Do lichens play a role in oak decline?

20 07 2018
Lichens in tree

(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.

Lichens in oak

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. Read the rest of this entry »

Advertisements




Oak rescue status: Year 4

13 07 2018

Slide1

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,





Happy Earth Day 2018!

22 04 2018

Happy Earth Day from Sudden Oak Life! A hopeful message from the oaks . . .

Slide03

Slide04

Slide02 Read the rest of this entry »





Declining oaks in Marin respond to fire mimicry

20 04 2018

Slide1

As you may know many of the coast live oaks in Marin County, California are in severe decline. Here are examples of two oaks in Marin County, one in Mill Valley and the other in Larkspur, which were seriously ill upon my initial inspection. The oak in Larkspur was infected with a stem canker disease (probably Sudden Oak Death). Both trees have received fire mimicry treatments for several years, and the owners are pretty happy with the results.

With all the talk of exotic diseases, insect pests, and climate change being the main culprits of forest decline in California and elsewhere, here I show evidence that the real problem is that we are no longer tending our trees. In the words of M. Kat Anderson – “nature misses us”. Solutions are at hand, and they are not difficult to implement.

Slide2

Slide1 Read the rest of this entry »





Fire mimicry results from Mill Valley and Los Altos, CA

8 03 2018

Slide1

Slide2

The first two photo sets above are of an oak in Mill Valley, CA that I began treating 5 years ago using fire mimicry. This oak has made significant improvement, as was already documented two years ago here.

The photo sets below are of three coast live oaks, and two coast redwood trees first treated with fire mimicry last year (2017). The first of the series shows a young coast live oak that has lost some leaf density in its canopy. This is an atypical result which may be corrected with further treatments. The other photos sets show an ancient, Native American-era coast live oak that is showing significant improvement in canopy density in just one year. Another mature coast live oak, despite having a major limb removed, is showing slight improvement. And two coast redwood trees are also showing slight improvement in just one year.

Slide1

Slide2 Read the rest of this entry »





Portola Valley oaks respond quickly to fire mimicry

1 03 2018
Slide01.jpg

Culturally-modified, Native American-era oak showing rapid improvement after fire mimicry.

Last February (2017) I treated and photographed 25 coast live oaks in Portola Valley using fire mimicry practices. A couple days ago I revisited the site and re-photographed the oaks to assess their response. The results show noticeable improvements in the density and greenness of the canopies of most of the treated oaks in just one year. This is becoming a common finding in many of the case studies – that the positive response of the oaks to fire mimicry appears to be rapid.

These results are part of a significant body of evidence showing that oaks and other trees can be brought back to health using fairly simple methods that mimic the effects of fire. If you care to learn more about these methods, please enroll in my upcoming course, “Sudden Oak Life: The Science and Practice of Forest Restoration”.

Slide02

Slide03

Slide04 Read the rest of this entry »





Surgical procedure for Sudden Oak Death

22 02 2018

Yesterday I worked on several coast live oak trees on a property here in Big Sur, where  some of the oaks have been infected with a stem canker infection, probably Sudden Oak Death. The incidence of Sudden Oak Death had increased dramatically here in Big Sur, likely a result of the previous (2017) winter’s extreme wetness. In fact, five severely infected oaks were removed from this same property the previous day. The owner has decide on a new course of action and has employed my services, which involve fire mimicry treatments to his oaks. In addition to these treatments, I performed several surgical procedures to remove the stem canker infections. Here are a series of photos from one such procedure.

Surgery prep

Infection prior to surgery, with disinfected tools and tarps to collect infected tissue.

Surgery 1

Removing stem canker infection with axe. Read the rest of this entry »