Sierran forest is the bioregion that overlooks the Kern River Valley. This bioregion reaches its terminus in the mountains just south and east of the Kern River Valley. It begins at an elevation of about 4,000 feet in the Greenhorns and Breckenridge Mtn., 5,500-feet in the Piute Mtns. and 6,000-feet on the Kern Plateau. Sierran Forest is actually a complex of several types of forest; ponderosa pine, Jeffrey pine, red fir, and giant redwood forest. It also contains many other species of tree, shrub, and herbaceous perennial and annual plants found only within the Sierran forest. 

The Greenhorn Range is a gently sloping mountain range to the west of the Kern River Valley. It is the southern end of the Sierra Nevada Mountains. At the southern end of the Greenhorns, ponderosa pine forest separates from the lower elevation oak woodland at around 4,000 feet and is found throughout the Greenhorns but gradually is replaced by Jeffrey pine at higher elevations. At about 7,500 feet the southernmost red fir forest is found in northern Kern County. Continuing north the Greenhorn Mountains merge with the Great Western Divide where 125 Giant Redwood trees stand sentinel at the Trail of 100 Giants.

The Kern Plateau climbs rapidly from the Kern River Valley and is cut by the North and South Forks of the Kern River.  It overlooks the Kern River Valley at its north end. This region is truly a remarkable botanical region, according to Ernest Twisselman's " A Botanical Scanning of the Kern Plateau," the area demonstrates a northern progression of flora. The rapid elevation climb gives way to several distinct forest communities. At the lowest elevation, the desert like pinyon woodland gives way to Jeffrey pine forest  which gives way to red fir forest which give way to lodgepole pine forest which gives way to the highest elevation alpine community. These transitions are quite evident in this amazing region strewn with meadows.

The eastern edge of the Kern Valley shows the deceptively dry Piute Mountains. At around 5,500 feet the dry chaparral and cypress covered slopes change dramatically. This forest consists of ponderosa pine, Jeffrey pine, and white fir. Several summer mountain communities are found nestled within this hidden treasure of Kern County.

Breckenridge Mountain stands guard as the southern boundary of the Kern River Valley. A beautiful relict Jeffrey pine forest is found beginning at 4,000 feet. The best example of this forest is found along the road leading to Breckenridge Campground. In the summer high clearance vehicles can drive all the way to the top of this 7,500' high mountain. Climb to the Forest Service fire lookout and you can view the entire Kern River Valley and the surrounding mountains.