Effects of warming and nitrogen fertilization on GHG flux in an alpine swamp meadow of a permafrost region

• Published in: Science of The Total Environment
• Main Authors: Chen, Xiaopeng, Wang, Genxu, Zhang, Tao, Mao, Tianxu, Wei, Da, Song, Chunlin, Hu, Zhaoyong, Huang, Kewei
• Format: Article in Journal/Newspaper
• Language: English
• Published: ELSEVIER SCIENCE BV 2017
• Subjects: Simulated Warming; Nitrogen Addition; Greenhouse Gas; Seasonal Variation; Science & Technology; Life Sciences & Biomedicine; Environmental Sciences & Ecology; QINGHAI-TIBETAN PLATEAU; FREEZE-THAW CYCLES; SOIL RESPIRATION; ECOSYSTEM RESPIRATION; N2O FLUXES; CLIMATE-CHANGE; TEMPERATURE SENSITIVITY; MICROBIAL COMMUNITIES; TIANSHAN MOUNTAINS; METHANE EMISSIONS; Environmental Sciences; permafrost
• Online Access: http://ir.imde.ac.cn/handle/131551/18960; https://doi.org/10.1016/j.scitotenv.2017.06.028

Uncertainties in the seasonal changes of greenhouse gases (GHG) fluxes in wetlands limit our accurate understanding of the responses of permafrost ecosystems to future warming and increased nitrogen (N) deposition. Therefore, in an alpine swamp meadow in the hinterland of the Qinghai-Tibet Plateau, a simulated warming with N fertilization experiment was conducted to investigate the key GHG fluxes (ecosystem respiration [Re], CH4 and N2O) in the early (EG), mid (MG) and late (LG) growing seasons. Results showed that warming (6.2 degrees C) increased the average seasonal Re by 30.9% and transformed the alpine swamp meadow from a N2O sink to a source, whereas CH4 flux was not significantly affected. N fertilization (4 g N m(-2) a(-1)) alone had no significant effect on the fluxes of GHGs. The interaction of warming and N fertilization increased CH4 uptake by 69.6% and N2O emissions by 26.2% compared with warming, whereas the Re was not significantly affected. During the EG, although the soil temperature sensitivity of the Re was the highest, the effect of warming on the Re was the weakest. The primary driving factor for Re was soil surface temperature, whereas soil moisture controlled CH4 flux, and the N2O flux was primarily affected by rain events. The results indicated: (i) increasing N deposition has both positive and negative feedbacks on GHG fluxes in response to climate warming; (ii) during soil thawing process at active layer, low temperature of deep frozen soils have a negative contribution to Re in alpine ecosystems; and (iii) although these alpine wetland ecosystems are buffers against increased temperature, their feedbacks on climate change cannot be ignored because of the large soil organic carbon pool and high temperature sensitivity of the Re. (C) 2017 Elsevier B.V. All rights reserved.