Item 3: PH on Ordinance Prescribed Wetland Management Burning

Home Browse Search

USE OF PRESCRIBED FIRE IN WILLAMETTE V ALLEY NATIVE PRAIRIES Edward R. Alverson The Nature Conservancy Kalapuya hunted game such as deer and elk, and gathered food plants from the native flora. The prairies provided the majority oftheir food plants, including camas (Camassia spp.) bulbs, yampah (Perideridia spp.) roots, and tarweed (Madia spp.) seeds. Though they were not farmers in the conventional sense, they used fire to maintain habitats for valued food plants just as a farmer tills and plants a field to produce a crop. In addition, the may have found fire useful in hunting game, by attracting animals to browse on the fresh green growth that emerges soon after a fire. During the millennia that the Kalapuya people (presumably) subjected the Willamette Valley to fires, a diverse flora and fauna evolved that had appropriate adaptations to avoid, withstand, or even become dependent fire to maintain suitable habitats. In some cases, these were animal and plant species occurring nowhere else in the world except the Willamette Valley. Thus it was a "natural" landscape shaped (most likely) by human-set fires that the first explorers and settlers encountered in the early 1800's (Habeck 1961, Johannessen et al. 1970, Towle 1974). Morris (1934), Johannessen (1971) and Boyd (1986) document this practice through reviews ofthe early explorers and missionaries journals (David Douglas-1826, John Work-1834, C. Wilkes-1845, B. Hines-1881, etc.). These records report that fires were set annually in late summer and early fall, and covered extensive portions of the Willamette Valley. The main difficulty with the historic record is that it does not clearly describe how often presettlement fires returned to any given location, and that is a pertinent question that cannot necessarily be determined from the historical record (Whitlock and Knox, 2002). Drastic population declines resulting from introduced diseases, and ultimately, the removal of the Kalapuya Indians to the Grand Ronde Reservation halted wide scale burning in the Willamette Valley in the 1830's and 1840's. Without fire, wet prairies that have been left undisturbed have in many cases gradually changed into ash forests, while the drier prairies and savannas have succeed to oak woodlands and maple and Douglas fir forests. 2. Fire Effects Having established that fires likely were a significant feature of the presettlement landscape, scientists began developing hypotheses regarding the specific roles that fire plays in maintaining prairie habitats. Historical analyses of vegetation change at individual sites led to the development of a number of hypotheses, including: 1) Fires occurring at frequent intervals maintained open prairie habitats and prevented colonization of trees and shrubs on sites where they would be able to occur if fire was excluded; 2) Many herbaceous prairie species may possess tolerance or even adaptation to fire as a frequent influence; and 3) Some non-native plant species, particularly those coming from regions where fires do not occur, may be negatively affected by fire. Thus, implementing prescribed fires could potentially reduce cover of invading woody plants, enhance the populations of native plant species, and help reduce the abundance of some undesirable 2