Wednesday, 19 November 2003: 2:30 PM
Effects of fire on the biota of high-elevation lakes in the Oregon Cascade Range
In 1996, a late-season wildfire burned approximately 4,000 hectares in the central Oregon Cascades. The burned area and neighboring unburned areas contained numerous lakes in a relatively uniform physiographic setting. This situation provided a unique opportunity to evaluate the effects of fire on lakes, and beginning in July 1997, we sampled 32 lakes (16 lakes in areas that had been intensely burned and 16 in unburned areas). Sampling was focused on small lakes (<1.5 hectare surface area) without fish populations. Physical, chemical, and biological (phytoplankton, zooplankton, and amphibians) data were collected during each of two sample periods, approximately one month apart. Although there was little sign of recovery of terrestrial vegetation during 1997, riparian areas surrounding the study lakes were flourishing. Comparisons of lakes from inside and outside the burned area suggest no statistically significant differences in density of phytoplankton or zooplankton, and amphibians were found in all of the lakes despite the effects of fire on the upland portions of the watershed. Variations in biota among lakes appeared to be related to local environmental factors of individual watersheds. These observations underscore the importance of small lakes as potential short-term refugia for aquatic organisms from the direct effects of fire and other natural disturbances.