As some of you may have observed, it’s not just the oaks that are suffering here in California. Problems are seen in the pines, the bay laurels, the sycamores, and the redwoods. Douglas firs are sick and dying in many places, especially towards the coast. Symptoms such as a thin canopy, a heavy cover of cryptogams (mosses and lichens), and bark deterioration are consistent with problems in soil fertility due to fire suppression and systemic acidification.
Fire mimicry methods were applied to these two sick Douglas fir trees in Woodside, California in May of 2007, with some additional work in 2008. Below are the photos showing the canopy changes after two years. Sorry, no control trees here, the owners rightly want to keep all their trees healthy.