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  • 11
    Publication Date: 2022-05-25
    Description: © IOP Publishing, 2012. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Environmental Research Letters 7 (2012): 044020, doi:10.1088/1748-9326/7/4/044020.
    Description: Chemical nitrogen (N) fertilizer has long been used to help meet the increasing food demands in China, the top N fertilizer consumer in the world. Growing concerns have been raised on the impacts of N fertilizer uses on food security and climate change, which is lack of quantification. Here we use a carbon–nitrogen (C–N) coupled ecosystem model, to quantify the food benefit and climate consequence of agronomic N addition in China over the six decades from 1949 to 2008. Results show that N fertilizer-induced crop yield and soil C sequestration had reached their peaks, while nitrous oxide (N2O) emission continued rising as N was added. Since the early 2000s, stimulation of excessive N fertilizer uses to global climate warming through N2O emission was estimated to outweigh their climate benefit in increasing CO2 uptake. The net warming effect of N fertilizer uses, mainly centered in the North China Plain and the middle and lower reaches of Yangtze River Basin, with N2O emission completely counteracting or even exceeding, by more than a factor of 2, the CO2 sink. If we reduced the current N fertilizer level by 60% in 'over-fertilized' areas, N2O emission would substantially decrease without significantly influencing crop yield and soil C sequestration.
    Description: This study has been supported by NASA IDS Program (NNG04GM39C), NASA LCLUC Program (NNX08AL73G), and the National Basic Research Program of China (2010CB950900) and (2010CB950604).
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/pdf
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  • 12
    Publication Date: 2022-05-26
    Description: Author Posting. © American Geophysical Union, 2011. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Global Biogeochemical Cycles 25 (2011): GB1007, doi:10.1029/2010GB003838.
    Description: The magnitude, spatial, and temporal patterns of the terrestrial carbon sink and the underlying mechanisms remain uncertain and need to be investigated. China is important in determining the global carbon balance in terms of both carbon emission and carbon uptake. Of particular importance to climate-change policy and carbon management is the ability to evaluate the relative contributions of multiple environmental factors to net carbon source and sink in China's terrestrial ecosystems. Here the effects of multiple environmental factors (climate, atmospheric CO2, ozone pollution, nitrogen deposition, nitrogen fertilizer application, and land cover/land use change) on net carbon balance in terrestrial ecosystems of China for the period 1961–2005 were modeled with newly developed, detailed historical information of these changes. For this period, results from two models indicated a mean land sink of 0.21 Pg C per year, with a multimodel range from 0.18 to 0.24 Pg C per year. The models' results are consistent with field observations and national inventory data and provide insights into the biogeochemical mechanisms responsible for the carbon sink in China's land ecosystems. In the simulations, nitrogen deposition and fertilizer applications together accounted for 61 percent of the net carbon storage in China's land ecosystems in recent decades, with atmospheric CO2 increases and land use also functioning to stimulate carbon storage. The size of the modeled carbon sink over the period 1961–2005 was reduced by both ozone pollution and climate change. The modeled carbon sink in response to per unit nitrogen deposition shows a leveling off or a decline in some areas in recent years, although the nitrogen input levels have continued to increase.
    Description: This study has been supported by NASA IDS Program (NNG04GM39C), NASA LCLUC Pr o g ram (NNX08AL73G_S01), and China’s Ministry of Science and Technology (MOST) 973 Program (2002CB412500).
    Keywords: China ; Terrestrial carbon sink ; Ecosystem model
    Repository Name: Woods Hole Open Access Server
    Type: Article
    Format: application/msword
    Format: application/pdf
    Format: text/plain
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  • 13
    Publication Date: 2022-05-26
    Description: Author Posting. © The Author(s), 2015. This is the author's version of the work. It is posted here by permission of Nature Publishing Group for personal use, not for redistribution. The definitive version was published in Nature 531 (2016): 225-228, doi:10.1038/nature16946.
    Description: The terrestrial biosphere can release or absorb the greenhouse gases, carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) and therefore plays an important role in regulating atmospheric composition and climate1. Anthropogenic activities such as land use change, agricultural and waste management have altered terrestrial biogenic greenhouse gas fluxes and the resulting increases in methane and nitrous oxide emissions in particular can contribute to climate warming2,3. The terrestrial biogenic fluxes of individual greenhouse gases have been studied extensively4-6, but the net biogenic greenhouse gas balance as a result of anthropogenic activities and its effect on the climate system remains uncertain. Here we use bottom-up (BU: e.g., inventory, statistical extrapolation of local flux measurements, process-based modeling) and top-down (TD: atmospheric inversions) approaches to quantify the global net biogenic greenhouse gas balance between 1981-2010 as a result of anthropogenic activities and its effect on the climate system. We find that the cumulative warming capacity of concurrent biogenic CH4 and N2O emissions is about a factor of 2 larger than the cooling effect resulting from the global land CO2 uptake in the 2000s. This results in a net positive cumulative impact of the three GHGs on the planetary energy budget, with a best estimate of 3.9±3.8 Pg CO2 eq/yr (TD) and 5.4±4.8 Pg CO2 eq/yr (BU) based on the GWP 100 metric (global warming potential on a 100-year time horizon). Our findings suggest that a reduction in agricultural CH4 and N2O emissions in particular in Southern Asia may help mitigate climate change.
    Description: This research has been supported partially by National Aeronautics and 255 Space Administration (NASA) Grants (NNX08AL73G, NNX14AO73G, NNX10AU06G, NNX11AD47G, NNG04GM39C), National Science Foundation (NSF) Grants (CNH1210360; AGS 1243232; AGS-1243220). JGC was supported by the Australian Climate Change Science Program. ES was supported by NOAA Climate Program Office (award # NA13OAR4310059). CRS was supported by NASA Grants (#NNX12AP74G, #NNX10AG01A, and #NNX11AO08A). KRG was supported by NSF CAREER (AGS-0846358). RGP was supported by NASA Upper Atmosphere Research Program AGAGE Grant (NNX11AF17G to MIT).
    Description: 2016-09-09
    Repository Name: Woods Hole Open Access Server
    Type: Preprint
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