More results from oaks in Fairfax, CA

More results of fire mimicry treatments of coast live oaks in Fairfax, CA after nearly two years. Several of these oaks have stem canker infections, probably Sudden Oak Death. Still . . .

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Four-year results of fire mimicry treatments of oaks in Fairfax, CA

Four years ago I began fire mimicry treatments on a grove of coast live oaks in Fairfax, CA. Several of these oaks are infected with stem canker disease, probably Sudden Oak Death. As you can see most of the oaks, as indicated by the size and fullness of their canopies, have responded nicely to the treatments.

Fire mimicry/canker surgery results with oaks in Fairfax, CA

In July of 2016 I began fire mimicry treatments on several coast live oaks in Fairfax, CA. Here are photos showing the response of the oaks after two years. As you can see most of the oaks are showing noticeable improvement in canopy greenness and density.

One of the oaks (Case No. 20160722.4 – see below) had two stem canker infections, probably Sudden Oak Death, that were surgically removed and cauterized in 2016. The last two photos below show the healing of the wounds, both on the same tree. There appears to be no sign of a lingering infection. It’s still too soon to say for sure if the procedure has worked, but the healing results so far are better than expected.

Do lichens play a role in oak decline?

(image downloaded from web June 2013)

Any careful observer of oaks in California cannot help but notice a dense covering of lichens growing on the trunks and branches of many of the trees. In some cases, the biomass of lichens in the canopy rivals and even exceeds the biomass of the oak foliage. Under extreme conditions of lichen cover, the oaks appear sickly and in decline.

Coast live oaks covered in epiphytic Usnea and Ramalina lichens. (February 2018, Aptos, CA)

There is a popular meme in naturalist and conservation circles that lichens do not harm trees and merely use them for support. Adherents to this ‘harmless lichen’ meme point out that lichens are photosynthetic and, thus, do not draw any resources from the trees. Some note that lichens support nitrogen-fixing bacteria, which can add to the nutrient pool and benefit the trees. Furthermore, lichens are known to be highly sensitive to air pollution, so the presence of abundant lichens in a tree is a sign of good local air quality.

I have long been doubtful about the science behind this meme. As an experienced researcher of forest decline I have frequently noted that sick and dying trees often have a dense growth of lichens in their canopies. Defenders of the ‘harmless lichen’ meme describe this as the opportunistic growth of lichens on sick trees, as the reduced foliage allows for additional light for the lichens to grow. It is certainly true that lichens benefit from sick trees in this way, but I believe that lichens are not merely innocent bystanders or benefactors in the demise of a tree.

Oak rescue status: Year 4

Four years ago I was contacted by some concerned folks about a very sick oak on their property in Carmel, CA. When I inspected the oak in 2014 I told the owners that I did not think it could be saved, but offered to do what I could to help if they so desired. Fortunately, the owners agreed, and after several years of fire mimicry treatments this coast live oak is showing clear signs of recovery. Note that the current photos show the oak after most of the dead branches have been recently pruned, and the light conditions are different. Still, it is clear to me that this oak is showing significant improvement in canopy density. My lesson here is to trust the property owners and simply do what I can to help the oaks, no matter how futile I think the attempt may be,