Item 3: PH on Ordinance Prescribed Wetland Management Burning

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USE OF PRESCRIBED FIRE IN WILLAMETTE V ALLEY NA TIVE PRAIRIES Edward R. Alverson The Nature Conservancy non-native plants. Experience with prescribed burning in native prairies began in the 1970's at Finley National Wildlife Refuge, and continued in the 1980's on land at Fern Ridge Reservoir owned by the US Army Corps of Engineers, and at The Nature Conservancy's Willow Creek Natural Area. Eight prescribed bums have been conducted at Willow Creek, in 1986, 1987, 1991, 1994, 1996, 1998,2001, and 2005. Additional prescribed bums have occurred on BLM lands in west Eugene during the 1990's and 2000's. In general, the results ofthe bums have supported the hypotheses listed above. Typically, new green growth begins to sprout within two weeks after the bum; species such as tufted hairgrass, the dominant native grass in wet prairies, grow more vigorously through the fall and winter than in unburned areas. The following year, and often the following two years, see increases in the flowering and seed production of many native prairie plants. With increased flowering and seed production, the fire adapted species may gradually increase in population size. For example, a study ofthe State and Federal listed endangered Bradshaw's lomatium (Lomatium bradshawii) found that within two years of a fire the populations showed an increase in density of vegetative and reproductive plants (Pendergrass et aI., 1999). At Willow Creek, monitoring data consistently show native species that were used as food plants by Kalapuya people such as camas (Camassia quamash), wild onion (Allium amplectens), and yampah (Perideridia spp.) increase in abundance in the year following woody vegetation removal or prescribed fire (Jancaitis 2001). In addition, we have observed that some introduced invasive plant species, such as the ox-eye daisy (Chrysanthemum leucanthemum), show a great decrease in density of flowering plants the year immediately following a fire. While some introduced annual grasses (such as rattlesnake grass, Briza minor) and forbs typically increase in the first year following a bum, this is of less concern because the effect is temporary and is no longer evident by the second year. Patterns are also evident in the Willow Creek monitoring data at the level of guilds. For example, native perennial forbs, taken as a group, show consistent increased levels in the first year following a bum, while introduced perennial forbs generally show a pattern of decreased abundance in the first year following a bum. Woody plants, which have invaded into these native prairie remnants, have also been negatively affected by prescribed bums. Initial observations suggested that the bums are successful in killing a small percentage oftrees and shrubs outright, and also kill the above ground portions ofthe majority of shrubs and smaller trees, but are subject to resprouting from the stump. After repeated prescribed bums, tree stumps become sufficiently damaged that they may completely consumed by fire, resulting in an end to additional sprout production. In the last few years at Willow Creek, manual removal of woody plants has been implemented in conjunction with prescribed bums, to help speed progress toward achieving site management goals. Burning also appears to reduce the use of prairie habitats by meadow voles, which are small rodents that eat vegetation. During peak years of vole abundance (such as in 2001 and 2005), they can have substantial negative impacts on native prairie communities because of their herbivory (grazing) of 3