Olympic National Park vegetation classification and mapping project report

Nielsen, Eric; Copass, Catharine; Brunner, Rachel; Wise, Lindsey

doi:10.36967/nrr-2286420

The Vegetation Mapping Inventory (VMI) is an effort by the National Park Service (NPS) to classify, describe, and map vegetation communities present on NPS units across the United States. The Institute for Natural Resources, working in cooperation with the NPS North Coast and Cascades Network (NCCN), has completed a VMI project for the vegetation communities of Olympic National Park (OLYM). The map is based on a vegetation classification developed during the project and was created using an inductive modeling approach. Data used to construct the classification were collected between 2005 and 2015 and included plots from Mount Rainier National Park and North Cascades National Park Complex. These plots were used to develop and refine the association-level National Vegetation Classification (NVC). The associations were combined into map classes based roughly on the NVC alliance-level classification, but updated to allow improved map detail and accuracy. Model training data relied only on plots from OLYM, collected between 2005 and 2019. Independent field accuracy assessment data were collected in 2013 and applied to the final map generated later. The map development process was organized around the random forests machine learning algorithm. The modeling used 2,519 plots representing 150 vegetation associations and 50 map classes. Imagery from the National Agriculture Imagery Program and the Sentinel-2 and Landsat 8 satellites, airborne lidar bare earth and canopy height data, elevation data from the U.S. Geological Survey 3D Elevation Program, and climate normals from the PRISM Climate Group were used to develop a variety of predictor metrics. The predictors and the map class calls at each plot were input to a process in which each map class was modeled against every other map class in a factorial random forests scheme. We used the plot-level modeling outcomes and species composition data to adjust the crosswalk between association and map class so that floristic consistency and model accuracy were jointly optimized across all classes. The map was produced by predicting the factorial models and selecting the overall best-performing class at each 3-meter pixel. The final vegetation map, including a buffer surrounding the park, contains 43 natural vegetated classes, seven mostly unvegetated natural classes, and four classes representing burned areas or anthropogenic disturbance. Coniferous forests and woodlands cover four-fifths of the park, with nearly half that consisting of forests dominated by silver fir (Abies amabilis). Upper montane and subalpine forests and woodlands cover one-fifth, mostly surrounding Mount Olympus and on the east side of the park. Fourteen percent of the park is occupied by wet lowland forests in west-side valleys and on the coastal strip. Drier lowland forests are found mainly on the north and east sides and account for another thirteen percent. Broadleaf and mixed forests occupy less than three percent of the park, mostly in west-side river floodplains. Shrub-dominated and herbaceous vegetation each cover about four percent, mostly in avalanche tracks and as high-elevation dwarf shrublands and dry meadows. Sparsely vegetated and entirely bare rock cover six percent of the park; lake surfaces and exposed snow and ice round out most of the remaining three percent.

Olympic National Park vegetation classification and mapping project report

Series

See also

Collections