|Santa Rosa Plateau|
April 19, 1997
At one time slated to be under housing and shopping centers, the
6,925 acre Santa Rosa Plateau
Ecological Reserve represents one of two remaining
strongholds for California's Engelmann Oak
(Quercus engelmannii). Once ranging
across southeast California, Arizona and Baja California
before the evolution of the modern Mojave and Sonoran deserts, climate change has clearly
narrowed the geographic distribution of this species. Today, however, the
most formidable threat
for this oak is urban/residential development. Not long ago, one could find this oak in areas like
Pasadena and Pomona. Most of these populations have
succumbed under the pressure of our ever
expanding city. 90% of remaining stands are found in San Diego County. Two substantial
populations occur around Black Mountain
(San Diego County) and the Santa Rosa Plateau.
While certainly survivors remain outside
these two locations, the vastness of the oak savannah in
southern California has been lost save within these last bastions of Engelmann oak
habitat (Pavlik, et al., 1991)
The oak savannah and woodland communities here are stellar, causing one to
the urbanization that presses near its boundaries. Another bonus found here are the springtime
vernal pools, another rapidly disappearing ecosystem of
Engelmann oak (Quercus engelmannii) and coast live oak (Quercus
agrifolia) mingle in this
hillside display. The silvery-blue/green foliage helps to distinguish the Engelmann species. I
delight in the range of hues within this small assembly of oak.
This most extraordinary cache tree ("granary") is in evident use
by an acorn woodpecker clan (Melanerpes formicivorus). While generally every
carefully hoarded acorn in these community
caches are consumed (making up to half of the acorn woodpecker's diet), some acorns evade
their ultimate fate by
sprouting and taking root in the decaying wood of a dead tree.
An overview of the Plateau
Indian milkweed (Asclepias eriocarpa)
Pavlik, Bruce M., Muick, P.C., Johnson, S.G., and Popper, M. 1991. Oaks of
California. Cachuma Press: Los Olivos.
Revised: January 5, 2003
This site ©2003 Ann Dittmer.