title: Combined effects of nitrogen addition and organic matter manipulation on soil respiration in a Chinese pine forest.
abstract: The response of soil respiration (Rs) to nitrogen (N) addition is one of the uncertainties in modelling ecosystem carbon (C). We reported on a long-term nitrogen (N) addition experiment using urea (CO(NH2)2) fertilizer in which Rs was continuously measured after N addition during the growing season in a Chinese pine forest. Four levels of N addition, i.e. no added N (N0: 0 g N m-2year-1), low-N (N1: 5 g N m-2year-1), medium-N (N2: 10 g N m-2year-1), and high-N (N3: 15 g N m-2year-1), and three organic matter treatments, i.e. both aboveground litter and belowground root removal (LRE), only aboveground litter removal (LE), and intact soil (CK), were examined. The Rs was measured continuously for 3 days following each N addition application and was measured approximately 3-5 times during the rest of each month from July to October 2012. N addition inhibited microbial heterotrophic respiration by suppressing soil microbial biomass, but stimulated root respiration and CO2release from litter decomposition by increasing either root biomass or microbial biomass. When litter and/or root were removed, the "priming" effect of N addition on the Rs disappeared more quickly than intact soil. This is likely to provide a point of view for why Rs varies so much in response to exogenous N and also has implications for future determination of sampling interval of Rs measurement.
authors: Key Laboratory for Forest Resources and Ecosystem Processes, Beijing Forestry University, Beijing, 100083, China.|Synthesis Research Center of Chinese Ecosystem Research Network, Key Laboratory of Ecosystem Network Observation and Modeling, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, 100101, China.
authors: Jinsong
authors: J
authors: Wang
authors: Sustainable Soils and Grassland Systems, Rothamsted Research, North Wyke, Okehampton, Devon, EX20 2SB, UK.
authors: L
authors: L
authors: Wu
authors: Key Laboratory for Forest Resources and Ecosystem Processes, Beijing Forestry University, Beijing, 100083, China.
authors: Chunyu
authors: C
authors: Zhang
authors: Key Laboratory for Forest Resources and Ecosystem Processes, Beijing Forestry University, Beijing, 100083, China. zhaoxh@bjfu.edu.cn.
authors: Xiuhai
authors: X
authors: Zhao
authors: College of Forestry, Jiangxi Agricultural University, Nanchang, 330045, China.
authors: Wensheng
authors: W
authors: Bu
authors: Department of Forestry and Wood Technology, University of Stellenbosch, Stellenbosch, South Africa.|Faculty of Forestry and Forest Ecology, Georg-August-University Göttingen, Büsgenweg 5, D-37077, Göttingen, Germany.
authors: Klaus V
authors: KV
authors: Gadow
mesh_terms: D001419:Bacteria / Q000378:metabolism*; D018533:Biomass; D002245:Carbon Dioxide / Q000378:metabolism; D017753:Ecosystem; D065928:Forests; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D028223:Pinus / Q000254:growth & development* / Q000378:metabolism; D018517:Plant Roots / Q000254:growth & development / Q000378:metabolism; D012621:Seasons; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D009584:Nitrogen
keywords: Chinese pine forest; Interactive effect; Nitrogen supply; Organic matter treatment; Soil respiration