In light of some of the commentary regarding the recent effort by the USFS to plant trees within the Station Fire scar, I wanted offer some information regarding the history and ecology of the Angeles National Forest.
NOT A FOREST
Calling the Angeles National Forest (and especially that portion within the San Gabriel Mountains) a “Forest” is really a misnomer. The region is actually dominated by native shrublands, particularly chaparral. This is why we (the California Chaparral Institute) have proposed changing the name to the Angeles National Chaparral Recreation Area to better reflect what’s there and how the land is used. There are obviously lots of trees at higher elevations, but they really represent isolated “sky islands” of habitat that have been slowly reduced because of climate change over the past 14 million years. With the influence human activity on climate, this displacement has been accelerating over the past 100 years. The Station Fire, as unfortunate as it was, merely accelerated a change that has been occurring for a very long time.
FIRE & PEOPLE
Whenever the first humans arrived on the North American continent (there is strong evidence that a large contingent entered at least 11,000 years ago), their numbers were probably not significant enough to have a meaningful impact on the landscape until 5,000 years ago. However, once established, early Native Americans sometimes burned chaparral in an effort to increase favored natural resources (herbaceous seed crops and deer), reduce grizzly bear contact (chaparral was their favored habitat), and as a weapon against tribal enemies. To a limited degree, Spaniards continued the practice in order to expand grazing land. Once Americans arrived on the scene, fires caused by ranchers, miners, and hunters became so frequent the United States government recognized something needed to be done to protect valuable watersheds. US. Forest Reserves were first established in 1891 in part to address this concern. On December 20, 1892, the boundaries of the first reserve in California were drawn in the San Gabriel Mountains above Los Angeles, becoming part of the Angeles National Forest in 1908.
PAST REFORESTATION EFFORTS
The current reforestation effort is not the first in the San Gabriels. During the 1920’s over a million conifers, a substantial share of which were non-native, were planted in the San Gabriel Mountains. Most were eventually killed by fire or drought, finally convincing foresters that chaparral, not forest, was the most sustainable plant community in the area. The current USFS effort to plant trees failed to fully consider the implications of this history.
SHRUBLANDS ARE THE NATURAL CONDITION
The belief that shrublands are not the natural state of most of the Angeles, especially the San Gabriels (photo below), is not supported by historical, geological, or biological research. The conflict some appear to have with the data may be a matter of location or time. Although Coulter pines and pinyons grow below the 5,000 foot level, most of the region’s pines do not. Big-cone Douglas fir’s are generally restricted to extremely steep canyons in association with chaparral and oaks. Elevation and the limiting factors of moisture and soil type are the main reasons why about 75% of the Angeles National Forest is not forest, but primarily shrubland. It is not biologically possible for forests to exist in most of the region. However, during the late Pleistocene (28 to 50,000 years ago), forests were indeed much more prevalent. Based on pollen studies it has been suggested that plant community distribution (forests for example) dropped in elevation as much as 2,700 feet because of lower temperatures and higher rainfall than we have today.
Unfortunately, there are not many pollen studies for Southern California or historical records on conifers in the region for that matter. But there a few papers available that can provide some good background on the past and current condition of the Angeles National Forest. We have uploaded them on our website so they can downloaded easily. The last paper is linked to the USFS site.
Minnich, R.A 2007. Southern California conifer forests. Pages 339-366 in: M.G. Barbour, T. Keeler-Wolf, and A.A. Schoenherr (eds.), Terrestrial Vegetation of California, 3rd edition. University of California Press, Berkeley.