Northern Channel Islands Vegetation Inventory

The CNPS Vegetation Program has been collaborating with the National Park Service (NPS) since 2012 to categorize and describe the vegetation of the northern Channel Islands. The Channel Islands, consisting of eight islands off the southern California coast, are known for their uncommon plants endemic to one or more of the islands. While some of the native vegetation has been adversely affected by decades of grazing by animals introduced after settlement, it is now recovering after removal of these animals.

The unique southern California and island flora makes for some interesting vegetation patterns. One alliance, which is known from limited occurrence on the mainland in the Nipomo Dunes and Santa Monica Mountains within 2 km of the ocean, is the Coreopsis gigantea alliance. Giant coreopsis (called Leptosyne gigantea in the Jepson Manual) is a drought-deciduous shrub that sprouts yearly from thick branched stalks. We’re describing two new associations for this alliance. Photos from visits to San Miguel Island in early spring 2014 and 2015 show variation in rainfall between the two years.

Another unusual vegetation type is dominated by prostrate chamise, which is considered a variety of the common chaparral plant Adenostoma fasciculatum and is therefore placed within the same alliance. As the photo from Santa Rosa Island shows, it often grows below knee height. The most common associate of prostrate chamise on the northern Channel Islands is the endemic Quercus pacifica, or island scrub oak.