Variability in growth, carbon isotope composition, leaf gas exchange and hydraulic traits in the eastern Mediterranean cedars Cedrus libani and C. brevifolia

Abstract

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 CO(2) assimilation (A), stomatal conductance (g(s)), (13)C isotope composition (delta(13)C), 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 delta(13)C and intrinsic water-use efficiency (A/g(s)), and negatively correlated with g(s). Drought reduced growth and favored carbon storage in roots, increasing the ratio of root biomass to aboveground biomass. The drought treatment increased delta(13)C and A/g(s). Specific hydraulic conductivity (K(s)) was similar for the provenance groups, whereas leaf-specific conductivity (K(l)) was lower in the Lebanese provenances than in the other provenances. Within each provenance group, provenances with the highest K(l) 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.

Carbon isotope discrimination and differential drought tolerance in eucalypt clones

“…The positive correlation between the values of δ 13 C and productivity has also been reported in other studies (SARRIS et al, 2013) and may be due to a lower stomata conductance associated with the maintenance of the photosynthetic rate by the tolerant clone (DUCREY et al, 2008). This suggests that this clone has mechanisms that provide a greater transpiration efficiency and hence higher productivity than the drought-sensitive one when growing in environments under severe water deficit.…”

“…Similar results were observed by Yin et al (2009), who found that conditions which favored better transpiration control of plants grown under limited water conditions contributed to lower δ 13 C and lower water content in the leaves of two tree species, Populus cathayana and P. przewalskii. These results contrast the woody plant literature (DaMATTA et al, 2003;DUCREY et al, 2008), which indicates that low Ψ wf leads to lower photosynthetic rates and consequently higher isotope discrimination, i.e. more negative values of δ 13 C. There were no significant differences between the δ 13 C values of leaf and wood samples ( Table 1), pointing that the 13 C signature in leaf or wood samples can be potentially used to assess the water stress.…”

Intraspecific variation and plasticity in growth and foliar morphology along a climate gradient in the Canary Island pine

“…Despite its small distribution area, topography, island colonization pattern and within island differentiation have favored a complex genetic structure and a high level of haplotypic diversity (Gómez et al 2003). The existence of genetic differentiation between populations is a key aspect of adaptation to different environments in forest trees (Bongarten and Teskey 1987;Ducrey et al 2008). Geographical variation in survival (López et al 2007), ontogeny and traits related to fire response (Climent et al 2004) of this species have been already assessed.…”

Stand structure and regeneration of Cedrus libani (A. Rich) in Tannourine Cedar Forest Reserve (Lebanon) affected by cedar web-spinning sawfly (Cephalcia tannourinensis, Hymenoptera: Pamphiliidae).

“…This seems to be clearly related to the higher number of young individuals and the lower DBH value of infested stands (DBH = 5.65 cm) compared to larger trees (DBH = 27 cm) in non-infested stands. The cedar of Lebanon is a light demanding species, but it is also characterized by its capability of surviving in partial shade during its early growth stages (Ducrey et al 2008), which explains the good regeneration status and the high number of young individuals in all stands. Furthermore, the loss of large trees in the infested plots after 1999 has created large canopy openings with high levels of light in the understory.…”