{"title":"[Short-term nitrogen addition reduces soil microbial nitrogen fixation rate in subtropical <i>Pinus taiwanensis</i> and <i>Castanopsis faberi</i> forests].","authors":"Lin-Na Chen, Quan-Xin Zeng, Xiao-Qing Zhang, Qiu-Fang Zhang, Xiao-Chun Yuan, Hui Dai, Wen-Zhou Li, Yue-Min Chen","doi":"10.13287/j.1001-9332.202404.016","DOIUrl":null,"url":null,"abstract":"<p><p>Biological nitrogen (N) fixation is an important source of N in terrestrial ecosystems, but the response of soil microbial N fixation rate to N deposition in different forest ecosystems still remains uncertain. We conducted a field N addition experiment to simulate atmosphere N deposition in subtropical <i>Pinus taiwanensis</i> and <i>Castanopsis faberi</i> forests. We set up three levels of nitrogen addition using urea as the N source: 0 (control), 40 (low N), and 80 g N·hm<sup>-2</sup>·a<sup>-1</sup>(high N) to examine the chemical properties, microbial biomass C, enzyme activities, and <i>nifH</i> gene copies of top soils (0-10 cm). We also measured the microbial N fixation rate using the <sup>15</sup>N labeling method. Results showed that N addition significantly reduced the soil microbial N fixation rate in the <i>P. taiwanensis</i> and <i>C. faberi</i> forests by 29%-33% and 10%-18%, respectively. Nitrogen addition significantly reduced N-acquiring enzyme (i.e., β-1, 4-N-acetylglucosaminidase) activity and <i>nifH</i> gene copies in both forest soils. There was a significant positive correlation between the microbial N fixation rate and soil dissolved organic C content in the <i>P. taiwanensis</i> forest, but a significant negative relationship between the rate of soil microbial nitrogen fixation and NH<sub>4</sub><sup>+</sup>-N content in the <i>C. faberi</i> forest. Overall, soil microbial N fixation function in the <i>P. taiwanensis</i> forest was more sensitive to N addition than that in the <i>C. faberi</i> forest, and the factors affecting microbial N fixation varied between the two forest soils. The study could provide insights into the effects of N addition on biological N fixation in forest ecosystems, and a theoretical basis for forest management.</p>","PeriodicalId":35942,"journal":{"name":"应用生态学报","volume":null,"pages":null},"PeriodicalIF":0.0000,"publicationDate":"2024-04-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"应用生态学报","FirstCategoryId":"1087","ListUrlMain":"https://doi.org/10.13287/j.1001-9332.202404.016","RegionNum":0,"RegionCategory":null,"ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q3","JCRName":"Environmental Science","Score":null,"Total":0}
引用次数: 0
Abstract
Biological nitrogen (N) fixation is an important source of N in terrestrial ecosystems, but the response of soil microbial N fixation rate to N deposition in different forest ecosystems still remains uncertain. We conducted a field N addition experiment to simulate atmosphere N deposition in subtropical Pinus taiwanensis and Castanopsis faberi forests. We set up three levels of nitrogen addition using urea as the N source: 0 (control), 40 (low N), and 80 g N·hm-2·a-1(high N) to examine the chemical properties, microbial biomass C, enzyme activities, and nifH gene copies of top soils (0-10 cm). We also measured the microbial N fixation rate using the 15N labeling method. Results showed that N addition significantly reduced the soil microbial N fixation rate in the P. taiwanensis and C. faberi forests by 29%-33% and 10%-18%, respectively. Nitrogen addition significantly reduced N-acquiring enzyme (i.e., β-1, 4-N-acetylglucosaminidase) activity and nifH gene copies in both forest soils. There was a significant positive correlation between the microbial N fixation rate and soil dissolved organic C content in the P. taiwanensis forest, but a significant negative relationship between the rate of soil microbial nitrogen fixation and NH4+-N content in the C. faberi forest. Overall, soil microbial N fixation function in the P. taiwanensis forest was more sensitive to N addition than that in the C. faberi forest, and the factors affecting microbial N fixation varied between the two forest soils. The study could provide insights into the effects of N addition on biological N fixation in forest ecosystems, and a theoretical basis for forest management.