Mojave National Preserve (MOJA) is a large, 1.6-million-acre (650,00 hectares) unit of the National Park Service (NPS) that is located on the eastern California -Nevada border. The Preserve covers a vast expanse of the Mojave Desert ecosystem that includes a diverse mix of plant communities occurring on a very rugged and arid landscape. Contained within its borders are broad alluvial valleys, desert washes, playas, sand dunes, volcanic formations, domes, hills, and mountain ranges. Castle Mountains National Monument (CAMO) was recently added as a unit of the NPS in 2016 and is situated in the northeast corner of MOJA. CAMO encompasses about 21,000 acres (8,500 hectares) along the Nevada border supporting Joshua tree forests and unique mountain grasslands. To better understand and document the vegetation diversity occurring at both sites, the NPS, the National Vegetation Inventory Program (NVIP), and the NPS Mojave Desert Inventory and Monitoring Network (MOJN) started a vegetation inventory effort here in 2010.
Actual work began in 2011 on a ten-year, six-phase project with a review of the existing vegetation data, a summary of the previous classifications, and a work plan for the network were created. In phase two, the NPS, California Native Plant Society (CNPS) in conjunction with researchers from the University of Nevada, Las Vegas (UNLV) collected 630 classification plots and observation points across the landscape. Field data was then entered into the NVIP-specific PLOTS database along with an additional 588 samples from a variety of past studies. In phase three, CNPS analyzed the PLOTS data to classify 67 plant alliances and two landform types using the revised U.S. National Vegetation Classification (rUSNVC) standard. From this list, 136 plant associations were estimated to occur at MOJA and CAMO. During phase four, Cogan Technology, Inc. (CTI) created the digital vegetation map layer for the project that covered over 1.6 million acres (640,000 hectares). In the accuracy assessment (AA) phase, contracted field crews collected data at 720 AA point locations that were randomly placed by map class throughout the project area. In the final phase, CTI finalized the classification, reported the AA results, revised the final vegetation map, and delivered the final products to the NVIP.
The resulting spatial database and vegetation map layer were created using a combination of 2018 National Agriculture Imagery Program (NAIP) basemap data, ground-based verification efforts, and a two-step, or hybrid mapping approach that used both manual and automated techniques. By comparing the vegetation signatures on the imagery to the field data, 87 map units (72 vegetated and 15 land-use/land-cover) were developed and used to delineate the plant communities. The interpreted vegetation polygons were then digitized into a Geographic Information System (GIS) layer that was field-tested, reviewed, and revised. The final MOJA and CAMO vegetation map layer was assessed for overall thematic accuracy at 91% with a Kappa value of 92%.
Products developed for MOJA and CAMO are described and presented in this report and stored in the accompanying project digital files. Project deliverables include the final report, the spatial geodatabase, digital field photos, metadata, a classification report, and a field key to the vegetation alliances. For a full list of the MOJA and CAMO products to download please visit the National Park Vegetation Inventory Product website.
