Variability in growth, carbon isotope composition, leaf gas exchange and hydraulic traits in the eastern Mediterranean cedars
Cedrus libani and C. brevifolia
M. Ducrey (1), R. Huc (1, 2, 3), M. Ladjal (1) and J.-M. Guehl (2)
1. INRA, UR629 Recherches Forestières Méditerranéennes, F-84000 Avignon, France / 2. INRA, UMR1137 Ecologie et Ecophysiologie Forestières, F-54280 Champenoux, France / 3. Corresponding author () / Received June 27, 2007; accepted October 25, 2007; published online March 3, 2008
Summary
Four Turkish provenances and five Lebanese provenances of Cedrus libani A. Rich. and one Cypriot provenance of C. brevifolia Henry were compared during the third year of growth in a controlled-climate greenhouse after exposure to a well-watered or
moderate-drought treatment. Effects of treatment on CO2 assimilation (A), stomatal conductance (gs), 13C isotope composition (δ13C), growth and biomass were assessed. Hydraulic conductivity and shoot vulnerability to cavitation were measured in well-watered
plants only. The Lebanese provenances of C. libani had the highest growth rates, but were the most sensitive to drought. The Turkish provenances of C. libani showed moderate growth rates and moderate drought sensitivity. Cedrus brevifolia had the lowest growth rate and was least sensitive to drought. For each provenance, mean biomass values were positively correlated
with δ13C and intrinsic water-use efficiency (A/gs), and negatively correlated with gs. Drought reduced growth and favored carbon storage in roots, increasing the ratio of root biomass to aboveground biomass.
The drought treatment increased δ13C and A/gs. Specific hydraulic conductivity (Ks) was similar for the provenance groups, whereas leaf-specific conductivity (Kl) was lower in the Lebanese provenances than in the other provenances. Within each provenance group, provenances with the
highest Kl were most susceptible to xylem cavitation, but were also the most productive. Growth and drought adaptation were linked with
precipitation in each provenance’s native range.
Keywords:
biomass, ecotype variation, hydraulic conductivity, net CO2 assimilation, stomatal conductance, water-use efficiency.
