Under contract to the California Department of Fish and Wildlife (CDFW), the North State Planning and Development Collective (NSPDC) created a fine-scale vegetation map of portions of the Sierra Nevada mountains around Lake Tahoe and the adjacent Modoc Plateau. CDFW’s Vegetation Classification and Mapping Program (VegCAMP) provided in-kind service to allocate and score the Accuracy Assessment.

The mapping study area consists of approximately 1.6 million acres, covering portions of Sierra, Plumas, Placer, Nevada, Modoc, and Lassen counties. Work was performed on the project between 2019 and 2023. The purposes of the project include assisting land managers in decision-making, fire and fuel management, protecting endangered species and habitats, protecting cultural and natural resources, habitat connectivity, habitat restoration, conservation prioritization, and informed development. NSPDC staff conducted 434 Rapid Assessment and Releve surveys across the mapping area in the summer of 2019 to gather vegetation data to be used in the development of a vegetation classification for the project area.

The vegetation classification used for mapping followed the guidelines set forth by the National Vegetation Classification System (USNVC 2019) and A Manual of California Vegetation (CNPS 2020).

The vegetation map was produced applying heads-up digitizing techniques using a 2018 base of one-meter National Agricultural Imagery Program (NAIP) imagery (true-color and color infrared), in conjunction with ancillary data and imagery sources. Map polygons are assessed for Vegetation Type, Percent Cover, Exotics, Development Disturbance, and other attributes. The minimum mapping unit (MMU) is 1 acre; exceptions are made for wetlands and riparian types, which were mapped to a 1/4 acre. Breaks on overstory cover were done at 3 acres.

Field reconnaissance and the Accuracy Assessment enhanced the overall map quality. There were a total of 107 mapping classes. The overall Fuzzy Accuracy Assessment rating for the final vegetation map,at the Alliance, Group, and Macrogroup levels, is 81.7% percent.

More information can be found in the project report, which is bundled with the vegetation map published for BIOS here: https://filelib.wildlife.ca.gov/Public/BDB/GIS/BIOS/Public_Datasets/3000_3099/ds3089.zip