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 »

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Portola Valley oaks respond quickly to fire mimicry

1 03 2018
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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”.

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Upcoming talk – “The cultural modification of trees and forests by California’s Native Peoples”

4 11 2017
CMT madrone

Culturally modified madrone tree in Big Sur, CA

In January 2018 I will be giving a talk “The cultural modification of trees and forests by California’s Native Peoples“, co-sponsored by the Sempervirens Fund and REI. Details of the talk are here. The talk is free but you will need to sign up through Eventbrite. Hope to see you there!

 





Oaks in Marin respond to fire mimicry

24 03 2017

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On Monday I checked on three coast live oaks trees in Marin County, CA that I’ve been treating with fire mimicry for several years. The first case study (above and below photos) shows the recovery of a large oak after five years of ongoing  fire mimicry treatments. The canopy of this oak is clearly lusher and denser compared to the time of initial treatment.

To remind the reader, fire mimicry treatments are based on traditional forest management practices used by past and present native people in California and elsewhere. The treatments focus on creating habitat and soil conditions favorable for oaks and other native trees.

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(Note that the pine tree behind this oak has since been removed.)

The next case study is a large coast live oak that has received ongoing fire mimicry treatments for three years, as well as several surgical procedures on stem cankers. When I first examined this oak it was severely defoliated and had several small stem cankers (possibly Sudden Oak Death disease) in the trunk. I told the owner that I was not sure the oak could be saved, but he insisted I try. It appears that the owner’s insistence has paid off. The oak has shown a noticeable improvement in canopy lushness and density (see photo sets below). Read the rest of this entry »





Big Sur oaks respond to fire mimcry

13 03 2017

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Three years ago I began fire mimicry treatment on a grove of coast live oaks here in Big Sur. This is an area with serious oak decline problems, with many oaks having stem cankers (probably Sudden Oak Death). My crew and I did significant clearing and pruning of the oaks and fertilized the soils with compost tea and alkaline-rich minerals, and I performed stem canker surgeries on several of the oaks. The owner was adamant that we NOT apply a limewash to the trunks, due to the aesthetics of the white-trunk trees. The oaks were treated again in 2015 with compost tea and soil minerals.

Today I visited the oaks and re-photographed them. Here are the results. While most of the oaks showed a positive response, some did not. My sense is that limewashing the trunks would have given better results. Still, it is useful to see that clearing, pruning, compost tea, and soil minerals, without limewash, can benefit the oaks.

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Forest restoration after the 2015 Valley Fire in Lake County, CA

5 03 2017
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Forest devastation following the Valley Fire in Lake County. Photo taken in October 2015.

In 2015 a devastating wildfire consumed large areas of Lake County, California. Prior to the fires I had been working with some properties affected by the fires and soon afterwards I visited these areas, volunteering my time, to help guide the land managers on how best to manage their lands after the fires. Yesterday I heard back from one of my friends asking about specifics in restoring their forests. My response seems appropriate for a wider audience, so I am posting it here as general informati0n for those who have been affected by wildfires, as well as those who have not . . . Read the rest of this entry »





Diseased oaks flourishing after 12 years

29 11 2016

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Twelve years ago today I initiated fire mimicry treatments on a grove of diseased coast live oaks in Marin County, CA. Since then Leith Carstarphen has been doing the followup work on these trees. Several of these oaks have stem canker infections, probably Sudden Oak Death disease. Two of the oaks in this grove have since died from stem canker infections, but the remainder of the oaks are clearly flourishing.

I should note that, for the above oak, the yellow appearance of the foliage in the recent (right) photo is due to dense clusters of yellowish male flowers.

These thriving oaks stand as testimony to the long-term efficacy of indigenous-based tending techniques (e.g., fire mimicry) in restoring the health of oak forests.

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