Inter- and intraspecific variations in bud phenology, foliar morphology, seasonal stomatal conductance and carbon isotopic composition in Cedrus libani and C. atlantica

Abstract

Afforestation and reforestation activities enjoy a prominent place on the policy agenda as potential tools to sequester carbon and for biomass production to mitigate climate change and restoring marginal lands. Two provenances (1 from Turkey and 1 from Lebanon) of the species Cedrus libani A. Rich. and two provenances (1 from Morocco and 1 from France) of the species Cedrus atlantica (Endl.) Carrier were studied to evaluate to what degree these trees were suitable for afforestation in arid regions of Italy. We measured, seasonal stomatal conductance (g s), foliar morphology, foliar carbon isotopic composition (δ13C), growth, and assessed bud phenology in a split plot trials. Bud phenology showed that the Turkish and Lebanon provenances of C. libani gave rise to earlier buds (earlier bud provenances) than the Moroccan and French provenances of C. atlantica (later bud provenances) with a mean difference of 23.2 days. Both provenances showed similar bud phenology and seasonal stomatal conductance (g s) especially in April–May (earlier bud provenances) and June (later bud provenances). The foliar δ13C was negatively correlated with g s in both the earlier bud provenances (i.e., an increase in g s was accompanied by decreasing foliar δ13C values) and the later bud provenances. The stomatal conductance values measured over a growth season showed significant correlations with daily means of both temperature and relative humidity. Hence g s in the earlier bud provenances was correlated with daily temperature in spring, whereas correlations with relative humidity were found in later bud provenances in both late spring and summer. We concluded that the earlier bud provenances (C. libani) are not suitable in areas affected by both summer drought and late spring frosts, whereas the later bud provenances (C. atlantica) are more suitable to be used in future afforestation plans due to their greater tolerance to summer drought.