The influence of site characteristics on the leaf-to-sapwood area relationship in chestnut trees (Castanea sativa Mill.)

Abstract

Biomass allocation in Castanea sativa varies according to the environmental conditions. Specifically, leaf-to-sapwood area ratio is higher on sites with good water supplies and lower in water-stressed conditions. Ecological plasticity allows organisms to adapt and to cope with environmental conditions. This is a key trait for species with long live span, which will probably be more vulnerable to changing climate because of their lower adaptation potential via natural selection. We studied the case of the sweet chestnut tree, a naturalized forest species in many European mountain areas, where it grows on very different climates and sites. This raises the question of its adaptation capacity to very different environmental conditions. To test this hypothesis, we applied the pipe model approach for analysing the variation in the leaf-to-sapwood area ratio (A L:A S) in 82 chestnut trees growing in very different site conditions (e.g., water-stressed convex vs. water-rich concave sites). We used linear regression analyses to model the A L:A S relationship to environmental and dendrometric parameters. Results confirm that A L:A S is significantly higher when trees grow on good nutrient- and water-supplied concave sites with respect to water-stressed, convex sites. Chestnut trees are thus able to vary their biomass allocation between sapwood and leaves to adapt their hydraulic characteristics to the site conditions. Trees seem to react to water-stressed conditions by allocating more biomass in the sapwood in respect to the leaves. A L:A S may thus represent a useful indicator of tree species plasticity and their adaptation potential to different environmental and climate conditions.