Changes in aboveground structure and resistances to water uptake in Quercus coccifera along a rainfall gradient

Abstract

We have assumed that changes in Quercus coccifera canopies along a rainfall gradient can be understood in terms of a system which optimizes net photosynthesis while minimizing water loss. This optimization process leads to perceptible differences in branch and leaf display patterns (Aber et al. 1982). The observed differences can be interpreted as drought-related adaptation mechanisms (Miller 1983) or due to modifications in the carbon allocation scheme. We further have assumed that stands on drier sites which undergo greater water stress should have low leaf area indices, while those on mesic sites should exhibit a tendency towards tall canopies with high leaf area indices. Our third assumption has been that changes in canopy structure will be accompanied by changes in rooting depth. In our case, the rooting depth is indirectly determined by measuring water uptake resistances, i.e. plant and soil resistances.