Global Nitrous Oxide Emissions From Pasturelands and Rangelands: Magnitude, Spatiotemporal Patterns, and Attribution

Abstract The application of manure and mineral nitrogen (N) fertilizer, and livestock excreta deposition are the main drivers of nitrous oxide (N 2 O) emissions in agricultural systems. However, the magnitude and spatiotemporal variations of N 2 O emissions due to different management practices (excreta deposition and manure/fertilizer application) from grassland ecosystems remain unclear. In this study, we used the Dynamic Land Ecosystem Model to simulate the spatiotemporal variation in global N 2 O emissions and their attribution to different sources from both intensively managed ( pasturelands ) and extensively managed ( rangelands ) grasslands during 1961–2014. Over the study period, pasturelands and rangelands experienced a significant increase in N 2 O emissions from 1.74 Tg N 2 O‐N in 1961 to 3.11 Tg N 2 O‐N in 2014 ( p < 0.05). Globally, pasturelands and rangelands were responsible for 54% (2.2 Tg N 2 O‐N) of the total agricultural N 2 O emissions (4.1 Tg N 2 O‐N) in 2006. Natural and anthropogenic sources contributed 26% (0.64 Tg N 2 O‐N/year) and 74% (1.78 Tg N 2 O‐N/year) of the net emissions, respectively. Across different biomes, pasturelands (i.e., C3 and C4) were the single largest contributor to N 2 O fluxes, accounting for 86% of the net global emissions from grasslands. Among different sources, livestock excreta deposition contributed 54% of the net emissions, followed by manure N (13%) and mineral N (7%) application. Regionally, southern Asia contributed 38% of the total emissions, followed by Europe (29%) and North America (16%). Our modeling study demonstrates that livestock excreta deposition and manure/fertilizer application have dramatically altered the N cycle in pasturelands, with a substantial impact on the climate system.