|Publication Type||Journal Article|
|Year of Publication||2010|
|Authors||Orchard, KA, Cernusak, LA, Assoc Prof Hutley, LB|
|Journal||Functional Plant Biology|
Islands of monsoon rainforest and Melaleuca swamp punctuate vast tracts of savanna in monsoonal northern Australia. Seedlings of species from each of these habitat associations were grown in a common garden. Monsoon forest species had higher specific leaf area, lower photosynthetic capacity and lower photosynthetic light compensation points, and required lower irradiance to achieve 50% of light-saturated photosynthesis compared with savanna or swamp species. These traits probably contribute towards greater shade tolerance beneath dense monsoon-forest canopies, whereas savanna and swamp canopies are relatively open. Swamp species, especially two Melaleuca species, had high stomatal conductance and small CO2 drawdown during photosynthesis, and more negative leaf delta C-13, compared with monsoon forest and savanna species. Higher stomatal conductance increases carbon uptake during photosynthesis and a high transpiration rate would increase transport of nutrients to absorbing surfaces in the root by mass flow. Thus, a strategy of high transpiration and low water-use efficiency appears to be favoured in swamp species compared with monsoon-forest and savanna species. Instantaneous measurements of the ratio of intercellular to ambient CO2 concentrations (c(i)/c(a)) explained 81% of variation in leaf delta C-13 across 44 species sampled in this and other studies, suggesting that leaf delta C-13 generally provides a robust proxy for comparisons of c(i)/c(a), even when applied across species.