Diversity is strength, even among forests. In a paper published in Nature, researchers led by University of Utah biologist William Anderegg report that forests with trees that employ a high diversity of traits related to water use suffer less of an impact from drought. The results, which expand on previous work that looked at individual tree species’ resilience based on hydraulic traits, lead to new research directions on forest resilience and inform forest managers working to rebuild forests after logging or wildfire. Surprisingly, says Anderegg, a forest’s hydraulic diversity is the predominant predictor of how well it can handle a drought. “We expected that hydraulic traits should matter,” he says, “but we were surprised that other traits that a lot of the scientific community have focused on weren’t very explanatory or predictive at all.” Hydraulic traits are connected to the way a tree moves water throughout the organism – and how much drought stress they can take before that system starts breaking down. But droughts, when they strike, don’t go after individual trees – they affect entire ecosystems. Anderegg and his colleagues, including collaborators from Stanford University, Princeton University and the University of California, Davis, compiled data from 40 forest sites around the world. The sites are equipped with instruments called flux towers that measure the flows of carbon, water and energy from a forest. They’re also equipped with environmental sensors, including soil moisture sensors, to produce a picture of how much water is moving into and out of the site. Forests with a greater diversity of hydraulic traits in its tree species showed less of a dip in forest function (measured by fluxes of water and energy and soil moisture) than less-diverse forests.
From University of Utah Photo John Vlahakis