Vegetation - Orange County - 2012 [ds1336]

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 and 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 Agencys 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).

The Orange County mapping effort contains 85,705 acres and consists of two separate subregions, one located in the northern portion of the Santa Ana Mountains and adjacent inland portions of the coastal plain, the other to the south, which is located in the San Joaquin and Laguna Hills from Newport Beach south towards the town of Dana Point. The study is bisected by two ecological provinces as defined by the U.S. Department of Agriculture Ecological Sections of California. The Coastal Subregion falls entirely within 261B (Southern California Coastal Province) and the Central Subregion falls partially within the abovementioned Province while the higher elevation portions of this subregion just make it into M262B (Southern California Mountains and Valleys).

The initial steps of the mapping effort included the photo interpreters reviewing the study area for terrain, environmental features, and probable vegetation types present. Questionable photo signatures were noted so that they could potentially be visited while on the field reconnaissance trip, which took place shortly thereafter. After the field reconnaissance trips were conducted, the GPS waypoints, associated ground photos, and image based photo signatures were correlated. A preliminary vegetation mapping classification based on the NVCS was created from information gathered on the reconnaissance trip and discussions with NROC and CDFW ecologists. The preliminary floristic classification uses the approximately 200 ground based rapid assessment field plots collected in 2013 by AECOM Technology Corporation (AECOM 2013) and subsequently analyzed and classified by CDFW. Photo interpreters used the raw data collected from the rapid assessment plot gathering effort in addition to the preliminary keys and descriptions created by CDFW. The initial data-gathering phase of the mapping effort took approximately 2 months.

Production level delineations and labeling commenced following the correlation of the field reconnaissance data to the imagery and the subsequent development of photo interpretation and biogeographical descriptions of the types. Existing datasets depicting topography, climate and past vegetation gathering efforts aided photo interpreters in their delineations and floristic assignments during the production effort. The production level delineations and labeling effort took approximately 6 months.

During the mapping production effort, two ground based verification trips were undertaken which were designated to validate the general trends and models established by the photo interpreters in the course of the signature and model development phase of the project. Any erroneous assumptions were corrected during this effort and previous mapping was subsequently adjusted accordingly. The validation efforts and subsequent corrections took approximately 3 weeks, of which, 3 days were spent in the field.

The draft map product was subsequently delivered to CNPS for the final Accuracy Assessment (AA). Results from the AA effort were analyzed by photo interpreters and any ensuing questions were addressed by CDFW ecologists. A final AA database was delivered to AIS that was used to update the vegetation map. The incorrect calls to the mapped polygons were subsequently corrected to the ground based AA point. Additional corrections and refinements were made to other polygons that followed incorrect trends established from the AA database points.

DFW appreciates learning how our datasets are being used so that we can leverage support for classifying and mapping new areas and let users know of any updates. Please contact Diana Hickson by email (Diana.Hickson@Wildlife.ca.gov) or by phone at 916-327-5956.