As you travel east and into higher elevations, the forests begin to transition to a mixed conifer type, which is generally defined as Douglas-fir and/or true fir with pine and various hardwoods. Mixed conifer forests are pretty complex and can vary widely across the interior of the state, but thats another story.
Only the eastern and more remote portions of Humboldt county have these types of forests, though occasionally you may find islands of habitats that resemble mixed conifer and form unique areas on the landscape. (e.g. willow creek, south fork mountain, etc.) This place is near the pilot drainage and is nestled within a thousand acre oak woodland, where just about 10 acres have developed into this unique forest island.
Here is another example of what I would say was natural encroachment of oak woodlands, or better put, succession. There are a few aged white oak trees, but they are in severe decline. Most of the woody debris on the ground and standing snags are white oak, a last testament of what was there a few hundred years ago. This forest obviously developed with fire as all the trees have layers of fire scars, including this madrone.