Vegetation - Proposed Tehachapi Pass High Speed Rail Corridor [ds1328]

The Geographical Information Center (GIC) at California State University, Chico, completed a vegetation map of the Proposed Tehachapi Pass High-Speed Rail Corridor (HSRC), covering 199,493 acres. The project was funded by the Strategic Growth Council to support routing and mitigation planning for the high-speed rail system. The HSRC sits at the unparalleled convergence of four ecosystems – the Sierra Nevada, Sierra Nevada Foothills, Mojave Desert, and Great Valley ecosystems. Many vegetation types mix in a relatively small area as a result of this convergence. Because the timing of the project did not permit a full data collection and classification effort, we based the vegetation classification for the HSRC on the existing classifications from these four ecosystems. To set the mapping boundary through the Tehachapi Pass, a buffer of five miles was applied to the Highway 58 corridor between General Beale Road on the north side and the DRECP map boundary on the south side. The map was produced using heads-up digitizing based on 2012 National Agricultural Imagery Program (NAIP) imagery. The minimum mapping unit (MMU) is one acre for most vegetation types, with exceptions for important or special stand types. Although the primary purpose of the map is to document vegetation communities, it provides additional structural data such as herbaceous, shrub, and tree cover, and information about the level of disturbance within the vegetation stand. VegCAMP was tasked with the creation of the vegetation classification for the project area and collected 52 rapid assessments, 9 releves, and 226 reconnaissance surveys for the classification. GIC also collected an additional 574 reconnaissance for the mapping process. The vegetation classification follows the National Vegetation Classification Standard (NVCS), and in some cases includes types at the Association level. The classification analysis based on field survey data resulted in 73 Alliances (15 tree, 38 shrub, and 20 herbaceous) and 65 Associations (24 tree, 29 shrub, and 12 herbaceous). Once GIC completed a draft map of the HSRC, an accuracy assessment effort with field verification was conducted by VegCAMP staff to validate the vegetation map. The overall accuracy of the map exceeded the state standard of 80%. A total of 179 accuracy assessment points were collected, with a overall users' fuzzy-logic average accuracy score of 81.7% and a overall producers' fuzzy-logic average accuracy score of 83.5%.