Water use of drought-tolerant coniferous trees ( Pinus brutia and
Cupressus sempervirens ) in a semi-arid environment
Abstract
Pinus brutia (pine) and Cupressus sempervirens (cypress)
are two important forestry species in the Mediterranean region, with
different strategies to cope with water stress. The overall goal of this
study is to investigate ecohydrological processes of these two species.
Specific objectives are: (i) to quantify their transpiration; (ii) to
analyze relations between meteorological variables, soil moisture, sap
flow, leaf conductance and twig water potential; and (iii) to assess
differences in soil water balances and dynamics between three canopy
cover conditions (under canopy, edge of canopy, open area). The study
site is a plantation forest in Athalassa Forest Park, in Cyprus with a
long-term average annual rainfall of 315 mm. The site was converted from
rainfed agriculture in 2011. Observations of sap flow (12 trees for 20
months, 4 trees for 24 months) and soil moisture (66 sensors, 24 months)
were made hourly. Soil moisture sensors were installed under the tree
canopy, at the edge of the canopy and in the open area at 10-, 30- and
50-cm soil depths. Mid-day twig water potential ( Ψ) and leaf
conductance ( gs) were measured monthly. The sap flow of cypress
trees was double that of pine. Pine seems to regulate its stomata and
shows less response to rainfall compared to cypress. Soil water balance
computations showed that evapotranspiration from the 60-cm soil depth of
the areas without tree canopy cover was higher than that of areas with
canopy cover, likely due to preferential flows caused by the tree canopy
and roots.