiming to understand the nutrient cycling in forest soil in the central subalpine region of Yunnan Province in the context of increased N deposition.【Method】Field simulation experiment of nitrogen deposition was conducted in Pinus yunnanensis forests in the central subtropical region of Yunnan,with 4 N gradient treatments of[control(CK,0 g·m^(-2)·a^(-1)nitrogen deposition),low N(LN,10 g·m^(-2)·a^(-1)nitrogen deposition),medium N(MN,20 g·m^(-2)·a^(-1)nitrogen deposition)and high N(HN,25 g·m^(-2)·a^(-1)nitrogen deposition)].【Result】Nitrogen deposition generally promoted the invertase activity by 7.45%-14.04%,while inhibited the activities of urease(↓11.16%-27.17%),acid phosphatase(↓5.18%-16.67%)and catalase(↓7.22%-23.35%).Soil enzyme activities showed various significant temporal gradients(P<0.05):the activities of sucrase and urease exhibited unimodal patterns,with the lowest and highest points at 31 and 29 months under nitrogen deposition,respectively;the activities of acid phosphatase and catalase,however,did not showed clear variation pattern,both peaking at 33 months under nitrogen deposition.Soil pH,organic carbon and total phosphorus content were down by 1.59%-4.79%,21.25%-45.96%,and 17.68%-46.15%,respectively,with increased nitrogen deposition,while soil total N and nitrate N reached the maximums at MN and HN,respectively.Moreover,soil enzyme activities and chemical properties all decreased progressively in response to vertical soil layer,with a pattern of 0-5 cm>5-10 cm>10-20 cm.Under nitrogen deposition,there was significant synergistic effect(P<0.05)among different soil enzymes,with soil pH and ammonium N being the main positive factors affecting invertase activity,and soil organic carbon and total phosphorus being the main positive factors affecting the activities of urease,acid phosphatase and catalase(P<0.05).【Conclusion】Nitrogen deposition enhances the collaborative mechanisms between soil enzymes,alters the environmental factors,affects the soil enzyme activities,and consequently changes the nutrient cycling of forest soils.