Greener Roadsides

Starthistle Reduced by Prescribed Burn

Reprinted excerpts from an article by Craig Thomsen, Program Manager for 65,000 acre Bear Creek Watershed Restoration Program and George Hartwell, Wildflower and Native Revegetation Coordinator, Office of Landscape Architecture, Caltrans

The Bear Creek Botanical Area is habitat for more than 100 species of native California plants and characterized as a microcosm of Bear Valley, one of the last remaining examples of Upland Wildflower Field in California. And the botanical area is ON HIGHWAY RIGHT OF WAY! It is one of twenty California plant community remnants discovered and protected by Caltrans. In the spring of 1998, it was first noted that yellow starthistle had invaded about one-third of the site. Within two years starthistle had spread over more than half the site in dense monocultures.

The site divides the roadway from a grazed rangeland area and has remained relatively unaffected by human activity for many years. Native grasses are abundant as are numerous wildflower species, some of which were extirpated from the adjacent lands by agricultural activity. Range Ecologist Thomsen used integrated efforts including mowing, string trimming, and hand pulling, beginning in 1999. The results were dramatic.

Carpets of wildflowers and native grasses blanket areas previously occupied by starthistle. Residual seed bank of starthistle, goat-grass and medusahead quickly responded to favorable conditions. It was therefore decided to burn in June. The burn objective was to prevent as much seed production as possible.

Craig Thomsen, UC Davis range ecologist, George Hartwell, and Scott Kuhn, Battalion chief of the California Department of Forestry and Fire Protection reviewed the plan.

A Caltrans truck safely leads traffic through the project area.

The burn begins with torch and water supply in hand.

Weed Management through an Interagency agreement between the Department of Forestry and Fire Protection and the Caltrans Office of State Landscape Architecture (OSLA) was the solution to this weed problem. Along with input from District 3 and the Colusa County Air Pollution control District, a "burn prescription" or plan was written. It was based on 3 criteria:

1. day's temperature must not exceed 90 degrees,
2. humidity must not fall below 20%, and
3. the wind must not exceed 12 mph.

the fire would not be ignited under those conditions, or if in progress, extinguished if any of the criteria were exceeded. In preparation for the burn, standing plants were mowed to help care the fire through the green starthistle.

Ignition was at 8:00 a.m. on June 28, 2000. By 10:30 a.m. air temperature reached 93 degrees, wind speed 5 mph, and humidity 44%. The fire was extinguished a few minutes later with 100% of the primary target area fully burned. After the burn, Thomsen eliminated surviving plants with a steel-bladed weed eater. He also sprayed the fenceline with roundup to reduce seed dispersal from the adjacent unburned BLM land. A safety note: a semi-tractor rig traveling adjacent the burn area at 25 mph will cause vortex wind disturbances, changing the behavior of the fire. Consequently, OSLA recommends traffic speeds during the burn operations be managed at less than 25 mph.

Results found no germinating star thistle. The only patch of medusahead in the burn area was destroyed. However, even if there was 100% kill and no seed production this year, more work will be needed in the future to deplete the existing seed bank in the soil.

Safety measures to personnel safety, traveler safety, and adjacent lands were important. The Department of Forestry provided three engine companies as well as an incident commander with supervisory staff. Each engine company carried a complement of at least three firefighters and resources (water, etc.) to contain any escapes. Aerial fire fighting resources were available and on alert.

Conclusions: OSLA concludes from evaluation of the prescribed fire process, it's planning and execution and the preliminary biological observations of this prescribed fire event, that it can be an effective vegetation management tool for Caltrans. However, the use of prescribed fire alone will result rarely in complete eradication of undesirable weed species, and should be implemented as one of the tools available in an overall, integrated strategy that incorporates multiple management techniques over time.