title: The responses of soil respiration to nitrogen addition in a temperate grassland in northern China.
abstract: Anthropogenic activities have increased nitrogen (N) inputs to grassland ecosystems. Knowledge of the impact of soil N availability on soil respiration (RS) is critical to understand soil carbon balances and their responses to global climate change. A 2-year field experiment was conducted to evaluate the response of RS to soil mineral N in a temperate grassland in northern China. RS, abiotic and biotic factors, and N mineralization were measured in the grassland, at rates of N addition ranging from 0 to 25gNm(-2)yr(-1). Annual and dormant-season RS ranged from 241.34 to 283.64g C m(-2) and from 61.34 to 83.84g C m(-2) respectively. High N application significantly increased RS, possibly due to increased root biomass and increased microbial biomass. High N treatment significantly increased soil NO3-N and inorganic N content compared with the control. The ratio of NO3-N to NH4-N and the N mineralization rate were significantly positively correlated with RS, but NH4-N was not correlated or negatively correlated with RS during the growing season. The temperature sensitivity of RS (Q10) was not significantly affected by N levels, and ranged from 1.90 to 2.20, but decreased marginally significantly at high N. RS outside the growing season is an important component of annual RS, accounting for 25.0 to 29.6% of the total. High N application indirectly stimulated RS by increasing soil NO3-N and net nitrification, thereby eliminating soil N limitations, promoting ecosystem productivity, and increasing soil CO2 efflux. Our results show the importance of distinguishing between NO3-N and NH4-N, as their impact on soil CO2 efflux differed.
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Qinpu
authors.initials: Q
authors.lastname: Luo
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China. Electronic address: jrgong@bnu.edu.cn.
authors.forename: Jirui
authors.initials: J
authors.lastname: Gong
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Zhanwei
authors.initials: Z
authors.lastname: Zhai
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Pan
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Min
authors.initials: M
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Sha
authors.initials: S
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Yihui
authors.initials: Y
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Surface Processes and Resource Ecology, College of Resources Science and Technology, Beijing Normal University, Beijing 100875, PR China.
authors.forename: Lili
authors.initials: L
authors.lastname: Yang
authors.affiliation: College of Life Sciences, Inner Mongolia University, Hohhot 010021, PR China. Electronic address: bytgtnm@126.com.
authors.forename: Taoge-Tao
authors.initials: TT
authors.lastname: Baoyin
keywords: Grassland; Mineralization; Nitrogen addition; Q(10); Soil respiration