Some people believe more is always better. And while sometimes that might be true, a Waterloo scientist has shown that with trees, it's more about planting the right trees instead of mass planting more trees.
In a recent study, Dr. Julie Messier, a biology professor in the Faculty of Science, Sabina Henry (MSc student), and their collaborators set out to decipher the traits that make some trees grow better than others in warmer and drier climates. Their findings could play a role in future-proofing our Canadian forests against climate change by planting trees with the right traits.
Messier's team studied black spruce trees, and results showed that a combination of three traits made that species grow well in warmer and drier climates, but all three had to be present to make a difference. The traits are that the trees have to have few needles, be conservative for water use, and be conservative for carbon use.
"The most surprising part of this study is that individual traits weren't sufficient for the trees to be successful in that climate," says Messier. "For example, we thought that conservative water use would be a determining factor on its own, but that alone did not make the trees grow well in those conditions."
The team had their predictions about which traits would be most important, expecting that efficient water use and efficient leaf cooling would make trees grow better, but what the researchers found was unexpected. Data showed that needles with conservative carbon use supported better growth under warmer and drier conditions, although carbon use does not directly reduce heat and water stress. The research suggests that efficient carbon use is under selection indirectly, because needles can either be conservative for all resources or acquisitive with all resources.
"We were not expecting fewer needles to be one of the traits under selection because having fewer needles also comes at the cost of doing less photosynthesis," says Messier. "We think this trait helps because trees with fewer needles lose less water through transpiration. The trees doing best are using a double safety strategy: they have fewer needles to lose water, and each of these needles loses less water."
Knowing that these three factors can play a large role in how well a species can cope with warming temperatures is a valuable tool for those planning the future of Canadian forests. This study will give practitioners the information they need to choose the right trees to plant under a warming climate, ensuring that our Canadian forests can stand the test of time and climate change.
The paper, "Selection for fewer, water- and carbon-conservative needles in black spruce trees under warm, dry climates," was recently published in Annals of Botany.
