 The mixed woodland region is a dense forest with many species of trees , located near the tops of the plateaus . The forest canopy shades the ground , resulting in a cooler temperature . The canopy also reduces the amount of water evaporation . California black oak , Douglas fir , Pacific madrone , incense cedar , and other plants grow in the mixed woodland . Shrubs such as Oregon grape , honeysuckle , blue elderberry , and Pacific poison oak also grow here . The soil in this area is mostly loam . 
