Wednesday, November 4, 2009
Convention Center, Exhibit Hall BC, Second Floor
The Rodeo-Chediski Wildfire - the largest in
Arizona’s history - damaged or destroyed ecosystem resources and disrupted ecosystem functioning in a largely mosaic pattern throughout the ponderosa pine forests exposed to the burn. Soil erosion and other ecosystem of this wildfire were studied on two watersheds; one burned by a high severity (stand-replacing) fire, and the other burned by a low severity (stand-modifying) fire. The Rodeo-Chediski Wildfire disrupted the ecological functioning on much of the 189,015 ha impacted by the fire. Plant communities included chaparral shrub communities and pinyon-juniper woodlands at lower elevations and ponderosa pine forests at high elevations. About one-half of the total area that was burned by the Rodeo-Chediski Wildfire experienced a high-severity fire, other areas burned at a low- to medium-severity fire, and still other areas were largely unburned. An assessment of the impacts of the Rodeo-Chediski wildfire on soil erosion was carried out on two watersheds situated at the headwaters of the Little Colorado River. One of the watersheds experienced a high severity burn and the other a low-to-medium severity burn. Estimates of soil erosion on a watershed-basis and relative to physiographic characteristics on the two watersheds following the high-intensity summer monsoonal rains and low-intensity winter precipitation and spring snowmelt-runoff events are presented and compared with estimates of soil erosion following other wildfires in the region. The wildfire changed plant species compositions and impacted the production of herbaceous plants. Effects of the post-fire vegetation changes reduced the capabilities of watersheds to support livestock but temporarily increased the use by other larger herbivores in the region. A long time (>200 years) will probably be required for severely burned areas to recover than those areas burned by at a low severity. Portions of the latter have already returned to pre-fire conditions.