From the Tehachapis to Tehama County, blue oaks and valley oaks are responding to drought-like conditions in the Sierra Nevada the way nature intended them to -- by dropping their leaves to conserve moisture.

"Normally, deciduous oaks don't begin changing color and losing their leaves until November, when short days and cold temperatures signal that winter is coming and it's time to go dormant," said Doug McCreary, a University of California natural resources specialist who has been studying oaks at the UC Sierra Foothill Research and Extension Center for nearly 20 years.

"People are concerned that what they are seeing is sudden oak death, but the fungus-like disease that is killing coast live oaks and tanoaks in the Coast Range has not been found in the Sierra."

Last winter was fairly dry, McCreary said. Oaks respond to drought with built-in defense mechanisms. Similar early leaf drops occurred during prolonged droughts in both the mid-1970s and late 1980s.

Most trees that lose their leaves early this year will probably recover during the winter and leaf out normally. Drought does stress trees, however, and stressed trees usually grow more slowly and may become more susceptible to insect and disease attacks.

For more information about California oaks, visit the UC Integrated Hardwood Range Management Program website at http://danr.ucop.edu/ihrmp/. For the latest information about sudden oak death, visit the website for the California Oak Mortality Task Force: http://www.cnr.berkeley.edu/comtf/.