Change in terrestrial ecosystem water-use efficiency over the last three decades

Mengtian Huang, Shilong Piao, Yan Sun, Philippe Ciais, Lei Cheng, Jiafu Mao, Ben Poulter, Xiaoying Shi, Zhenzhong Zeng, Yingping Wang
2015 Global Change Biology  
et al.. Change in terrestrial ecosystem water-use efficiency over the last three decades. Abstract 4 Defined as the ratio between gross primary productivity (GPP) and evapotranspiration (ET), 5 ecosystem-scale water-use efficiency (EWUE) is an indicator of the adjustment of vegetation 6 photosynthesis to water loss. The processes controlling EWUE are complex and reflect both a 7 slow evolution of plants and plant communities as well as fast adjustments of ecosystem 8 functioning to changes of
more » ... miting resources. In this study, we investigated EWUE trends from 9 1982 to 2008 using data-driven models derived from satellite observations, and 10 process-oriented carbon cycle models. Our findings suggest positive EWUE trends of 0.0056, 11 0.0007 and 0.0001 g C m -2 mm -1 yr -1 under the single effect of rising CO 2 ('CO 2 '), climate 12 change ('CLIM') and nitrogen deposition ('NDEP'), respectively. Global patterns of EWUE 13 trends under the different scenarios suggest that: (i) EWUE-CO 2 shows global increases, (ii) 14 EWUE-CLIM increases in mainly high latitudes and decreases at middle and low latitudes, 15 (iii) EWUE-NDEP displays slight increasing trends except in west Siberia, eastern Europe, 16 parts of North America and central Amazonia. The data-driven MTE model, however, shows a 17 slight decline of EWUE during the same period (-0.0005 g C m -2 mm -1 yr -1 ), which differs 18 from process-models (0.0064 g C m -2 mm -1 yr -1 ) simulations with all drivers are taken into 19 account. We attribute this discrepancy to the fact that the non-modeled physiological effects 20 of elevated CO 2 reducing stomatal conductance and transpiration (TR) in the MTE model. 21 Partial correlation analysis between EWUE and climate drivers shows similar responses to 22 climatic variables with the data-driven model and the process-oriented models across different 23 ecosystems. Change in water-use efficiency defined from transpiration-based WUE t (GPP/TR) 24 and inherent water-use efficiency IWUE t (GPP×VPD/ET) in response to rising CO 2
doi:10.1111/gcb.12873 pmid:25612078 fatcat:yzs6irce3vd7hmdi7yunam3o54