Associate Professor Susan Laurance from James Cook University is running a large-scale drought project in the Daintree rainforest section of the Wet Tropics region. After more than two years of preparation, construction of the rainforest field laboratory has recently been completed. Her team of researchers aim to determine which rainforest trees are more successful at surviving drought and which are vulnerable to prolonged water stress.
Drought is a natural feature of climate; however the frequency of severe droughts is increasing as a result of climate change. Droughts alter the composition, structure and function of forests. Of particular concern are potential increases in tree mortality associated with physiological stress.
The research team have established their experiment at the Daintree Rainforest Observatory. They have constructed an experimental structure consisting of over 3,000 clear plastic panels designed to create an understorey ‘raincoat for a rainforest’. The panels divert rainfall to a system of gutters and channels which will remove 40% of rainfall from the site to create an artificial mega-drought.
Prior to constructing the experimental drought structure, the researchers spent two years monitoring the growth and survival rate of 700 trees and 1,000 lianas (woody climbing vines) in a 1-hectare plot below a 47-meter-tall canopy crane.
Among their key goals is determining whether big trees are especially vulnerable to droughts, as suggested by recent research. If this is found to be the case it could have profound implications – because big trees not only store enormous amounts of carbon and provide food and shelter for a huge number of vertebrate, invertebrate and epiphytic species, but they also dictate the structure, dynamics and function of forests.
There’s ample evidence that future droughts will be worse than what we’ve already experienced, making it very important we develop a better understanding of how droughts will affect rainforests and what might be feasible ways to reduce their impact.