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| 1 | Data-driven estimates of global nitrous oxide emissions from croplands显示文摘Croplands are the single largest anthropogenic source of nitrous oxide(N2O) globally, yet their estimates remain difficult to verify when using Tier 1 and 3 methods of the Intergovernmental Panel on Climate Change(IPCC). Here, we re-evaluate global cropland-N2O emissions in 1961–2014, using N-rate-dependent emission factors(EFs) upscaled from 1206 field observations in 180 global distributed sites and high-resolution N inputs disaggregated from sub-national surveys covering 15593 administrative units. Our results confirm IPCC Tier 1 default EFs for upland crops in 1990–2014, but give a ~15% lower EF in 1961–1989 and a ~67% larger EF for paddy rice over the full period. Associated emissions(0.82 ±0.34 Tg N yr–1) are probably one-quarter lower than IPCC Tier 1 global inventories but close to Tier 3 estimates. The use of survey-based gridded N-input data contributes 58% of this emission reduction, the rest being explained by the use of observation-based non-linear EFs. We conclude that upscaling N2O emissions from site-level observations to global croplands provides a new benchmark for constraining IPCC Tier 1 and 3 methods. The detailed spatial distribution of emission data is expected to inform advancement towards more realistic and effective mitigation pathways. | Qihui Wang Feng Zhou Ziyin Shang Philippe Ciais Wilfried Winiwarter Robert B.Jackson Francesco N.Tubiello Greet Janssens-Maenhout Hanqin Tian Xiaoqing Cui Josep G.Canadell Shilong Piao Shu Tao | 2020 | National Science Review2020，7，2： | 7 |
| 2 | Empirical estimates of regional carbon budgets imply reduced global soil heterotrophic respiration显示文摘Resolving regional carbon budgets is critical for informing land-based mitigation policy.For nine regions covering nearly the whole globe,we collected inventory estimates of carbon-stock changes complemented by satellite estimates of biomass changes where inventory data are missing.The net land–atmospheric carbon exchange(NEE)was calculated by taking the sum of the carbon-stock change and lateral carbon fluxes from crop and wood trade,and riverine-carbon export to the ocean.Summing up NEE from all regions,we obtained a global‘bottom-up'NEE for net land anthropogenic CO_(2)uptake of–2.2±0.6 Pg C yr^(-1)consistent with the independent top-down NEE from the global atmospheric carbon budget during 2000–2009.This estimate is so far the most comprehensive global bottom-up carbon budget accounting,which set up an important milestone for global carbon-cycle studies.By decomposing NEE into component fluxes,we found that global soil heterotrophic respiration amounts to a source of CO_(2)of 39 Pg C yr^(-1)with an interquartile of 33–46 Pg C yr^(-1)—a much smaller portion of net primary productivity than previously reported. | Philippe Ciais Yitong Yao Thomas Gasser Alessandro Baccini Yilong Wang Ronny Lauerwald Shushi Peng Ana Bastos Wei Li Peter A.Raymond Josep G.Canadell Glen P.Peters Rob J.Andres Jinfeng Chang Chao Yue A.Johannes Dolman Vanessa Haverd Jens Hartmann Goulven Laruelle Alexandra G.Konings Anthony W.King Yi Liu Sebastiaan Luyssaert Fabienne Maignan Prabir K.Patra Anna Peregon Pierre Regnier Julia Pongratz Benjamin Poulter Anatoly Shvidenko Riccardo Valentini Rong Wang Grégoire Broquet Yi Yin Jakob Zscheischler Bertrand Guenet Daniel SGoll Ashley-P.Ballantyne Hui Yang Chunjing Qiu Dan Zhu | 2021 | National Science Review2021，8，2： | 3 |
| 3 | Estimating cropland carbon mitigation potentials in China affected by three improved cropland practices显示文摘Agriculture is a large source of carbon emissions. The cropland practices of fertilizer substitution, crop straw and conservation tillage are beneficial and help to rebuild local soil carbon stocks and reduce soil carbon emissions, in addition to reducing the consumption of fertilizers and fossil fuels. These improved cropland practices can directly and indirectly mitigatecarbon emissions, benefiting the sustainability of croplands. For these three improved practices, we estimated carbon mitigation potentials in rice, wheat and maize croplands in China. The combined contribution of these practices to carbon mitigation was 38.8 Tg C yr-1, with fertilizer substitution, crop straw return, and conservation tillage contributing 26.6, 3.6 and 8.6 Tg C yr-1, respectively. Rice, wheat and maize croplands had potentials to mitigate 13.4, 11.9 and 15.5 Tg C yr-1, respectively, with the combined direct and indirectpotential of 33.8 and 5.0 Tg C yr-1. Because of differences in local climate and specific diets, the regional cropland carbon mitigation potentials differed greatly among provinces in China. In China, 18 provinces had a 'target surplus' for which the carbon mitigation from these three practices was larger than the mitigation target set for 2020. At the national level, a net 'target surplus'of 4.84 Tg C yr-1 would be attained for Chinese croplands with full implementation of the three improved practices. Regional cooperation must be developed to achieve carbon mitigation targets using such measures as carbon trading, establishing regional associations, and strengthening research programs to improve practices. | LUN Fei Josep G.CANADELL HE Lu YANG Bo LIU Mou-cheng YUAN Zheng TIAN Mi LIU Jun-guo LI Wen-hua | 2016 | Journal of Mountain Science2016，13，10： | 1 |
| 4 | Annual Maps of Forests in Australia from Analyses of Microwave and Optical Images with FAO Forest Definition显示文摘The Australian governmental agencies reported a total of 149 million ha forest in the Food and Agriculture Organization of the United Nations(FAO)in 2010,ranking sixth in the world,which is based on a forest definition with tree height>2 meters.Here,we report a new forest cover data product that used the FAO forest definition(tree cover>10%and tree height>5 meters at observation time or mature)and was derived from microwave(Phased Array type L-band Synthetic Aperture Radar,PALSAR)and optical(Moderate Resolution Imaging Spectroradiometer,MODIS)images and validated with very high spatial resolution images,Light Detection and Ranging(LiDAR)data from the Ice,Cloud,and land Elevation Satellite(ICESat),and in situ field survey sites.The new PALSAR/MODIS forest map estimates 32 million ha of forest in 2010 over Australia.PALSAR/MODIS forest map has an overall accuracy of~95%based on the reference data derived from visual interpretation of very high spatial resolution images for forest and nonforest cover types.Compared with the canopy height and canopy coverage data derived from ICESat LiDAR strips,PALSAR/MODIS forest map has 73%of forest pixels meeting the FAO forest definition,much higher than the other four widely used forest maps(ranging from 36%to 52%).PALSAR/MODIS forest map also has a reasonable spatial consistency with the forest map from the National Vegetation Information System.This new annual map of forests in Australia could support cross-country comparison when using data from the FAO Forest Resource Assessment Reports. | Yuanwei Qin Xiangming Xiao Jean-Pierre Wigneron Philippe Ciais Josep G.Canadell Martin Brandt Xiaojun Li Lei Fan Xiaocui Wu Hao Tang Ralph Dubayah Russell Doughty Qing Chang Sean Crowell Bo Zheng Kevin Neal Jorge A.Celis Berrien MooreⅢ | 2021 | Journal of Remote Sensing2021，，1： | 0 |
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