The mountain communities of southern California have evolved under conditions of high seasonal moisture and contrasting temperatures. These are similar to the conditions that exist in the northern coniferous forest which extends southward along mountain ridges of California and- Baja California. Winter temperatures are cold and the high precipitation frequently falls as snow. Summer temperatures are mild with moderate precipitation. Precipitation totals in southern California generally increase with higher elevations, due to the effect of adiabatic cooling.

In the winter this cooling occurs when warm, moisture-laden air from the Pacific Ocean is abruptly forced upward by the rapidly rising contour of the mountain ranges. As the air cools, it becomes saturated, thus forcing the moisture to fall as rain or snow. During the summer, especially in August and September, heavy rainfall is recorded in the mountain regions as a result of the movement of tropical air masses over them. Annual precipitation totals throughout the high country may be up to four or more times greater than in the nearby coastal lowlands. The influence of these climatic conditions along with the various structural features of land-form have determined the characteristics of community development.

Several sub-communities are recognizable in the mountainous regions of southern California, including the forested slopes, mountain riparian, mountain meadows, and alpine fell-fields.*

*Extracted Natural History of Southern California: Ancinec, Radford, Schwenkmeyer