Seasonal responses of terrestrial ecosystem water‐use efficiency to climate change
- Sino‐French Institute for Earth System Science College of Urban and Environmental Sciences Peking University Beijing 100871 China
- Sino‐French Institute for Earth System Science College of Urban and Environmental Sciences Peking University Beijing 100871 China, Institute of Tibetan Plateau Research Chinese Academy of Sciences Beijing 100085 China
- Sino‐French Institute for Earth System Science College of Urban and Environmental Sciences Peking University Beijing 100871 China, LSCE UMR CEA‐CNRS Bat. 709, CE, L'Orme des Merisiers F‐91191 Gif‐sur‐Yvette France
- LSCE UMR CEA‐CNRS Bat. 709, CE, L'Orme des Merisiers F‐91191 Gif‐sur‐Yvette France
- CSIRO Land and Water Flagship GPO Box 1666 Canberra ACT 2601 Australia
- Climate Change Science Institute and Environmental Sciences Division Oak Ridge National Laboratory 1 Bethel Valley Road Oak Ridge TN 37831 USA
- Institute on Ecosystems and the Department of Ecology Montana State University Bozeman MT 59717 USA
- CSIRO Ocean and Atmosphere Flagship PMB 1 Aspendale Vic. 3195 Australia
Ecosystem water‐use efficiency ( EWUE ) is an indicator of carbon–water interactions and is defined as the ratio of carbon assimilation ( GPP ) to evapotranspiration ( ET ). Previous research suggests an increasing long‐term trend in annual EWUE over many regions and is largely attributed to the physiological effects of rising CO 2 . The seasonal trends in EWUE , however, have not yet been analyzed. In this study, we investigate seasonal EWUE trends and responses to various drivers during 1982–2008. The seasonal cycle for two variants of EWUE , water‐use efficiency ( WUE , GPP / ET ), and transpiration‐based WUE ( WUE t , the ratio of GPP and transpiration), is analyzed from 0.5° gridded fields from four process‐based models and satellite‐based products, as well as a network of 63 local flux tower observations. WUE derived from flux tower observations shows moderate seasonal variation for most latitude bands, which is in agreement with satellite‐based products. In contrast, the seasonal EWUE trends are not well captured by the same satellite‐based products. Trend analysis, based on process‐model factorial simulations separating effects of climate, CO 2 , and nitrogen deposition ( NDEP ), further suggests that the seasonal EWUE trends are mainly associated with seasonal trends of climate, whereas CO 2 and NDEP do not show obvious seasonal difference in EWUE trends. About 66% grid cells show positive annual WUE trends, mainly over mid‐ and high northern latitudes. In these regions, spring climate change has amplified the effect of CO 2 in increasing WUE by more than 0.005 gC m −2 mm −1 yr −1 for 41% pixels. Multiple regression analysis further shows that the increase in springtime WUE in the northern hemisphere is the result of GPP increasing faster than ET because of the higher temperature sensitivity of GPP relative to ET . The partitioning of annual EWUE to seasonal components provides new insight into the relative sensitivities of GPP and ET to climate, CO 2, and NDEP .
- Sponsoring Organization:
- USDOE
- Grant/Contract Number:
- AC05-00OR22725
- OSTI ID:
- 1400946
- Alternate ID(s):
- OSTI ID: 1346643
- Journal Information:
- Global Change Biology, Journal Name: Global Change Biology Journal Issue: 6 Vol. 22; ISSN 1354-1013
- Publisher:
- Wiley-BlackwellCopyright Statement
- Country of Publication:
- United Kingdom
- Language:
- English
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