Temporal and among‐site variability of inherent water use efficiency at the ecosystem level

Half‐hourly measurements of the net exchanges of carbon dioxide and water vapor between terrestrial ecosystems and the atmosphere provide estimates of gross primary production (GPP) and evapotranspiration (ET) at the ecosystem level and on daily to annual timescales. The ratio of these quantities represents ecosystem water use efficiency. Its multiplication with mean daylight vapor pressure deficit (VPD) leads to a quantity which we call “inherent water use efficiency” (IWUE*). The dependence of IWUE* on environmental conditions indicates possible adaptive adjustment of ecosystem physiology in response to a changing environment. IWUE* is analyzed for 43 sites across a range of plant functional types and…

• NS
  National Science Foundation
• UD
  U.S. Department of Energy
• MR
  Microsoft Research
• UO
  University of Virginia
• UD
  Università degli Studi della Tuscia
• OO
  Office of Science
• OR
  Oak Ridge National Laboratory
• LB
  Lawrence Berkeley National Laboratory