Dry winters and long periods of drought, combined with fire suppression, are affecting the health of Central Oregon trees, particularly the junipers of the High Desert, according to an Oregon State University forester.
Nicole Strong, a forestry and natural resources extension agent for OSU, described an increased amount of tree mortality — including junipers — in Deschutes, Crook and Jefferson counties.
Junipers on the High Desert have become more fragile in recent decades, thanks to fire suppression policy, Strong said. Periodic fires thin forests and improve the health of existing trees. When fires do not occur, forest density increases, resulting in more competition for water and space to grow.
“This is the main reason we see a lack of resilience and mortality during periods of drought, as well as when there are insect or disease outbreaks,” she said. “If nothing is done, such as prescribed burns, this will be compounded in the future according to climate change models.”
The tree deaths have also been noticed by the Bureau of Land Management, which manages thousands of acres of juniper woodlands in Central Oregon. Deschutes Field Manager Jeff Kitchens described dying junipers in the High Desert between the Bend Airport and Powell Butte, as well as Crooked River Ranch.
“I am getting calls from landowners regarding trees on adjacent public lands and we wish we could provide an answer. People are noticing the dying trees and we are directing them to reach out to local extension offices,” Kitchens said.
BLM does occasional juniper thinning projects designed to restore range conditions and improve water availability.
“Our agency has treated thousands of acres in the last decade to remove juniper for fuels reduction,” said Kitchens. “We will continue to implement these treatments moving forward, where and when feasible.”
Juniper trees typically grow between an elevation of 2,600 and 9,800 feet and can live up to 1,600 years. Their berry-like cones, 5-10 millimeters in diameter, are an important source of food for birds native to Central Oregon, including Clark’s nutcracker and the American robin. Native Americans used the berries for medicinal purposes.
Juniper woodlands started to expand after settlers moved west, possibly due to overgrazing by cattle, which ate through the high desert grasses that historically contributed to wildfires.
Today there are even fewer threats to the junipers thanks to fire suppression efforts, such as fire retardant spread by planes and aerial water drops, that prevent a wildfire from burning too many acres.
“Historically, juniper were often restricted to rocky outcroppings and other areas not prone to burning from wildland fires,” Kitchens said. “Fire suppression and other human activities have allowed juniper to spread throughout the region.”
The BLM has no imminent plans to remove dead trees.
“If at any time areas affected were to directly be safety hazards to human life and or property we would work with our partners and neighbors to prioritize treatments. Some mortality, which may be a natural process of thinning and forest/woodland succession, will most likely benefit the ecosystem and require little, if any, active management from us,” Kitchens said.
Toni Stephan, Horticulture and Small Farms instructor at OSU Extension, said the juniper deaths in the region are merely part of a natural cycle that occurs every couple of decades due to periodic drought combined with an overpopulation of trees.
“Is this going to kill off all the juniper? No. We have junipers in various stages of life,” Stephan said. “Some trees have naturally better stress management and they beat out the weaker ones.”
Stressed trees can send off signals to insects that they are dying and ready to be finished off. The result is that many of these trees may be under attack by beetles, she added.
In spring, a juniper tree can use around 20 gallons of water per day. In midsummer, if water is available, a juniper can transpire 30 to 40 gallons of water per day.
“Junipers suck up a lot of water, and the more there are in one area, the better chance that some will lose — it’s survival of the fittest,” said Stephan.