Blue Oak Woodlands
Foothills east of Mount Diablo State Park
The blue oak woodlands are a mosaic of forest and savanna on the foothills of the Coast Ranges and Sierra Nevada, encircling the Central Valley of California. These beautiful woodlands are one of the largest ecosystems in California, but they are imperiled by agricultural development, suburbanization, and by the apparent decline in natural regeneration. Many of the remaining blue oak woodlands were never systematically logged and still contain canopy-dominant individuals that are 150- to over 500-years old. Our extensive field research and tree-ring dating indicates that literally thousands of acres of old-growth blue oak survive on private and public land. In fact, the remaining blue oak woodlands may be one of the most extensive old-growth forest types left in California. These ancient woodlands contribute to watershed protection and preserve an important component of the eroding biodiversity of California. The annual growth rings of these exceptional old age blue oak trees also record a detailed history of drought and wetness over California for the past 500 years. The University of Arkansas Tree-Ring Laboratory, in collaboration with colleagues at the Scripps Institution of Oceanography in La Jolla, the Western Regional Climate Center in Reno, and the Laboratory of Tree-Ring Research in Tucson, has initiated a long-term research project designed to map these widespread ancient blue oak remnants and to use non-destructive core samples for the reconstruction of precipitation, runoff, and water quality in the San Francisco Bay-Delta ecosystem. The CALFED Ecosystem Restoration Program and the National Science Foundation are funding this project.