Effects of grazing on CO 2 balance in a semiarid steppe: field observations and modeling
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SOILS, SEC 2 • GLOBAL CHANGE, ENVIRON RISK ASSESS, SUSTAINABLE LAND USE • RESEARCH ARTICLE
Effects of grazing on CO2 balance in a semiarid steppe: field observations and modeling Xiaoming Kang & Yanbin Hao & Xiaoyong Cui & Huai Chen & Changsheng Li & Yichao Rui & Jianqing Tian & Paul Kardol & Lei Zhong & Jinzhi Wang & Yanfen Wang
Received: 23 October 2012 / Accepted: 25 February 2013 / Published online: 14 March 2013 # Springer-Verlag Berlin Heidelberg 2013
P. Kardol Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, 90183, Umeå, Sweden
model (denitrification–decomposition) to investigate the impacts of grazing on the long-term C budget of semiarid grasslands. Materials and methods NEE measurements were conducted in two adjacent grassland sites, non-grazing (NG) and moderate grazing (MG), during 2006–2007. We then used daily weather data for 1978–2007 in conjunction with soil properties and grazing scenarios as model inputs to simulate grassland productivity and C dynamics. The observed and simulated CO2 fluxes under moderate grazing intensity were compared with those without grazing. Results and discussion NEE data from 2-year observations showed that moderate grazing significantly decreased grassland ecosystem CO2 release and shifted the ecosystem from a negative CO2 balance (releasing 34.00 g Cm−2) at the NG site to a positive CO2 balance (absorbing −43.02 g Cm−2) at the MG site. Supporting our experimental findings, the 30year simulation also showed that moderate grazing significantly enhances the CO2 uptake potential of the targeted grassland, shifting the ecosystem from a negative CO2 balance (57.08±16.45 g Cm−2 year−1) without grazing to a positive CO2 balance (−28.58 ± 14.60 g C m−2 year−1) under moderate grazing. The positive effects of grazing on CO2 balance could primarily be attributed to an increase in productivity combined with a significant decrease of soil heterotrophic respiration and total ecosystem respiration. Conclusions We conclude that moderate grazing prevails over no-management practices in maintaining CO2 balance in semiarid grasslands, moderating and mitigating the negative effects of global climate change on the CO2 balance in grassland ecosystems.
J. Wang Chinese Research Academy of Environmental Sciences, Beijing 100012, People’s Republic of China
Keywords Carbon budget . DNDC . Eddy covariance . Grassland . Grazing . Soil heterotrophic respiration
Abstract Purpose Carbon (C) dynamics in grassland ecosystem contributes to regional and global fluxes in carbon dioxide (CO2) concentrations. Grazing is one of the main structuring factors in grassland, but the impact of grazing on the C budget is still under debate. In this study, in situ net ecosystem CO2 exchange (NEE) observations by the eddy covariance technique were integrated with a modified process-oriented biogeochemistry
Responsible editor: Hailong Wang X. Kang : Y. Hao : X. Cui (*) : L. Zhong : Y. Wang (*) College of Life Sciences, University of Chinese Academy of Sciences, Beijing 1000
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