Chin J Plan Ecolo ›› 2014, Vol. 38 ›› Issue (6): 619-625.doi: 10.3724/SP.J.1258.2014.00057

• Research Articles • Previous Articles     Next Articles

Responses of soil respiration to reduced water table and nitrogen addition in an alpine wetland on the Qinghai-Xizang Plateau

WANG Hao1,2, YU Ling-Fei3, CHEN Li-Tong1, WANG Chao4, and HE Jin-Sheng1,4*   

  1. 1Key Laboratory of Adaptation and Evolution of Plateau Biota, Northwest Institute of Plateau Biology, Chinese Academy of Sciences, Xining 810008, China;

    2University of Chinese Academy of Sciences, Beijing 100049, China;

    3State Key Laboratory of Vegetation and Environmental Change, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China;

    4Key Laboratory for Earth Surface Processes of the Ministry of Education, Department of Ecology, College of Urban and Environmental Sciences, Peking University, Beijing 100871, China
  • Received:2014-01-20 Revised:2014-04-23 Online:2014-06-10 Published:2014-06-01
  • Contact: HE Jin-Sheng E-mail:jshe@pku.edu.cn

Abstract:

Aims Over the past 20 years, alpine wetlands have been subjected to a rapid change in climate, resulting in water table drawdown and increased nitrogen deposition. In wetland ecosystems, the water table drawdown can improve soil aeration, hence leading to a higher soil respiration rate; whereas an increased nitrogen deposition could reduce the microbial biomass and pH value, suppressing soil respiration. Understanding the responses of soil respiration to reduced water table and increased nitrogen deposition in alpine wetlands is thus critical to predicting the carbon cycle of wetland ecosystems and its feedbacks to ongoing climate changes. This study tests the effects of water table reduction and nitrogen addition on soil respiration in the Luanhaizi wetland on the Qinghai-Xizang Plateau.
Methods We imposed four treatments, including control (WT0 N0), reduced water table (WT N0), nitrogen addition (WT0 N+), and a combination of reduced water table and nitrogen addition (WT N+), on 20 peat monoliths collected from the Luanhaizi wetland at the Haibei station. Soil respiration was measured from late July through mid-September under all treatments.
Important findings A reduction in water table significantly increased the rate of soil respiration. In contrast, nitrogen addition suppressed soil respiration only when water table was not reduced. A positive correlation was found between the aboveground biomass and soil respiration, while no correlation was detected between root biomass and soil respiration. The temperature sensitivity of soil respiration was increased by reduced water table, but was not affected by nitrogen addition. Our results suggest that nitrogen deposition is likely to reduce soil CO2 emission in alpine wetlands where water level remains high. However, future warmer and drier conditions could result in reduced water table, and consequently alpine wetlands would be predicted to release substantially more CO2 than previously estimated.

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