Climatic control of structure and phenology of foliage shoots in dicotyledonous overstorey and understorey strata of subtropical plant communities in southeast Queensland

Leaf Area and Internode Length of foliage shoots of dicotyledonous overstorey species become greater in magnitude as soils of plant communities decrease in nutrients. The overstorey of heathy open-forests and heathlands grows during summer to produce large leaves with long internodes, whereas the overstoreys of the savanna and rainforest edaphic complexes grow during spring and autumn. With decreased solar radiation (transmitted through the gaps in the overstorey canopy), reduced development in Leaf Areas has been observed in nutrient-rich ecosystems; little change in Leaf Specific Area and Internode Length (except in the cool-temperature Nothofagus forest) of dicotyledonous foliage shoots of the understorey stratum has occurred at the same time. Understorey plants in nutrient-poor ecosystems produce small leaves with very short internodes. Compaction of leaves on foliage shoots in nutrient-poor ecosystems results in increased temperatures at the stem-air interface, as foliage shoots are exposed to direct solar radiation under still-air conditions. Increased temperatures at the stem-air interface of understorey foliage shoots, with small, densely-packed leaves, induce earlier seasonal shoot growth and flowering in the understorey stratum. These foliage attributes appear to be an evolutionary response that optimises photosynthesis in plant communities growing on nutrient-poor soils. -Authors