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Harvard Forest Symposium Abstract 2005
- Title: DYNAMIC COUPLING OF STOMATA AND TREE HYDRAULICS
- Primary Author: Nathan Phillips (Boston University)
- Additional Authors: Michael Daley (Boston University)
- Abstract:
Water flux in vegetation shows substantial temporal variability that is
unrelated to variation in environmental drivers. Understanding the source
of this variation is needed for predicting canopy transpiration and
photosynthesis at the time resolution of current
soil-vegetation-atmosphere models. Two types of studies have examined this
problem. One body of work ("stomatal") has shown that oscillations in
transpiration may result from lags in water flow, turgor, and stomatal
response within leaves, but treats the hydraulic supply system in the stem
and branches as steady state. Another body of work ("hydraulic") has
examined how lags in stem and branch water flow affect supply of water to
leaves, but do not consider the lagged feedback response of stomata. In
each treatment (stomatal, hydraulic), the other factor (hydraulic,
stomatal) has been over-simplified. We have extended the simple leaf level
stomatal dynamics model of Cowan (1972) to integrate both stomatal and
stem hydraulic lags and their feedback. This model successfully predicts
time variation in whole tree water transport that is not accounted for by
environmental variation. This model provides insight into the internal
regulation of vegetation water flux and improves our ability to predict
tree and ecosystem carbon and water exchange on sub-diurnal time steps.
- Research Category:
