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 re...

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Bibliographic Details
Published in:Global biogeochemical cycles 2009-06, Vol.23 (2), p.GB2018-n/a
Main Authors: Beer, C, Ciais, P, Reichstein, M, Baldocchi, D, Law, B.E, Papale, D, Soussana, J.F, Ammann, C, Buchmann, N, Frank, D, Gianelle, D, Janssens, I.A, Knohl, A, Köstner, B, Moors, E, Roupsard, O
Format: Article
Language:English
Subjects:
Animal and plant ecology
Animal, plant and microbial ecology
aspen forest
atmosfeer
atmosphere
beech forest
Biogeosciences
Biological and medical sciences
canopy-scale
carbon cycle
Carbon cycling
carbon dioxide
central germany
Climatology
co2 exchange
coniferous forests
deciduous forests
Earth sciences
Earth, ocean, space
ecosystems
Ecosystems, structure and dynamics
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
Plant ecology
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
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Summary: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.
ISSN:0886-6236
1944-9224
1944-8224
DOI:10.1029/2008GB003233