摘要
在山西太岳山森林生态系统国家定位观测研究站的研究区域,选取立地条件基本一致的天然油松(Pinus tabuliformis)林为研究样地,于2015年5月份建立试验样地20块(每块样地15 m×15 m);采用随机区组设计,试验样地内设置1个对照处理和4个梯度添加氮处理(0、5、10、20、40 g·m^(-2)·a^(-1)),每个梯度设置4个重复,添加的氮源为硝酸铵,在每年的6月份对各样地进行施氮处理;2019年8月份,在每块样地内随机选取3个取样点,用内径5 cm的土钻采集0~10 cm土层的土壤样品,测定土壤微生物生物量碳、微生物生物量氮、微生物生物量磷、土壤酶活性、土壤理化性质;采用单因素方差分析法、最小显著差异法(LSD)分析不同氮处理间土壤基本理化性质的差异,采用回归分析法分析土壤微生物氮利用效率与各形态氮素的相关性,采用结构方程模型通径分析微生物氮利用效率的驱动因素间相关性。结果表明:①添加氮时土壤全氮质量分数、有机氮质量分数无显著变化;无机氮质量分数,从不施氮时的4.89 mg·kg^(-1)显著提高到施氮量为40 g·m^(-2)·a^(-1)时的177.63 mg·kg^(-1),增加了35.3倍;微生物生物量氮的质量分数、与氮获取酶相关酶的活性(β-N-乙酰氨基葡萄糖苷酶活性+亮氨酸氨肽酶活性),随施氮量的增加出现先升高后降低的趋势,均在施氮量为40 g·m^(-2)·a^(-1)时最小,显著低于不施氮时12.5%、27.9%。②添加氮对微生物氮利用效率有显著的促进作用,由对照(施氮量0)时的0.18增大到施氮量40 g·m^(-2)·a^(-1)时的0.60,提高了2.3倍(P<0.05)。③微生物氮利用效率,受土壤pH、碳氮比(碳质量分数w(C)∶氮质量分数w(N))、微生物生物量碳氮比(生物量碳质量分数w(C_(MB))∶生物量氮质量分数w(N_(MB)))、氮获取酶相对活性[(β-N-乙酰氨基葡萄糖苷酶活性+亮氨酸氨肽酶活性)/(β-1,4-葡萄糖苷酶活性+β-N-乙酰氨基葡萄糖苷酶活性+亮氨酸氨肽酶活性+酸性磷酸酶活性)]的显著影响;微生物氮利用效率,与pH、w(C)∶w(N)、氮获取酶相对活性呈正相关,与w(C_(MB))∶w(N_(MB))呈负相关。④综合试验结果,说明添加氮通过影响土壤氮及其各组分的构成,使土壤微生物由养分(氮)限制转化为能量(碳)限制,提高了微生物对氮的利用效率。
In the research area of the National Positioning Observation and Research Station of forest ecosystem in Taiyue Mountain,Shanxi Province,the natural Pinus tabuliformis forest with basically the same site conditions was selected as the research sample,and 20 experimental plots(each plot 15 m×15 m)were established in May 2015.A randomized block design was adopted,and 1 control treatment and 4 gradient nitrogen(N)addition treatments(0,5,10,20 and 40 g·m^(-2)·a^(-1))were set up in the experimental plot,with 4 replicates per gradient,the added N source is ammonium nitrate,which is applied to various fields in June each year.In August 2019,three sampling points were randomly selected in each sample plot,and soil samples of 0-10 cm soil layer were collected with a soil drill with an inner diameter of 5 cm,and soil microbial biomass C,microbial biomass N,microbial biomass P,soil enzyme activity,and soil physical and chemical properties were determined.The difference of soil basic physical and chemical properties between different N treatments was analyzed by single factor analysis of variance and least significant difference(LSD).The correlation between soil microbial N use efficiency and various N forms was analyzed by regression analysis.The correlation between driving factors of microbial N use efficiency was analyzed by structural equation model.The results showed as follows:(1)There were no significant changes in soil total N content and organic N content when N was added.The content of inorganic N was significantly increased from 4.89 mg·kg^(-1) when no N was applied to 177.63 mg·kg^(-1) when N was applied to 40 g·m^(-2)·a^(-1) by 35.3 times.The content of microbial biomass N and the activities of enzymes related to N acquisition enzyme(β-N-acetylglucosaminidase activity+leucine aminopeptidase activity)firstly increased and then decreased with the increase of N application rate,and the minimum values were found at 40 g·m^(-2)·a^(-1),which were significantly lower than 12.5%and 27.9%at no N application rate.(2)N addition had a significant effect on microbial N use efficiency,which was increased by 2.3 times from 0.18 in the control group(N rate 0)to 0.60 in the control group(N rate 40 g·m^(-2)·a^(-1))(P<0.05).(3)Microbial N use efficiency,It was affected by soil pH,C/N ratio(w(C)∶w(N)),microbial biomass C/N ratio(w(C_(MB))∶w(N_(MB))),and the relative activity of N harvesting enzyme[(β-N-acetylglucosaminase activity+leucine aminopeptidase activity)/(β-1,4-glucosidase activity)Activity+β-N-acetylglucosaminidase activity+leucine aminopeptidase activity+acid phosphatase activity]had significant effects.Microbial N use efficiency was positively correlated with pH,w(C)∶w(N)and the relative activity of N harvesting enzyme,but negatively correlated with w(C_(MB))∶w(N_(MB)).(4)Comprehensive test results show that the addition of N can change soil microorganisms from nutrient(N)restriction to energy(C)restriction by affecting the composition of soil N and its components,and improve the efficiency of microbial N utilization.
作者
杨金婕
王勇强
周志勇
沈颖
Yang Jinjie;Wang Yongqiang;Zhou Zhiyong;Shen Ying(Beijing Forestry University,Beijing 100083,P.R.China;Shanxi Lingkong Mountain National Nature Reserve Administration)
出处
《东北林业大学学报》
CAS
CSCD
北大核心
2023年第8期40-47,共8页
Journal of Northeast Forestry University
基金
科技部科技基础资源调查专项项目(2022FY1001013)
林草科技创新发展研究项目(2022132265)。
关键词
添加氮
油松林
土壤微生物氮
氮循环
Nitrogen addition
Pinus tabulaeformis forest
Soil microbial nitrogen
Nitrogen cycle
