Terrestrial water fluxes dominated by transpiration
- 3 April 2013
- journal article
- Published by Springer Science and Business Media LLC in Nature
- Vol. 496 (7445), 347-350
- https://doi.org/10.1038/nature11983
Abstract
Renewable fresh water over continents has input from precipitation and losses to the atmosphere through evaporation and transpiration. Global-scale estimates of transpiration from climate models are poorly constrained owing to large uncertainties in stomatal conductance and the lack of catchment-scale measurements required for model calibration, resulting in a range of predictions spanning 20 to 65 per cent of total terrestrial evapotranspiration (14,000 to 41,000 km(3) per year) (refs 1, 2, 3, 4, 5). Here we use the distinct isotope effects of transpiration and evaporation to show that transpiration is by far the largest water flux from Earth's continents, representing 80 to 90 per cent of terrestrial evapotranspiration. On the basis of our analysis of a global data set of large lakes and rivers, we conclude that transpiration recycles 62,000 ± 8,000 km(3) of water per year to the atmosphere, using half of all solar energy absorbed by land surfaces in the process. We also calculate CO2 uptake by terrestrial vegetation by connecting transpiration losses to carbon assimilation using water-use efficiency ratios of plants, and show the global gross primary productivity to be 129 ± 32 gigatonnes of carbon per year, which agrees, within the uncertainty, with previous estimates. The dominance of transpiration water fluxes in continental evapotranspiration suggests that, from the point of view of water resource forecasting, climate model development should prioritize improvements in simulations of biological fluxes rather than physical (evaporation) fluxes.Keywords
This publication has 27 references indexed in Scilit:
- Water-Use Efficiency of the Terrestrial Biosphere: A Model Analysis Focusing on Interactions between the Global Carbon and Water CyclesJournal of Hydrometeorology, 2012
- Terrestrial Gross Carbon Dioxide Uptake: Global Distribution and Covariation with ClimateScience, 2010
- Importance of carbon dioxide physiological forcing to future climate changeProceedings of the National Academy of Sciences of the United States of America, 2010
- Simulations of global evapotranspiration using semiempirical and mechanistic schemes of plant hydrologyGlobal Biogeochemical Cycles, 2009
- The Partitioning of Evapotranspiration into Transpiration, Soil Evaporation, and Canopy Evaporation in a GCM: Impacts on Land–Atmosphere InteractionJournal of Hydrometeorology, 2007
- Contemporary “green” water flows: Simulations with a dynamic global vegetation and water balance modelPhysics and Chemistry of the Earth, Parts A/B/C, 2005
- Evapotranspiration components determined by stable isotope, sap flow and eddy covariance techniquesAgricultural and Forest Meteorology, 2004
- Estimates of Freshwater Discharge from Continents: Latitudinal and Seasonal VariationsJournal of Hydrometeorology, 2002
- Fluxes of CO2 and water between terrestrial vegetation and the atmosphere estimated from isotope measurementsNature, 1996
- Determining water use by trees and forests from isotopic, energy balance and transpiration analyses: the roles of tree size and hydraulic liftTree Physiology, 1996