in the Pacific Northwest will be less vulnerable to drought and fire over the
next three decades than those in the Rocky Mountains and Sierra Nevada,
computer modeling by researchers in Oregon State University’s College of
findings, published Global Change Biology, represent an important tool for
scientists and land managers because woodlands throughout the western United
States are under increasing stress from accelerated rates of drought-related
mortality related to global, human-caused climate change.
the Northwest’s hemlock, Douglas-fir and redwood forests have tremendous
potential to counteract climate change via their carbon-sequestration
abilities, meaning policies that promote stewardship of those forests is
critical, the scientists say.
prolonged droughts and catastrophic wildfires in the West have raised concerns
about forest mortality and how that might impact forest structure and ecosystem
services and also the economic vitality of nearby communities,” said
corresponding author Polly Buotte of OSU’s Department of Forest Ecosystems and
Society. “Forests in the West support high species diversity and some Pacific
Northwest forests are among the highest carbon-density forests on Earth.”
and College of Forestry colleague Beverly Law led a collaboration that modeled
13 different major forest types from around the western United States, taking into
account climate conditions and atmospheric carbon dioxide levels over the next
model was high-resolution both from a spatial standpoint – it broke forests
into grids of 16 square kilometers – and also because it looked at
species-specific responses to environmental variables.
model calculated multiple biophysical and biogeochemical processes, including
surface heat fluxes, photosynthesis, evaporation, transpiration, carbon
allocation to plant tissue, decomposition and nitrogen cycling,” Buotte said.
researchers, who also included David Rupp of OSU’s College of Earth, Ocean and
Atmospheric Sciences, developed metrics of vulnerability to short-term extreme
and prolonged drought.
show that water-limited forests in the Rockies, the
Southwest and the Great Basin will be the most vulnerable to future drought-related mortality,” Buotte said. “We expect vulnerability to
future fires will be highest in the Sierra Nevada and portions of the Rocky
Mountains. Forests along the Pacific coast and western Cascades regions, where
there is ample rain, are projected to be the least vulnerable to either drought
from drought causes trees to shed leaves, limiting their capacity for
photosynthesis; insect infestations also make life hard for drought-affected
analyses indicate strong potential for continued levels of drought-related forest mortality in the southern Rockies and in the
Southwest in the coming decades as those forests are likely to suffer from a
changing climate,” Buotte said.
researchers stress that there is a lot of spatial variability in future
vulnerability and that fire vulnerability is not the same as fire intensity.
do not imply that areas labeled highly vulnerable will burn or that if ignited
they will burn with high intensity, but they are at greater risk in the coming
years than they have been historically,” Buotte said.
U.S. departments of Agriculture and Energy supported this research.