森林转换对土壤氮相关水解酶活性的影响

Effects of Forest Conversion on Soil Nitrogen Related Hydrolase Activities

森林转换会对土壤生态过程产生显著影响,其中土壤酶是土壤系统不可缺少的重要组成部分,能表征土壤C,N,P等养分的循环状况,因此研究森林转换对土壤酶活性的影响具有重要意义。此外,不同底物浓度下酶活性差异大,底物浓度如何影响不同森林土壤酶活性越来越受到关注。以福建省顺昌县武坊林场常绿阔叶天然林和杉木人工林为研究对象,采用96微孔酶标板荧光分析法,通过设置2种底物浓度研究与氮循环有关的2种水解酶(β-1,4-N-乙酰葡糖氨糖苷酶和亮氨酸氨基肽酶)活性在不同土层(0~10、10~20和20~40 cm)的分布规律及对森林转换的响应。研究表明:(1)在天然林中高浓度(400μM)和低浓度(200μM)下β-1,4-N-乙酰葡糖氨糖苷酶(NAG)与亮氨酸氨基肽酶(LAP)活性随土层加深呈现先减小后增加的趋势,提高底物浓度后,表层和深层土壤NAG酶活性以及深层土壤LAP酶活性增大。(2)在人工林中2种底物浓度下NAG酶活性随着土层的加深而逐渐减少,土层对低浓度(200μM)NAG酶有显著影响(P<0.05),提高底物浓度会增加各土层NAG酶活性;低浓度(200μM)LAP酶活性在表层土壤最低,随土层深度增加呈现先增加后减少的趋势;土层对高浓度LAP酶活性有显著影响(P<0.05)。(3)在表层和深层土壤中,相同底物浓度的同种酶活性表现为天然林>人工林,不同林分对高浓度(400μM)LAP酶有显著影响(P<0.05)。(4)土壤理化性质(pH、粒径、全碳和全氮)与不同浓度下NAG和LAP酶活性无显著相关,200μM浓度下LAP活性与不同浓度NAG酶活性呈显著负相关(P<0.05)。

Forest conversion will have a significant impact on soil ecological process,in which soil enzymes are an indispensable part of soil system,which can characterize the cycling status of soil nutrients such as C,N and P.Therefore,it is of great significance to study the impact of forest conversion on soil enzyme activities.In addition,enzyme activity varies greatly under different substrate concentration,but how substrate concentrations affect enzyme activity in different forest soils is receiving increasing attention.In this study,the natural evergreen broad-leaved forest and Chinese fir plantation in Wufang Forest Farm in Shunchang,Fujian Province were selected as the research objects.The 96 microporous enzyme plate fluorescence analysis was used to investigate the distribution of the activities of two hydrolases(β-1,4-N-acetylglucosaminidase and leucine aminopeptidase)related to the nitrogen cycle in different soil layers(0~10,10~20 and 20~40 cm)and their responses to forest conversion were studied by setting the concentrations of two substrates(200μM and 400μM).The results showed that,(1)the activities ofβ-1,4-n-acetylglucosaminoglycosidase(NAG)and leucine aminopeptidyase(LAP)in natural forests at high concentrations(400μM)and low concentrations(200μM)decreased first and then increased with the increase of soil depth.Increasing the substrate concentration leads to an increase in NAG enzyme activity in surface and deep soil layers,as well as LAP enzyme activity in deep soil layers.(2)In the plantation forest,the NAG enzyme activity decreased gradually with the increase of soil depth,soil depth had a significant effect on NAG enzyme activity at the low concentration(200μM)(P<0.05),the increasing substrate concentration will increase the NAG enzyme activity in each soil layer.At low concentration(200μM),LAP enzyme activity was the lowest in the surface soil,and increased first and then decreased with the increase of soil depth.Soil depth had a significant effect on LAP enzyme activity at high substrate concentration(P<0.05).(3)In both surface and deep soil layers,soil enzyme activities at the same substrate concentration were higher in natural forest than in plantation forests,and different stands had significant effects on LAP enzyme at the high concentration(400μM)(P<0.05).(4)Soil physiochemical properties(pH,particle size,total carbon and total nitrogen)had no significant correlation with NAG and LAP enzyme activities at different concentration.LAP activity at 200μM concentration was significantly negatively correlated with NAG enzyme activity at different concentrations(P<0.05).