Seasonal impacts on leaf attributes of several tree species growing in three diverse ecosystems of south-eastern Australia

Abstract

Patterns of leaf attributes were examined for six woody species growing in a eucalypt woodland, a mangrove, or a heathland in coastal New South Wales, Australia, during winter and summer. It was found that the rate of assimilation per unit leaf dry mass (A_mass) of the mangrove species was largest, woodland species exhibiting an intermediate rate and heathland species the smallest values of A_mass. Mean habitat A_mass did not change from winter to summer in the woodland or mangrove species but increased significantly in the heathland species. Average specific leaf area (SLA) was largest for the mangrove species and smallest for the heathland species, with woodland species showing intermediate values. SLA of all species within a habitat did not change from winter to summer. Mean foliar nitrogen (N_mass) of the mangrove species was highest, intermediate for woodland species and lowest for heathland species. N_mass was significantly related to A_mass in both summer and winter and the individual slopes for this relationship in the summer and winter differed. In contrast, a common slope was fitted to the relationship between SLA and A_mass for the two seasons. A common slope between seasons was also shown for the relationship between SLA and N_mass. There was no significant difference in slope elevation between summer and winter for the SLA v. N_mass relationship. Trends within relationships among leaf attributes were the same as those found for a wide range of plant species worldwide, but the absolute values were lower than those found elsewhere. Therefore, the 'global relationships' in terms of trends (positive or negative) that have been determined overseas apply in Australia but the elevation of the slope and the magnitude of the slope are reduced (A_mass v. N_mass) or increased (A_mass v. SLA and N_mass v. SLA) compared with global trends.