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|Title: ||Water-use strategies in two co-occurring Mediterranean evergreen oaks: surviving the summer drought|
|Authors: ||David, T.S.|
|Keywords: ||canopy conductance|
leaf water potential
|Issue Date: ||2007|
|Publisher: ||Heron Publishing|
|Citation: ||Tree Physiology 27, 793–803|
|Abstract: ||In the Mediterranean evergreen oakwoodlands of
southern Portugal, the main tree species are Quercus ilex ssp.
rotundifolia Lam. (holm oak) and Quercus suber L. (cork oak).
We studied a savannah-type woodland where these species coexist,
with the aim of better understanding the mechanisms of
tree adaptation to seasonal drought. In both species, seasonal
variations in transpiration and predawn leaf water potential
showed a maximum in spring followed by a decline through the
rainless summer and a recovery with autumn rainfall. Although
the observed decrease in predawn leaf water potential in summer
indicates soil water depletion, trees maintained transpiration
rates above 0.7 mm day–1 during the summer drought. By
that time, more than 70% of the transpired water was being
taken from groundwater sources. The daily fluctuations in soil
water content suggest that some root uptake of groundwater
was mediated through the upper soil layers by hydraulic lift.
During the dry season, Q. ilex maintained higher predawn leaf
water potentials, canopy conductances and transpiration rates
than Q. suber. The higherwater status of Q. ilexwas likely associated
with their deeper root systems compared with Q. suber.
Whole-tree hydraulic conductance and minimum midday leaf
water potential were lower in Q. ilex, indicating that Q. ilex was
more tolerant to drought than Q. suber. Overall, Q. ilex seemed
to have more effective drought avoidance and drought tolerance
mechanisms than Q. suber.|
|Appears in Collections:||BIO - Publicações - Artigos em Revistas Internacionais Com Arbitragem Científica|
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