Dash logoUC Irvine logo

Vegetation Classification for the Nature Reserve of Orange County

Citation

AECOM; Aerial Information System, Inc.; California Native Plant Society (2016), Vegetation Classification for the Nature Reserve of Orange County, UC Irvine Dash, Dataset, https://doi.org/10.7280/D1F30C

Abstract

The ultimate goal of this project is to create an updated fine‐scale vegetation map for about 58,000 acres of Orange County, consisting of the 37,000‐acre Orange County Central and Coastal Subregions Natural Community Conservation Plan (NCCP)/Habitat Conservation Plan (HCP) Habitat Reserve System; approximately 9,500 acres of associated NCCP/HCP Special Linkages, Existing Use Areas, and Non‐Reserve Open Space; and approximately 11,000 acres of adjoining conserved open space (study area). The project consisted of three phases.
Phase 1: To update vegetation mapping, the Natural Reserve of Orange County (NROC) proposes to use Manual of California Vegetation (MCV) methods (2009), which will be implemented in two stages: Stage 1 – Development of a vegetation classification system for the Central and Coastal Subregions of Orange County that is consistent with the MCV. Stage 2 – Application of the vegetation classification system to create a vegetation map through photointerpretation of available aerial imagery and ground reconnaissance. The MCV methods were developed by the California Department of Fish and Game (CDFG) Vegetation Classification and Mapping Program in collaboration with the California Native Plant Society (CNPS). This approach relies on the collection of quantifiable environmental data to identify and classify biological associations that repeat across the landscape. For areas where documentation is lacking to effectively define all of the vegetation patterns found in California, CDFG and CNPS developed the Vegetation Rapid Assessment Protocol. This protocol guides data collection and analysis to refine vegetation classifications that are consistent with CDFG and MCV standards. Based on an earlier classification by Gray and Bramlet (1992), Orange County is expected to have vegetation types not yet described in the MCV. Using the MCV approach, Rapid Assessment (RA) data was collected throughout the study area and analyzed to characterize these new vegetation types or show concurrence with existing MCV types.
Phase 2: Aerial Information Systems, Inc. (AIS) was contracted by the Nature Reserve of Orange County (NROC) to create an updated fine-scale regional vegetation map consistent with the California Department of Fish & Wildlife (CDFW) classification methodology and mapping standards. The mapping area covers approximately 86,000 acres of open space and adjacent urban and agricultural lands including habitat located in both the Central and Coastal Subregions of Orange County. The map was prepared over a baseline digital image created in 2012 by the US Department of Agriculture – Farm Service Agency’s National Agricultural Imagery Program (NAIP). Vegetation units were mapped using the National Vegetation Classification System (NVCS) to the Alliance level as depicted in the second edition of the Manual of California Vegetation (MCV2). One of the most important data layers used to guide the conservation planning process for the 1996 Orange County Central & Coastal Subregion Natural Community Conservation Plan/Habitat Conservation Plan (NCCP/HCP) was the regional vegetation map created in the early 1990s by Dave Bramlett & Jones & Stokes Associates, Inc. (Jones & Stokes Associates, Inc. 1993). Up until now, this same map continues to be used to direct monitoring and management efforts in the NCCP/HCP Habitat Reserve. An updated map is necessary in order to address changes in vegetation makeup due to widespread and multiple burns in the mapping area, urban expansion, and broadly occurring vegetation succession that has occurred over the past 20 years since the original map was created. This update is further necessary in order to conform to the current NVCS, which is supported by the extensive acquisition of ground based field data and subsequent analysis that has ensued in those same 20 years over the region and adjacent similar habitats in the coastal and mountain foothills of Southern California. Vegetative and cartographic comparisons between the newly created 2012 image-based map and the original 1990s era vegetation map are documented in a separate report produced by the California Native Plant Society at the end of 2014.
Phase 3: The California Native Plant Society (CNPS) Vegetation Program conducted an independent accuracy assessment of a new vegetation map completed for the natural lands of Orange County in collaboration with Aerial Information Systems (AIS), the California Department of Fish and Wildlife (CDFW), and the Nature Reserve of Orange County (NROC). This report provides a summary of the accuracy assessment allocation, field sampling methods, and analysis results; it also provides an in-depth crosswalk and comparison between the new map and the existing 1992 vegetation map. California state standards (CDFW 2007) require that a vegetation map should achieve an overall accuracy of 80%. After final scoring, the new Orange County vegetation map received an overall user’s accuracy of 87%. The new fine-scale vegetation map and supporting field survey data provide baseline information for long-term land management and conservation within the remaining natural lands of Orange County.
Data made available in the OC Data Portal in partnership with UCI Libraries.

Methods

The project consisted of three phases, each with its own methodology.
Phase 1: To update vegetation mapping, the Natural Reserve of Orange County (NROC) usedManual of California Vegetation (MCV) methods (2009), which will be implemented in two stages: Stage 1 – Development of a vegetation classification system for the Central and Coastal Subregions of Orange County that is consistent with the MCV. Stage 2 – Application of the vegetation classification system to create a vegetation map through photointerpretation of available aerial imagery and ground reconnaissance.
Phase 2: Aerial Information Systems, Inc. (AIS) was contracted by the Nature Reserve of Orange County (NROC) to create an updated fine-scale regional vegetation map consistent with the California Department of Fish & Wildlife (CDFW) classification methodology and mapping standards.
Phase 3: The California Native Plant Society (CNPS) Vegetation Program conducted an independent accuracy assessment of a new vegetation map completed for the natural lands of Orange County in collaboration with Aerial Information Systems (AIS), the California Department of Fish and Wildlife (CDFW), and the Nature Reserve of Orange County (NROC).
For more detailed methodology information please consult the README.txt file included with dataset.

Funding

California Department of Fish and Wildlife, Award: Local Assistance Grant #P1082023

Location

SW 33.643, -117.981
NW 33.85, -117.555
Orange County (Calif.)