Invasive weeds establish greater foothold on range


Issue Date: April 26, 2017
By Ching Lee
Sheep and goats belonging to Merced County rancher Andrée Soares graze a field in residential Half Moon Bay as part of the city’s routine vegetation management. Soares says her contracted grazing business has gotten record calls this year due to increased weed growth.
Photo/Paolo Vescia
Sheep and goats belonging to Merced County rancher Andrée Soares graze a field in residential Half Moon Bay as part of the city’s routine vegetation management. Soares says her contracted grazing business has gotten record calls this year due to increased weed growth.
Photo/Paolo Vescia

The state's forests and wildlands may look green and lush now, but don't expect firefighters and land managers to be resting on their laurels.

Vegetation growth has exploded with this year's record rainfall, especially invasive weeds that tend to die and dry out quickly, creating more fuel for wildfires and turning the state's landscapes into tinderboxes.

"It probably is going to be one of those potentially big fire seasons, just because there is so much annual forage out there," said Scott Oneto, a University of California farm advisor for the Central Sierra Cooperative Extension, which covers Amador, Calaveras, El Dorado and Tuolumne counties.

Expect to see more weeds this year, Oneto said, especially late-season annuals such as yellow starthistle, medusahead, goatgrass and stinkwort. The latter two have expanded at a "tremendously fast rate," he said. These plants establish deep roots and take advantage of the soil's high moisture from April to June.

Oneto said he's also seeing lots of brush and regrowth in areas that previously burned, including in Amador and Calaveras counties where the Butte Fire occurred, and in El Dorado County, the site of the King Fire. Shrubs tend to resprout after fire disturbances, with much of the growth coming in the next two months, he added.

"Unfortunately, they're kind of growing at a rate that we can't keep up with in terms of management, so there's a lot of fuel added back into that landscape very quickly," Oneto said.

The state's massive tree die-offs stack another layer of fuel to forests, creating threat for catastrophic wildfires, he said. The U.S. Forest Service has estimated that more than 102 million trees have been killed since 2010 due to stresses created by drought.

Cal Fire spokesman Scott McLean said the department continues to work with federal, local and utility partners to remove dead and dying trees that pose the greatest risk to public safety.

In the last two years, the agency has increased its staff of firefighters, which have been kept busy doing fuel reduction on a minimum of 35,000 acres that Cal Fire plans to treat this year. The projects include mowing, creating fire breaks and doing prescribed burns to remove invasive grasses and brush. In addition, the department will be doing 250,000 defensible-space inspections this year.

"We don't just fight fire," McLean said. "We're also heavily involved in the prevention aspect, whether it be a structure fire or wildfire."

The repercussions of the state's multi-year drought are "not going to go away in one winter," he added, and despite the heavy rain year, the southern part of the state has already started to dry out.

The biggest difference the wet year has made is possibly delaying the fire season by keeping soils, shrubs and trees moist longer, said Bill Stewart, a forest management specialist at UC Berkeley. He noted that coastal Oregon has just as much fuel as California, but the region is not prone to fires because it stays wet most of the time. With current conditions, he said it may be June or July before the state's landscapes dry out, as opposed to May during drought years.

"My prediction is we're going to have a shorter fire season in the front end," he said. "How long it goes is always a different issue. If we have a long, dry fall, we could have fires in October, November. We've had fires after Christmas because that's when it finally dries."

Travis Bean, a UC weed science specialist in Riverside, said invasive plants in his region are "already really crispy" and he expects it will be "a pretty scary year for fire" due to the huge amount of fuel lying on the ground. He noted that mustards in the southeastern part of the state have had "an extremely successful year" and have put out "an incredible amount of biomass."

Because many of the state's invasive plants tend to be cool-season annuals, Bean said management to control their spread needs to happen in the early spring and fall—before the plants get a chance to produce viable seed. He noted that in the South State, invasive grasses such as medusahead and barb goatgrass—two big fire contributors—start going to seed in March and early April. Once that happens, efforts to kill the plants are a wasted effort, he said.

"They die anyway, whether you kill them or not," Bean said. "They rely every year on a residual seed bank to get going. The way you manage the seed bank is you don't let the plant set seed."

Years of drought have dwindled those seed banks, making this year ideal for knocking down annual weed populations and encouraging desirable native plants to regenerate, he said.

To do an effective job, treatment—whether by livestock grazing, herbicide or controlled burning—should be scheduled before the plants drop their seed. Doing a burn after seeds have fallen could allow invasives to thrive, as the fire destroys everything but viable weed seeds remain on the ground, coming back to dominate the landscape next year.

Bean lamented that for much of the state, the window of opportunity may be closed to do the kind of weed management he described, as many of the annual weed species have already gone to seed.

But for Northern California, Oneto said it's not too late. He noted most weeds are just getting established and there's still a month or two before they flower and set seed, "so there's plenty of time for people to act."

Merced County rancher Andrée Soares, who runs a commercial sheep and goat business that specializes in contracted grazing, said she has gotten "a record number of calls" this year from municipalities, agencies and landowners seeking her services.

She noted that fire agencies have become more stringent about overgrown weeds and are putting requirements and deadlines on landowners to take care of the problem. Municipalities and agencies responsible for keeping creeks clear have herbicide restrictions in those areas and are increasingly turning to livestock to control vegetation.

With the amount of weed growth out there this year, Soares said her animals are going in early and taking much longer to do the job. Some agencies are now having her come in twice a year—in the spring and fall—to do cleanup.

"People are more concerned about fire," she said. "I think it's because of the fire experience we've had in California over the past five years and knowing what's leading to that. Land managers are being proactive and getting in contact with us earlier, trying to plan ahead, which is great."

(Ching Lee is an assistant editor of Ag Alert. She may be contacted at clee@cfbf.com.)

Permission for use is granted, however, credit must be made to the California Farm Bureau Federation when reprinting this item.