The Colorado Desert District of California States Parks has had a long-term program to control tamarisk in critical resource areas, especially in riparian locations of Anza-Borrego Desert State Park. In 1995 a three year program to remove exotic plants in the District was funded by a private donor. The primary means of tamarisk removal is through the use of cutting by lopper or chainsaw with a follow-up of herbicide application using Garlon® 4 or Rodeo®. The basal bark method of Garlon® 4 application has been found very effective for specimens with a basal diameter less than four inches. This method precludes the need to cut the tamarisk, thereby saving tremendous amounts of labor. In areas of tamarisk monoculture such as along the shoreline of the Colorado River, the use of prescribed fire and mechanical removal by bulldozer has been employed.
In January of 1996 a twenty acre plot adjacent to the Colorado River was targeted for a prescribed burn at Picacho State Recreation Area (SRA). The north margin of the plot was the river, the east and south margins were campground roads, and the west margin was provided by a bulldozed fireline constructed at a width of 30-50 feet. This plot was deemed ready to bum since the tamarisk had entered dormancy and dead leaves covered both the tree branches and the ground. State Parks was assisted on this project by the Bureau of Land Management and the U. S. Fish and Wildlife Service, which each provided a fire boat to control the line in dense cane up and down river.
Ignition of the plot occurred at the down river margin, with prescription calling for a backing fire into the plot. Cane (Phragmites) ignited and fire spread rapidly with flame length reaching over thirty-five feet. The Phragmites consumed totally and moved the flame into the adjacent tamarisk where the fire quickly and surprisingly died out. Even though the tamarisk was laden with dead leave material, the stems and trunks appeared to be so water ladened that fire would not move into the thicket of tamarisk.
On a previous tamarisk prescribed burn a similar situation occurred, although the previous fire was in October when the tamarisk still held its leaves. In the October 1988 fire in Anza-Borrego Desert State Park, the unsuccessful burn was followed up with the chainsawing of about 20% of the standing tamarisk, then burned again in December of 1988 This strategy was successful, with the dead fuels on the ground building heat and carrying fire into the standing trees. The burned plot was then treated for stump-sprouting using Garlon 3A which we used before converting to Garlon 4.
The partially burned plot at Picacho SRA was bulldozed in its entirety with the massive amount of tamarisk biomass stacked into forty large piles, each approximately 30' x 30' x 15' high. These piles were allowed to dry for three weeks and were then burned in a two day period in March of 1996. A bulldozer was employed once again to turn the piles after each had burned to insure that all organic material was consumed by fire. The plot was then groomed to allow for efficient revegetation of cottonwoods, willows, mesquites, and palo verdes and the installation of an irrigation system.
A one month period brought tamarisk resprouts to the plot and a long-term retreatment program using Garlon® 4 has begun. The twenty acre plot has been divided into twenty-five quadrants to allow for a methodical treatment program and for analyzing varying treatment strategies.
If possible, use the lowest impact method of tamarisk removal. The sequence of treatments might follow this progression: 1) direct pulling of seedlings, 2) foliar spraying of seedling beds using Rodeo®, 3) cutting with loppers and spot application of Garlon® 4, 4) use of chainsaws followed by Garlon® 4, 5) basal bark treatment using Garlon® 4 mixed according to label, 6) prescribed burning followed by herbicide, 7) mechanical removal using heavy equipment followed by herbicide treatment of resprouts.
Burning can be effective for tamarisk biomass removal if performed at the proper time of year and herbicide treatment of resprouts is performed. Wildfires in tamarisk thickets should be viewed as an opportunity to begin a cutting/herbicide application treatment program. If prescribing a burn for tamarisk, consider entering the plot a month or two beforehand and cutting 20-25% of the largest trees down and allowing them to fall and dry. Work throughout the entire plot to equally scatter downed trees. This will provide ground fuels for the prescribed burn and preheating of the standing tamarisks, providing a higher likelihood of consumption. If the surrounding vegetation and terrain allow, plan for a head-fire rather than a backing fire, thereby gaining more heat which will bring a higher percentage of tamarisk consumption.
Burning always needs to be followed up with a methodical herbicide treatment program. Use of fire can be beneficial in almost total removal of biomass from the site, thereby allowing easier access to the stumps and root crowns for herbicide treatment. If fire removes less biomass than is necessary for access to the site, the use of heavy equipment can be employed if the site has been reviewed by qualified specialists for resource sensitivity.
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