Invasive weeds thrive in wake of fires, contribute to further disasters
By MITCH LIES
BURNS, Ore. -- The Long Draw Fire, which charred 557,441 acres in southeastern Oregon in July, is the state's biggest fire in more than a century, "but it won't end up being the biggest," Agricultural Research Service scientist Roger Sheley said.
Sheley, lead scientist for invasive plant ecology for the USDA research center in Burns, said an influx of non-native annual grasses such as cheatgrass and medusahead into Eastern Oregon is increasing the likelihood of more and bigger fires.
"Cheatgrass and medusahead love fires, and fires love them," Sheley said, "and cheatgrass and medusahead are spreading."
Cheatgrass goes dormant earlier than native grasses, creating earlier and longer fire hazards than native perennial bunchgrasses, he said.
Also, cheatgrass and medusahead tend to bunch together in a manner that creates a continual fuel source. Native bunchgrasses grow in clumps several feet apart.
"It takes a fair amount of wind to get a flame that will carry across those bunchgrasses," Tony Svejcar, research leader at the center, said.
USDA scientists at the Burns-based research center said that slowing a cycle that in recent years has resulted in more and bigger fires may require replacing thousands of acres of cheatgrass and medusahead with native perennial bunchgrasses.
Changing the mix will be difficult, however, given that cheatgrass and medusahead typically outcompete native bunchgrasses after fire strips a landscape of vegetation.
"Until you get out of that fire cycle, there is no real opportunity to restore those sites," Svejcar said. "You have to get the cheatgrass out of there, and get out of that frequent burning cycle.
"These annuals are just so good at occupying a site, at putting down roots quickly," Svejcar said. "These things are adapted to regrowing every year from seed."
Fire conditions in Eastern Oregon were ideal this summer, scientists said, as hot, dry weather and windy conditions combined with a heavy fuel source to sweep fires started by lightning rapidly across vast landscapes.
The Long Draw Fire spread more than 200,000 acres in one day. The Miller Homestead Fire, which burned 160,800 acres just west of the Long Draw Fire, ran 100,000 acres in one day, according to reports.
The Miller Homestead Fire is the 11th biggest fire in Oregon in the last 162 years, according to the state Department of Forestry. The Long Draw Fire is the third biggest, and the biggest in 147 years.
Scientist said heavy spring rains in 2011 also contributed to the breadth and speed of the fires' spread. The rains contributed to lush stands of native grasses that weren't grazed down to crowns last summer. And a lack of snow this winter left the ungrazed dormant native grasses standing tall, fueling the fires' movement.
As ranchers and federal land managers consider how to restore the charred rangeland, several questions are at play, including whether to seed acreage or let plants come back on their own.
"Under most conditions, we think these bunchgrasses survive a fire," Svejcar said.
Also, land managers will consider whether to replace lost sage grouse habitat by broadcasting seed, planting seedlings or leaving areas to recover on their own.
The two fires destroyed about 8 percent of the state's prime sage grouse habitat, said Kirk Davies, a rangeland scientist with ARS in Burns.
Left on its own, sagebrush typically will return to an area, Davies said, but it can take many years.
"Especially when you have a huge fire, with no islands of sagebrush to disperse seed, it can take a long time for sagebrush to come back on its own," Davies said, "which wouldn't be a big deal if sage grouse wasn't already a candidate species (for listing under the Endangered Species Act)."
BLM officials typically require a two-year wait before allowing cattle back on burned allotments.
Waiting two years in this case could be devastating for some, ranchers said.