One gravel road traverses Bear Valley, Bear Valley Road, which is accessed from the south by State Route 20. The soils of the valley are clay, supporting a herbland/grassland that is mostly grazed by cattle, and home to annual and perennial native wildflowers. Bear Valley is well-known for its springtime displays of wildflowers, and its large population of the Adobe Lily (Fritillaria pluriflora). March and April are the best months to visit Bear Valley, when the wildflowers are blooming in mass.
Bear Valley is an elongated north-south trending valley located adjacent to the Stony Creek Fault. The valley consists of Quaternary alluvium bounded by Mesozoic lower Cretaceous marine sedimentary rocks and the Knoxville Formation (Jennings 1960). The valley is drained to the south by Bear Creek. Annual precipitation ranges from 21 to 23 inches. The Bear Valley Fault divides that Bear Valley and Walker Ridge, trending on a north-south axis.
Unfortunately, Bear Creek is contaminated with mercury and methylmercury. "Bear Creek has had the highest concentrations of methylmercury in California streams where recreational fishing occurs, prompting the California Environmental Protection Agency in 2005 to issue a health advisory that no one should eat fish or shellfish from Bear Creek." (Colusa Resource Conservation District 2008.)
Walker Ridge geology consists of serpintine rock, which supports a special flora, one adapted to the harsh edaphic conditions created by the ultramafic rock. Late spring is a good time to botanize Walker Ridge.
George Clark studied the flora of Bear Valley and Walker Ridge for many years until his untimely death (while botanizing on Walker Ridge) in 1996. George and I compiled a list of all the vascular plants we observed in Bear Valley and on Walker Ridge, the results of which are provided in the Bear Valley flora (a checklist of plants) of the valley and adjacent ridge. The flora of this area consists of approximately 280 vascular plant taxa (including subspecies and varieties), complemented by lichens and bryophytes (mosses, liverworts, and hornworts). The flora is primarily holoarctic in floristic makeup, with a nearly direct topographic link to the Cascade Ranges to the north. The flora is also influenced by the Madro-tertiary flora from the south.
Of the 280 vascular plants on the checklist, 247 (88.2%) are native and 33 taxa (11.8%) are nonnative, significantly better than that for the flora of California as a whole, which has a 75%:25% native:nonnative ratio. This ratio tells us that the natural habitats have been little disturbed by human influences compared to many other areas of California. Very few vouchers for the vascular plant flora have been collected and deposited into public herbaria from the Bear Valley/Walker Ridge area. No surveys of the lichen or bryophyte floras of the area have been conducted, at least not that I am aware of anyway.
Map of Bear Valley and Walker Ridge
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