 |
| Titel |
Atmospheric constraints on Plant Water Use Efficiency drivers and patterns of changes since 1900 |
| VerfasserIn |
Margriet Groenendijk, Peter Cox, Ben Booth, Hugo Lambert |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250074317
|
|
|
|
|
|
| Zusammenfassung |
| Water Use Efficiency (WUE) controls the relationship between the ecosystem water and
carbon balance. Because WUE responds to environmental changes it can be used as a metric
to quantify the effect of climate change on ecosystems. The actual WUEeco is defined as a
ratio of gross primary production and transpiration fluxes. On the leaf scale this is
equal to the atmospheric WUEatm, which is a function of the ambient and internal
CO2 concentration, the saturated specific humidity and relative humidity. Using
observations and the JULES and HadCM3 models we explore on which temporal and
spatial scales WUEeco and WUEatm are equal, and how they respond to climate
change.
Leaf level definitions are valid at site level, where annual WUEeco and WUEatm
simulated with JULES are equal and linearly increasing with atmospheric CO2
concentration for a range of sites. For drier sites lower values of both were simulated. The
simulated values are within the same range as values derived from eddy covariance
observations.
Having shown the near equivalence between WUEeco and WUEatm for specific sites, we
can use the formula for WUEatm to estimate the change in plant WUE over the 20th
century, using observed climatological data and CO2 concentrations. In general
WUE is found to increase strongly with the CO2 concentration, but this is offset
by warming and drying that increases evaporative demand and therefore reduces
WUE.
As a result we find complex spatio-temporal patterns of changes in WUE, resulting from
the differing drivers of climate change and variation. For example, warming due to the
reduction in atmospheric aerosol pollution since the late 1980s reduced WUE in some
previously heavily-polluted regions despite the ongoing increase in atmospheric CO2. We
will describe the methods used to reconstruct WUE from observations, and discuss the spatial
and temporal variation of WUE since 1900. |
|
|
|
|
|
|