Distribution and Community Associations of Cape Ivy (Delairea odorata) in California

Abstract

Cape ivy (Delairea odorata Lem.) was found to occur throughout coastal California and southern Oregon. It was most abundant in urbanized coastal areas such as the San Francisco Bay, and Santa Cruz, Monterey, San Luis Obispo, Santa Barbara and Los Angeles counties. Field observations showed Cape ivy to occur in seven different broad community types, including both riparian and non-riparian areas. Of the two morphological forms, the exstipulate type occurred more frequently at the northern and southern ends of the distribution, and the stipulate type was more common in the middle of the distribution range, from southern Humboldt County to Los Angeles County. Only 21 locations were found that supported both stipulate and exstipulate plants, and they were most often located in urbanized coastal areas. Analysis with GIS determined the elevation, temperature and precipitation ranges that Cape ivy occupies in California. The analysis indicated that Cape ivy occurs at elevations between 0 and 891 meters, annual mean temperatures between 10.5 and 17.7°C, and in areas with annual precipitation ranging between 232 and 2270 mm. An overlay analysis of Cape ivy locations using GIS was also compared with the California Natural Diversity Database sensitive species location information to determine which species might be threatened by Cape ivy expansion. Three sensitive animals and five sensitive plants were expected to have >40% of their occurrences with a 500 m buffer to Cape ivy infestations.