OSU to study forest mortality

Oregon State University has received a five-year, $4 million grant from the United States Department of Agriculture to investigate increasing impacts of drought, insect attacks and fires on forests in the western U.S., and to project how the influence of climate change may affect forest die-offs in the future.

The researchers will also enhance an earth system model to allow them to predict when forests are becoming vulnerable to physiological stress and then create strategies to minimize impacts of climate, insects and fire.

“The western United States has gone through two decades of devastating forest loss and we don’t even fully know why it happened, much less how to predict these events,” said Philip Mote, director of the Oregon Climate Change Research Institute at OSU and a principal investigator on the grant. “Certainly wildfire, bark beetle infestation and drought play a role, but the intersection of these factors with forest management decisions hasn’t been well-explored.

“A change in severity of drought, for example, can make the difference between trees losing some needles and wiping out the entire stand,” added Mote, a professor in the College of Earth, Ocean, and Atmospheric Sciences at OSU. “The margin between life and death in the forest can be rather small.”

“Climate variation and extremes can impact trees differently depending on species-specific traits that determine how they compete and respond to environmental conditions,” Beverly Law, a professor in the Department of Forest Ecosystems and Society, said. “We know little about how physiological limits vary by species, and have not incorporated such knowledge in earth system models.”

The OSU researchers note that forest management decisions could potentially play a role during periods of drought, for example. Drought-stressed trees become vulnerable when they experience vapor pressure deficits – and cannot take in enough water to sustain them, or to remain vigorous enough to help repel invading bark beetles, said Law, who is co-lead principal investigator on the project.

An excess of trees in an area of limited water might benefit from targeted thinning so fewer trees remain to compete for the same amount of water, Law noted. However, forests that already have low densities “are not expected to respond well,” she said.

“What we don’t know,” Mote said, “is what the threshold is between stress and mortality, which trees to thin and how many, and whether such a strategy not only works, but is economically feasible for landowners.”

Law said the intervention strategies “should not result in potentially harmful ecological impacts on habitat and soil quality.”

As part of the study, the researchers will run computer models that will utilize a crowd-sourced computing effort called Weatherathome.net, through which a network of thousands of volunteers will use their home computers to run climate model scenarios. Such a network can equal or exceed the output of a supercomputer.

The OSU grant is part of the inter-agency Decadal and Regional Climate Prediction Using Earth System Models Program, which is coordinated by the National Science Foundation and includes USDA and the Department of Energy.

Image above: Photo Courtesy OSU. The defoliation from major epidemics of bark beetle infestation, such as these in stands of lodgepole pine, reflects the challenges tree species across much of the West face as climate changes and threatens their future ability to survive.