Wetlands of Crater Lake National Park: An assessment of their ecological condition

Adamus, Paul; Bartlett, Cheryl

Authors’ Summary: “This study sought to assess the health of wetlands in Crater Lake National Park (CRLA). To address this objective, during 2006 we visited and assessed the health of 76 wetlands throughout the park, covering an area equal to about 38% of the park’s known wetland area. Of the wetlands visited, 61 were selected using a statistical procedure that drew a spatially balanced randomized sample from an existing map of CRLA wetlands and 15 were selected to represent coarse scale attributes apparently absent from the 61 statistically selected sites. Among the visited wetlands, we surveyed a total of 101 vegetation plots. We also characterized soil profiles and observed surface hydrologic conditions. Before beginning the field work, we used GIS and a variety of existing spatial data layers to quantitatively characterize all mapped CRLA wetlands. Wetlands in CRLA occur in a variety of settings, including stream riparian areas, pond margins, alder covered slopes, springs, montane meadows, and snowmelt depressions. Although occupying less than 1% of the park’s area, these wetlands provide a variety of ecological services such as water storage, water purification, slope stabilization, carbon sequestration, thermoregulation, and support of plant and animal habitat and biodiversity. Many factors define wetland health (or integrity), including contaminants that could not be measured by this study. Only a few indicators of wetland health can be estimated rapidly and at reasonable cost across a large number of wetlands. One is the prevalence of native plant species, and from these data alone our data show most CRLA wetlands being relatively healthy. We found six nonnative plant species (<1% of all species we encountered) among 14 (18%) of the 76 wetlands we visited. From zero to four such species were found per wetland, but they never dominated the vegetation cover. Our assessment of just 76 wetlands detected two thirds of CRLA’s known wetland flora. Among the 354 plant taxa (both wetland and upland) that we found in the visited wetlands were 10 that are listed by the Oregon Natural Heritage Program as rare or having limited distribution. We also found 20 species and subspecies that had not previously been reported from the park. In most wetlands, more than 45 plant species and 21 families were found, and most of the 100 m 2 plots we surveyed had more than 24 species and 15 families, with a maximum of 51 species. All but six of the selected sites were confirmed to be wetlands. Although the primary objective of this project did not include wetland boundaries or comprehensively identifying previously unmapped wetlands, we did incidentally discover at least 16 wetlands outside the Crater Lake caldera and 28 within it that had not been previously mapped by the National Wetlands Inventory. Our onsite GPS measurements also indicated that the NWI had underestimated the spatial extent of many wetlands. We recommend further attempts be made to identify and assess wetlands in the northeastern portion of the park, and to survey more wetlands in parts of the Bybee Creek area that we could not reach during 2006 due to a forest fire at that time.”

Wetlands of Crater Lake National Park: An assessment of their ecological condition

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