View article

Tree species from upper Rio Negro rain forests (tierra firme, tall Amazon caatinga, and bana) can be classified morphologically as sclerophylls. In some cases, as for Clusia spp., the structural characteristics fit the pachyphyll leaf type of Grubb. Nutrient content, specific leaf area, and leaf thickness of the species studied are comparable to those of sclerophylls from Mediterranean climates. In spite of their sclerophyllous structure, leaves of the species studied are relatively drought intolerant. During rainless periods leaf stomatal conductance decreases markedly avoiding development of large negative xylem pressures. Overheating is prevented by most species through pronounced leaf surface inclination. It is concluded that sclerophyllous structure is not necessarily an adaptation to drought, but is probably selected in nutrient poor environments. This conclusion supports evidence provided by several authors …