Effects of six years of simulated N deposition on gross soil N transformation rates in an old-growth temperate forest  

作　　者：Peng Tian Jinbo Zhang Christoph Müller Zucong Cai Guangze Jin 

机构地区：[1]College of Forestry,Northeast Forestry University,Harbin 150040,Heilongjiang,People’s Republic of China [2]School of Geography Sciences,Nanjing Normal University,Nanjing 210023,People’s Republic of China [3]Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application,Nanjing 210023,People’s Republic of China [4]Department of Plant Ecology(IFZ),Justus-Liebig University Giessen,Heinrich-Buff-Ring 26,35392 Giessen,Germany [5]School of Biology and Environmental Science,University College Dublin,Dublin,Ireland

出　　处：《Journal of Forestry Research》2018年第3期644-653,共10页林业研究（英文版）

基　　金：supported by Grants from the ‘‘973’’ Project(2014CB953803);the Fundamental Research Funds for the Central Universities(2572017EA02);the Priority Academic Program Development of Jiangsu Higher Education Institutions(PAPD,164320H116)

摘　　要：Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing’an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory usingN tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH~+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO~-) was primarily produced via oxidation of NH~+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO~- consumption rates,resulting in a build-up of NO~-, which highlights the high risk of N losses via NO~- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.Elevated atmospheric nitrogen(N) deposition has been detected in many regions of China, but its effects on soil N transformation in temperate forest ecosystems are not well known. We therefore simulated N deposition with four levels of N addition rate(N0, N30, N60, and N120) for6 years in an old-growth temperate forest in Xiaoxing'an Mountains in Northeastern China. We measured gross N transformation rates in the laboratory using ^(15)N tracing technology to explore the effects of N deposition on soil gross N transformations taking advantage of N deposition soils. No significant differences in gross soil N transformation rates were observed after 6 years of N deposition with various levels of N addition rate. For all N deposition soils, the gross NH_4^+ immobilization rates were consistently lower than the gross N mineralization rates,leading to net N mineralization. Nitrate(NO_3^-) was primarily produced via oxidation of NH_4^+(i.e., autotrophic nitrification), whereas oxidation of organic N(i.e., heterotrophic nitrification) was negligible. Differences between the quantity of ammonia-oxidizing bacteria and ammonia-oxidizing archaea were not significant for any treatment, which likely explains the lack of a significant effect on gross nitrification rates. Gross nitrification rates were much higher than the total NO_3^- consumption rates,resulting in a build-up of NO_3^-, which highlights the high risk of N losses via NO_3^- leaching or gaseous N emissions from soils. This response is opposite that of typical N-limited temperate forests suffering from N deposition,suggesting that the investigated old-growth temperate forest ecosystem is likely to approach N saturation.

关 键 词：N deposition Gross soil N transformation Temperate forest ecosystem ^(15)N tracing technology 

分 类 号：S7[农业科学—林学]