Shrub die-back contributes to fire danger

Throughout Central Oregon - visible from many trails and roads - are large swaths of brown and dead-looking native shrubbery. The unsightly die-off, while not entirely unexpected, is much worse this year than at any time in recent memory.

Last winter's extremely cold temperatures were unusual for our area, and some of the region's native plants suffered as a result. Most notably, the region's Ceanothus, or snowbrush, really took a beating. Also affected, although to a lesser extent, the manzanita suffered from the unusual cold snap.

In terms of plant hardiness, the U.S. Department of Agriculture lists both Ceanothus and manzanita as Zone 5 plants. The problem is that Zone 5 temperature tolerance for these plants reaches down to only about -20 degrees Fahrenheit. Last December, temperatures in the surrounding areas were recorded in the -22 to -26 degree range.

This phenomenon of shrub die-off has been noted in South Central Oregon, as well. Clint Albertson, interagency fire planner for the Fremont-Winema National Forests, said that a "very rough guesstimate" is that, in a typical year, Ceanothus may normally suffer 5 to 25 percent frost damage with "little or no plant mortality." However, "This year," he said, "a broad probable range is 50 percent to 90 percent frost damage with 5 to 25 percent plant mortality...."

In terms of fire danger, Albertson noted, "Frost damage has added dead fuels to the surface and canopy, whether the plant itself is live or dead." In other words, even though many of the plants may still be alive, their dead, brown leaves will add significantly to the fire potential.

Forest ecologist for the Sisters Ranger District, Maret Pajutee, made a similar assessment about the potential fire hazard.

"It's a lot of fuel, and it's not going to help things," she said. She noted that the manzanita, in particular, is highly flammable under normal circumstances and has "lots of oils."

Brian Tandy, forest products program manager for the Deschutes-Ochoco National Forests, said, "I've noticed varying amounts of the Ceanothus die-back, but this is the worst I've seen in the 20 years that I've been in this area. It has a lot to do with the snow pack. We didn't have much snow cover when the really cold temperatures hit, so it was exposed."

He further explained that deeper snow helps to protect the plants by providing insulation against the extreme cold, such as that experienced this past winter. Tandy noted that, in some areas where the snow was deeper, the bottom part of the plants did just fine, while the upper parts that were protruding from the snow suffered frost damage. This condition was more often seen at higher elevations that experienced more early snow.

Tandy, who is a professional silviculturist, observed, "This die-back has left a lot of dead leaves, so I think all that dead plant matter will carry a fire better and will elevate the fire hazard."

Early signs indicate that Tandy's prediction is accurate. According to Albertson, "Fire behavior observations on April and May prescribed fires from several Klamath and Lake County locations report that the Ceanothus burned readily and vigorously when normally it is difficult to carry fire."

Ceanothus is known for the fragrance of its evergreen leaves and often grows to several feet in height. The plant prefers sunlight and thrives in open areas with good drainage. As a result, it is commonly quick to colonize burned-over areas in the wake of forest fires.

Manzanita also has evergreen leaves, but is distinguished by the orange-red bark on its stems. The name "manzanita" is derived from the Spanish word for "little apple," which is a reference to the appearance of the small fruit borne by this plant.

In reference to this year's unusual plant die-off, Tandy said, "It's going to be really interesting to watch it and see how much of it bounces back."

As for now, no one seems to know for sure to what extent the plants will recover; but, in the meantime, it appears that the added fuel load of the widespread dead leaves will only exacerbate what looks to be a very dry and dangerous fire season for 2014.