Vegetation classification and mapping: Crater Lake National Park

DiPaolo, Dominic; Odion, Dennis; Rolih, Kathleen; Adamus, Paul; Sarr, Daniel

Crater Lake National Park is best known because it contains one of the world’s deepest, clearest, and thus, most iconic lakes. However, the great majority of the park is terrestrial, and there are considerable vegetative resources within the 73,775 ha (182,303 acre) Crater Lake National Park. To classify and map the vegetation at Crater Lake National Park, the Vegetation Mapping Inventory of the National Park Service funded an effort, beginning in 2010. Southern Oregon University staff performed the inventory work, while the Klamath Network Inventory and Monitoring Program coordinated the effort and provided additional funding along with computers, software, and other resources. To classify the vegetation, we sampled 499 plots (relevés) throughout the terrestrial portions of the park, and we included data from an additional 101 plots sampled during a wetland study conducted in 2006 (Adamus and Bartlett 2008). In each plot, all species present and their percent cover were enumerated. For safety and accessibility reasons, we excluded from sampling the steep, unstable Crater Lake caldera and areas outside the caldera where slopes were above 30%, or where roads or trails were nearby. We identified 387 vascular plant species in the relevé plots. We classified the relevé data into 80 plant associations. Forty seven plant associations were equivalent to associations in the U.S. National Vegetation Classification (USNVC). Twenty plant associations were being peer reviewed for inclusion in the USNVC at the time of the completion of this project. Thirteen of these associations were not equivalent to associations in the USNVC, and hence these were regarded as provisional associations. Most of the associations were not distinct enough on the imagery to be mappable. Instead, we mapped 28 broader vegetation/landcover types (map units) that were visible on the imagery that we used: 2011 National Agriculture Imagery Program (NAIP) true color and infrared imagery, as well as Light Detection and Ranging (Lidar) imagery. The 600 relevé data points, as well as 803 on the ground validation plots, were instrumental to the mapping process. Google Earth imagery, which provides oblique viewing angles, and online Environmental Systems Research Institute (ESRI) imagery were also consulted. For each polygon we labeled the map unit and one or two floristic associations that occurred within the polygon. We describe the map units in detail in Appendix A. Our final map product is a geographic information system (GIS) database of vegetation structure and composition across the Crater Lake National Park terrestrial landscape, including wetlands. The database includes photos we took at all relevé, validation, and accuracy assessment plots, as well as the plots that were done in the previous wetlands inventory. We conducted an accuracy assessment of the map by evaluating 698 stratified random accuracy assessment plots throughout the project area. We intersected these field data with the vegetation map, resulting in an overall thematic accuracy of 86.2 %. The accuracy of the Cliff, Scree & Rock Vegetation map unit was difficult to assess, as only 9% of this vegetation type was available for sampling due to lack of access. In addition, fires that occurred during the 2017 accuracy assessment field season affected our sample design and may have had a small influence on the accuracy. There have been several fires that occurred since 2011 when the imagery used for mapping was produced. The portion of these fires that burned at high severity (i.e., where above ground vegetation was mostly killed) have experienced dramatic change that could not be documented using our imagery, and therefore are not captured by our mapping. Many of these areas are now early successional forms of the preburn vegetation, however that cannot be determined from our map. Thus, the user is advised that our vegetation map be used in concert with an overlay of high severity burned patches.

Vegetation classification and mapping: Crater Lake National Park

Series

Collections