Journal Article

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

Papale, D, Frank, D, Law, B.E, Ammann, C, Köstner, B, Beer, C, Baldocchi, D, Knohl, A, Ciais, P, Buchmann, N, Roupsard, O, Moors, E, Reichstein, M, Soussana, J.F, Janssens, I.A, Gianelle, D

2009

Overview

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 climatic conditions. IWUE* increases during short‐term moderate drought conditions. Mean annual IWUE* varied by a factor of 3 among all sites. This is partly explained by soil moisture at field capacity, particularly in deciduous broad‐leaved forests. Canopy light interception sets the upper limits to canopy photosynthesis, and explains half the variance in annual IWUE* among herbaceous ecosystems and evergreen needle‐leaved forests. Knowledge of IWUE* offers valuable improvement to the representation of carbon and water coupling in ecosystem process models.

• Publisher: Blackwell Publishing Ltd,American Geophysical Union
• Subject: Animal and plant ecology / Animal, plant and microbial ecology / aspen forest / atmosfeer / atmosphere / beech forest / Biological and medical sciences / canopy-scale / carbon cycle / carbon dioxide / central germany / Climatology / co2 exchange / coniferous forests / deciduous forests / Earth sciences / Earth, ocean, space / ecosystems / eddy covariance / evapotranspiration / Exact sciences and technology / FLUXNET / forest ecosystems / Fundamental and applied biological sciences. Psychology / gas exchange / General aspects / Geochemistry / grasslands / gross primary production / inherent water use efficiency / Klimatologie / kooldioxide / koolstofcyclus / Life Sciences / photosynthesis / plants / ponderosa pine / primary productivity / Sciences of the Universe / scots pine forest / Synecology / temporal variation / terrestrial ecosystems / terrestrische ecosystemen / time scales / vegetation / water use efficiency / water vapor / water vapour movement / waterdampbeweging / watergebruiksrendement / wetlands