The water trading strategies of plants
Plants trade water for carbon – every litre of water that they extract from the soil allows them to take up a few more grams of carbon from the atmosphere to use in growth. A new global study, led by Australian researchers and published this week in Nature Climate Change, shows that plants trade their water wisely, with different plant species having different trading strategies depending on how much it costs them to obtain their water.
"Our study looks at how much extra water it would take for a plant to gain one more gram of carbon", says Dr Yan-Shih Lin of Macquarie University, lead author of the study.
"We predicted that individual plants should keep this exchange rate constant, but that the exchange rate should differ depending on what type of plant it is and where it grows".
Comparing data from the different ecosystems showed that most of the researchers' predictions were supported, indicating that plants have adapted their water-use strategies to their environments. The biggest surprise was that evergreen savanna trees were among the most spendthrift plants with water, despite living in hot and arid environments.
The researchers expected that plants with costly water transport structures, such as conifers and trees with dense stemwood, would be more conservative with their water, while grassy plants should be more spendthrift. They also predicted that plants growing in cold or dry environments should be more miserly with their water than plants adapted to hot or wet environments.
"We crowd-sourced the data we needed to test these predictions", says Professor Belinda Medlyn, of the University of Western Sydney.
"We couldn't travel the whole world ourselves, so we contacted other researchers around the globe and together we put together data from all kinds of ecosystems, from Arctic tundra to the Amazon rainforest to the backblocks of Australia."
"This work is important because it provides insights into how plants have adapted to their environments" says Dr Lin.
"Vegetation plays a really major role in the Earth system, by storing carbon, moving water around the landscape and cooling the planet's surface. These results provide us with crucial new information needed to predict these effects, especially under different climate-change scenarios."