[HCG22-P01] Dynamics of water and carbon use efficiency of global croplands from 2000 to 2014
Keywords:Cropland, Water use efficiency, Carbon use efficiency, Global
Annual Moderate Resolution Imaging Spectroradiometer (MODIS) GPP, NPP, and ET data at a spatial resolution of around 1 km were obtained from the Numerical Terradynamic Simulation Group at the University of Montana. These products have been widely used in the research of WUE and CUE. Water use efficiency (WUE), here was calculated as the ratio of gross primary production (GPP) to evapotranspiration (ET), and carbon use efficiency (CUE), here was calculated as the ratio of net primary production (NPP) to gross primary production (GPP). The Global Food Security-support Analysis Data (GFSAD) product of crop dominance (GFSAD1KCD) at 1 km resolution was used to produce global cropland map. The least square estimation was used to quantify the variations of global cropland GPP, NPP, ET, WUE and CUE.
This study presented the temporal and spatial variation of water use efficiency (WUE) and carbon use efficiency (CUE) for croplands from 2000 to 2014 at a global scale for the first time. As for WUE, the highest value (mean around 1.92 g C kg-1 H2O) generally occurred in east America, Europe and southwest Canada. The lowest value (mean around 1.52 g C kg-1 H2O) occurred in India and China. As for CUE, the highest value (mean around 0.58) occurred in east America. The lowest value (mean around 0.44) generally occurred in tropical areas such as southeast Asia, east Brazil, and Africa. Moreover, a clear increasing trend of WUE was found in north China, India, east Africa, etc. On the contrary, a clear decreasing trend of WUE was found in middle area of south America, north Africa, northwest India, and southwest Russia. A clear increasing trend of CUE was found in the middle part of South America. On the contrary, a clear decreasing trend of CUE was found in southwest Russia, and some area in middle US and Argentina. This study gives new insights for better understanding the dynamics of global croplands' WUE and CUE. This study was supported by the project named Study on Multi-Scale Evaluation System for GHG Variation and Mitigation (1620AA011).