Vegetation and Land Cover, Bitter Creek National Wildlife Refuge

This map is based on interpretation of aerial imagery as well as field data collected by USFWS Refuge Planning staff and botanist Pam Devries. Detailed plant surveys were conducted throughout the growing seasons of 2009 and 2010 to determine the distribution of vegetation classes throughout the NWR. Mapping was done to the Group/Macrogroup level of the National Vegetation Classification System in most cases, with some classes mapped to the Alliance level, especially for isolated stands that were clearly identifiable. Class assignments were based on descriptions from A Manual of California Vegetation, Second Edition (Sawyer et al. 2008). Two dates (2009 and 2010) of near-infrared orthoimagery from the National Agricultural Imagery Program (NAIP) were used for classification. The methodology included segmenting imagery into homogeneous polygons using eCognition software. Classes were then assigned based on both spectral and textural characteristics. Manual editing was also performed to improve the accuracy of the classification. Validation was performed by collecting an additional set of field data following completion of the map. Over 300 points were used for the validation and the overall accuracy of the map was determined to be 77.5%.