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You are here >1Up Info > Wildlife, Animals, and Plants > Plant Species > Shrub > Species: Toxicodendron diversilobum | Poison-Oak

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SPECIES: Toxicodendron diversilobum | Poison-Oak
IMMEDIATE FIRE EFFECT ON PLANT : Fire top-kills poison-oak [13,16]. Wirtz [68] reported that an October, 1953, wildfire in a coastal sage scrub/grassland community near Berkeley, California, top-killed all poison-oak present, leaving only large branches and stumps. Rhizomes on the soil surface are probably killed by all but light-severity fire, and shallowly buried rhizomes are probably killed by moderate to severe fire. More deeply buried rhizomes are probably not killed. DISCUSSION AND QUALIFICATION OF FIRE EFFECT : NO-ENTRY PLANT RESPONSE TO FIRE : Poison-oak sprouts vigorously from the root crown and/or rhizomes after fire [13,15,43,46,52]. It sprouts in the first postfire growing season, and for several years thereafter [13,16,52]. Poison-oak sprouts were noted the September following the July, 1985, Wheeler Fire on the Los Padres National Forest, California. The wildfire had spread into a riparian zone containing poison-oak; prefire poison-oak density was unknown. By postfire year 3, poison-oak sprouts dominated most burn plots in the riparian zone [18]. Westman and others [67] estimated that poison-oak fails to sprout when fire reaction intensity exceeds 200 kcal/sec/sq m. Their estimate was derived by modelling fire behavior of a backfire set in coastal sage scrub in the Santa Monica Mountains of California, and observing sprouting the following year. The coastal sage scrub had not burned for 20 to 22 years. Poison-oak also establishes from seed after fire, although this response is not well documented in the literature. Poison-oak seedlings were osberved following site preparation and prescribed burning of an interior live oak-blue oak woodland in Madera County, California. Prefire poison-oak seedling density was 0 percent; seedling density at postfire year 1 was 42 per 8,712 square feet [20]. DISCUSSION AND QUALIFICATION OF PLANT RESPONSE : Fire response is probably related to Poison oak's successional role in the plant community. Dense poison-oak thickets may develop in chaparral that is control burned several times [12]. Poison-oak may become locally extinct in Douglas-fir forest, however, that is burned every 4 years for 20 years or more [53]. FIRE MANAGEMENT CONSIDERATIONS : Urushiol volatilizes when burned, and human exposure to poison-oak smoke is extremely hazardous [40]. The smoke often poisons people who think they are immune to the plant [46]. Poison-oak vines are a ladder fuel [61]. Goats can be used as an alternative to precribed fire for fire hazard reduction at urban-wildland interfaces. Near Oakland, California, goats were put on a Monterey pine-redgum (Eucalyptus camaldensis) forest with a heavy shrub understory and on an adjacent site where the forest was managed as a fuelbreak and had less shrub cover in the understory. Goat utilization of poison-oak was in the fuelbreak 67 percent, somewhat lower than utilization of toyon, California blackberry, and coyotebrush. Annual production of poison-oak biomass before goat browsing in the fuelbreak was 99 kilograms per hectare; it was 33 kilograms per hactare afterwards. Total biomass of forage species was significantly (p<0.05) reduced [61]. A stocking rate of 600 goats per hectare on the Oakland site broke the vertical live fuel continuity in the dense shrub stand. Initial goat browsing to reduce biomass and vertical fuel continuity could be followed up by prescribed fire [61].

Related categories for Species: Toxicodendron diversilobum | Poison-Oak

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Information Courtesy: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory. Fire Effects Information System

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