Intra-specific variation in leaf attributes of four savanna tree species across a rainfall gradient in tropical Australia.

摘要

Leaf attributes of 4 savanna tree species (Eucalyptus tetrodonta, Erythrophleum chlorostachys, Buchanania obovata, Planchonia careya) were measured along a rainfall gradient (1650-950 mm per annum) in the Australian monsoon tropics. Leaves were collected from 3 physiological study sites, viz., Territory Wildlife Park (wet site), McDonald Airstrip (middle), and Cutta Cutta Caves Nature Park (dry site). As the mean annual rainfall decreased, leaf thickness increased for 3 (E. chlorostachys, E. tetrodonta, P. careya) of these 4 species. However, a corresponding decrease in leaf density for 2 species meant that leaf mass per area increased significantly only for one species. Physiological measurements were made during both the wet and dry seasons on comparable stands of vegetation near the extremes and middle of this gradient. Assimilation per unit mass was similar at all 3 sites but assimilation per leaf area was higher at the drier sites because leaves were thicker with higher mass per area. These results probably reflect reduced tree density and leaf area index at the drier sites, which offsets the lower rainfall, potentially allowing similar rates of assimilation per unit carbohydrate invested in leaves..