Leaf Level Physiology, Chemistry and Structural Traits, Far North Queensland Rainforest SuperSite, Daintree, 2012

Objectives: (1). Quantify rates of leaf respiration (both in darkness and in the light) and associated leaf traits in a wide range of tropical tree species (2) Establish the extent to which rates of leaf respiration and associated traits change in response to changes in light availability within the canopy. (3). Quantify the temperature dependence of leaf respiration of tropical tree species, using leaves sampled from the top and lower positions of the canopy. Experimental design and methods: In September 2010, we surveyed rates of light-saturated photosynthesis (measured at ambient and elevated atmospheric CO2 concentrations), leaf respiratory CO2 release (both in darkness and in the light) and related leaf traits (area:mass ratios, and concentrations of nitrogen, phosphorus and soluble/insoluble carbohydrates) in 16 tropical species growing at the Cape Tribulation Canopy Crane site. Leaves were sampled at two positions in the canopy (sun-exposed/top-canopy and shade-leaves/lower canopy). Light response curves of leaf CO2 exchange were used to calculate rates of leaf respiration in the light (using the ‘Kok’ method). We will also quantified short-term temperature dependences of leaf respiration in the upper and lower canopy leaves.