Item 2: Ordinance on West Eugene Wetlands Burn Ban Exemption

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USE OF CONTROLLED ECOLOGICAL BURNS IN WILLAMETTE VALLEY NATIVE PRAIRIES Edward R. Alverson The Nature Conservancy May 2011 Controlled ecological burning involves the controlled use of fire as a management tool in natural areas. Scientists have been using controlled burns throughout the Willamette Valley to meet natural area conservation objectives and habitat restoration goals. The purpose of this paper is to provide historical background and ecological information to better understand why controlled ecological burns are considered to be so essential to natural area management in the Willamette Valley. 1. Natural History and Role of Fire in the Willamette Valley The first explorers and settlers who arrived in the Willamette Valley in the early 1800's described the Willamette Valley as supporting extensive areas of prairie and oak savanna. Land surveys conducted by the General Land Office of the US Government in the 1850's documented that about 1 million acres of the Willamette Valley were prairie lands at that time (Christy and Alverson, in press). These native prairie and oak habitats have been greatly reduced in extent due to agriculture, grazing of domestic livestock, residential and urban development, and expansion of forest vegetation into former prairies. Only small remnants of high quality native prairie and savanna are known to currently exist in the Willamette Valley at present. The exact number of remaining acres has not been documented, but the reduction from the original extent has been estimated to be close to 98%. The exact details of how the prairies and savannas originally became established are uncertain. The prairies may have become established during a time when the climate was warmer and drier than today (Hansen 1942, Walsh et al. 2010). At present, the climate of the Willamette Valley is sufficiently cool and moist to support forest vegetation on most sites in the absence of disturbance, but prairie or savanna may have been the "climax" vegetation at an earlier time when the climate was warmer and drier than today. However, there is some evidence that the extensive prairies and savannas were maintained, if not actually created, by fires set by Native Americans. Studies documenting pollen deposits in the Willamette Valley since the end of the ice age has shown a positive correlation between increases in grass pollen and increases in charcoal contained in the sediments at certain times in the past (Walsh et al. 2010). This suggests the possibility that prairies and savannas may have been created or maintained by human-set fires, since the incidence of lightning-caused fires in the Willamette Valley is generally low. More studies are needed to provide greater understanding of how prairies and savannas came to dominate the Willamette Valley in prehistoric times, but many researchers today believe that fire played a significant role. The Kalapuya Indians had abundant motivation to use fire in the landscape (Boyd, 1999). d d 1