_Alnus rhombifolia_
_Quercus agrifolia_
_Ribes indecorum_
_Rhus integrifolia_
_Rhus ovata_
_Rhus trilobata_
This association is limited to the Pacific slope of the mountain range,
occurs in the mouths of canyons and on the floors of canyons, and
extends up the larger canyons to 4000 feet elevation or higher. In a few
areas on the flats at the coastal base of the range the oaks replace the
coastal sage.
The large oaks forming an overhead canopy and the lack of much
undergrowth give the oak woodland a shaded parklike appearance. Few
brushy or herbaceous plants grow in the mull-laden soil beneath the
oaks. Some grasses, however, are present locally.
Two habitats are found in the oak woodland: the pure oak woodland and
the riparian. Much of the oak woodland is in canyons and therefore near
streams or seepages. The larger streams have bordering growths of
alders, willows, and blackberries, inhabited by meadow mice and shrews
that are normally absent from the adjacent oak woodland. NEOTOMA
FUSCIPES MACROTIS and PEROMYSCUS CALIFORNICUS INSIGNIS are commonly
found in the riparian habitat, and _Peromyscus boylii_ probably reaches
peak abundance in the stream-side thickets and tangles of plant debris.
The rather open floor of the oak woodland is relatively devoid of mammal
life. _Peromyscus californicus_ and _Peromyscus boylii_, the only
ground-dwelling rodents commonly found here, usually are taken near the
limited areas of brushy growth, or the shelter afforded by logs and
fallen branches. The paucity of shelter for small mammals seems to be an
important factor limiting rodent populations in the oak woodland.
In the foothills of the San Gabriels the gray squirrel is restricted to
the oak woodland, even though this association may be represented by
only a narrow strip of canyon bottom oak trees. The presence or absence
of "bridges" of oak woodland between mountains which are centers of gray
squirrel populations and nearby ranges has probably been a major factor
influencing the present geographic distribution of this animal.
The raccoon is the most abundant carnivore of the oak woodland, being
especially common in the riparian habitat.