HR: 1340h
AN: B33D-1593 [Abstracts]
TI: Response of terrestrial vegetation to water and energy: the contribution of earth observation to
estimate and understand Water Use Efficiency at multiple scales
AU: * Menenti, M C
EM: mmenenti@yahoo.com
AF: Universite Louis Pasteur, 5 Blvd. Sebastien Brant, Illkirch, 67400, France
AU: * Menenti, M C
EM: mmenenti@yahoo.com
AF: School of Geography, Beijing Normal University, nr. 19 Xinjiekouwai Street, Beijing,
100875, China
AU: Jia, L
EM: Li.Jia@wur.nl
AF: Alterra - Wageningen University and Research Centre, Droevendaalsesteeg 3,
Wageningen, 6700 AA, Netherlands
AU: Jia, L
EM: Li.Jia@wur.nl
AF: School of Geography, Beijing Normal University, nr. 19 Xinjiekouwai Street, Beijing,
100875, China
AB:
Climate variability implies variable water availability and drought hazards in many parts of the world. Vegetation
species, especially taking into account significant biodiversity, react very differently to water scarcity. The amount
of biomass produced per unit volume of water transpired changes significantly across and within species,
according to genetic characteristics. The latter represent the most significant resource towards adaptation of
agriculture to climate change. On the other hand it remains difficult both to assess Water Use Efficiency (WUE) at
larger spatial scales and to model WUE in a way sufficiently simple to allow inclusion in the large area and global
climate models used to assess impacts and evaluate adaptation options. WUE is a ratio of extensive quantities
and provides directly an upscaling constraint for all variables involved in related parameterizations.
The first challenge is to observe WUE at any spatial scale larger than a single plant. At this scale biomass can be
determined by direct sampling and transpiration can be measured to a satisfactory level of accuracy with sap-
flow devices. At larger spatial scales no direct experimental method is available and heterogeneity makes
attribution of estimated total water flux to specific vegetation types within the area observed rather difficult. Use of
radiometric data collected from aircrafts and satellites is a practical approach to estimate and map both water flux
and biomass, thus leading to WUE. When using satellite data this approach makes frequent observations and
monitoring in time possible. This review presentation summarizes current approaches and trends in the
estimation of vegetation-atmosphere water exchange and of biomass. Analysis of time series of indicators of
vegetation response to water availability in terms of both ET and biomass will be presented on the basis of case-
studies in Africa, South America, Europe and China.
DE: 0315 Biosphere/atmosphere interactions (0426, 1610)
DE: 0480 Remote sensing
DE: 0495 Water/energy interactions (1878)
SC: Biogeosciences [B]
MN: 2007 Fall Meeting