Vegetation Cover Types and Habitats - 2007
Environmental Report Section 10.10.1.1
Monitoring plant communities and vegetation cover types on the Hanford Site focus on two main objectives: 1) mapping the distribution and extent of major plant cover types on uplands and riparian areas at the site and 2) conducting periodic surveys to assess whether community composition and structure are changing. Mapping the distribution and extent of vegetation on the site provides important information on potential and existing habitats of sensitive or rare species, as well as information regarding the presence of potential receptor species. Significant changes to the vegetation cover and habitats on the Hanford Site occurred during the past year as a result of several wildfires that burned on the Hanford Reach National Monument and across the central part of the Hanford Site. Lightening-caused fires burned on the Hanford Site during July 2007, and two fires were caused by human activities in August 2007.
On July 13, 2007, three lightning-caused wildfires merged and became known as the Overlook Fire that covered 8,527 hectares (21,071 acres) on the east side of the Columbia River on Hanford Reach National Monument lands. The Overlook Fire burned native shrubland and grasslands in areas on the Wahluke Slope. Lightening also started several small (less than 40.5 hectares [100 acres]) fires on the west side of the Columbia River that were quickly contained. On August 13, 2007, the Milepost 17 fire started along Highway 240 and burned about 1,905 hectares (4,708 acres) in a crescent-shaped area on the Fitzner/Eberhardt Arid Lands Ecology Reserve. The Wautoma Fire started on August 16, 2007, on private lands and burned across the Fitzner/Eberhardt Arid Lands Ecology Reserve onto the central Hanford Site. These two fires burned approximately 31,161 hectares (77,000 acres) of private and federal lands. About 26,709 hectares (66,000 acres) burned on the Fitzner/Eberhardt Arid Lands Ecology Reserve and approximately 3,116 hectares (7,700 acres) burned on the central Hanford Site (Figure 10.10.1).
The extent and effects of these large wildfires on vegetation and habitats are monitored and mapped using several types of tools. In addition to ground-based surveys, satellite imagery was used to map the burned area extent on the Hanford Site in 2007. Work will continue during 2008 to map changes in habitats and vegetation associations as a result of past wildfires.
Numerous activities associated with cleanup, including excavation, remediation, and restoration, have influenced the vegetation inside the areas and at their fenced boundaries. Information from ground-based surveys is used to update maps depicting areas with highly valued biological resources (http://www.pnl.gov/ecomon/Veg/Veg.asp). Periodic surveys of the frequency, cover, and number of species found on permanent monitoring plots provide information on trends or changes in species diversity, presence of invasive and key species, and the overall condition of the plant community and available habitat (PNNL-16623). Additional 2006 aerial imagery was obtained in 2007 and will be used in 2008 to update and complete a data layer describing shrub canopy cover across the Hanford Site.
