The north unit of the monument contains three vegetative types that are notable for the diversity they contribute to the monument. Douglas-fir/mountain snowberry, upland quaking aspen, and riparian. The three types cover only 0.3% of the monument, but they provide important wildlife habitat. The Douglas-fir forest is found on relatively steep, north-facing slopes of older cinder cones and along Little Cottonwood Canyon. The quaking aspen groves are in upland sites away from permanent stream courses. The riparian zone is characterized by dense woody vegetation, proximity to a permanent watercourse, and a dense layer of tall forbs.