不同水氮水平对川西亚高山林地土壤酶活性的影响

Dynamic effects of nitrogen deposition on soil enzyme activities in soils with different moisture content

为探讨氮沉降在不同土壤水分状况下对林下土壤中参与土壤碳氮磷循环主要酶(β D 葡萄糖苷酶(β D glucosidase,βG)、过氧化物酶(Peroxidase,PER)、多酚氧化酶(Polyphenol oxidase,PPO)、β N 乙酰葡糖胺糖苷酶(β N acetylglucosaminidase,NAG)和酸性磷酸酶(Acid phosphatase,AP))活性的动态影响,于2017年开展了盆栽模拟试验。试验以青杨扦插苗为植物材料,采用两因素(土壤水分和氮沉降)的随机区组设计,土壤水分含量分别为40%(W40)、60%(W60)和80%(W80)最大田间持水量,氮沉降水平分别为:0(N0)、4(N4)和8(N8)g N m^-2 a^-1。在土壤水分达到预定的水分含量后开始氮沉降处理,于氮沉降后的6 h、24 h和3、7、14、31、62 d采集土壤样品进行土壤酶活性的测定。结果表明:土壤含水量的降低显著降低了βG、NAG和PPO活性,且在W40时达到最低;对AP和PER活性无显著影响。氮沉降抑制了βG、NAG和AP活性,而且施氮浓度越大,抑制效应越强;对PER和PPO活性无显著影响。水氮交互作用对上述5种土壤酶活性均无显著影响。5种土壤酶活性在施氮7 d或14 d内变化较大,之后随处理时间的延长逐步平稳。两个月的实验期间,在不同水氮处理下,5种土壤酶活性基本都呈现升高 降低 升高 降低的双峰模式。该研究可为理解氮沉降对不同水分状况地区森林生态系统中土壤碳氮磷循环的生态学过程提供科学参考。

To investigate the effects of nitrogen deposition on activities of soil enzymes(β D glucosidase(βG),Peroxidase(PER),Polyphenol oxidase(PPO),β N acetylglucosaminidase(NAG),Acid phosphatase(AP))involved in carbon,nitrogen,and phosphorus cycles in soils with different moisture content,we conducted a pot simulation experiment in 2017.In the experiment,cuttings of Populus cathayana Rehd were used as plant materials and a randomized block design of two factors(soil moisture and nitrogen deposition)was applied.The soil moistures were 40%(W40),60%(W60),and 80%(W80)of field capacity,respectively;and nitrogen deposition levels were 0(N0),4(N4),and 8(N8)g N m^-2 a^-1,respectively.When the soil moisture reached the predetermined moisture content,the simulated nitrogen deposition treatment was started.The soil samples were collected at 6 h,24 h and 3,7,14,31,and 62 d after nitrogen deposition for the determination of soil enzyme activity.The results showed that the reduction of soil water content decreased significantly the activities ofβG,NAG,and PPO,which have the lowest values at W40.Soil moisture had no significant effect on the activities of AP and PER.Nitrogen deposition inhibited the activities ofβG,NAG,and AP,and the inhibitory effect was greater with increasing nitrogen concentrations,while it has no significant effect on the activities of PER and PPO.No interaction effect between water moisture and nitrogen were observed on the activities of five soil enzymes.The activities of these five soil enzymes varied greatly at 7 d or 14 d,and then gradually stabilized with the extension of treatment time.During the two month experimental period,the activities of five soil enzymes in different water and nitrogen treatments showed a“rise fall rise fall”bimodal pattern.This study can provide better understanding for nitrogen deposition effects on the ecological processes of carbon,nitrogen,and phosphorus cycles in forest ecosystem soils under different water conditions,and also supply guidance for forest management.