Lichen on a Napa County oak tree. (Jesse Miller/UC Davis)
Quick Summary
Lichen mostly unaffected by low-severity fires.
In severely burned areas, nearly all lichen were gone, even 16 years after a fire.
As increasingly hot and severe wildfires scorch the West, some lichen communities integral to conifer forests aren't returning, even years after the flames have been extinguished, according to a study from scientists at the University of California, Davis.
Lichen, an often overlooked organism that forms fuzzy, leaflike layers over tree bark and rocks, is an unsung hero in forest ecosystems. It provides food for deer, caribou and elk, and is sometimes the only food source for flying squirrels, which are key prey for threatened spotted owls. Birds and insects use it to eat and nest. An important contributor to the nutrient cycle, it also helps fix nitrogen in forest soils.
“Lichen are beautiful, ecologically important, are all around us and tell us important things about the environment,” said lead author Jesse Miller, a postdoctoral scholar in the Department of Environmental Science and Policy at UC Davis. “But even if you don't notice lichens, you would notice the consequences in ecosystems when they are lost.”
Lace lichen, or Ramalina menziesii, is California's state lichen. These drape across blue oaks in Napa County, which is outside the study area. (Jesse Miller/UC Davis)
Lichen loss and fire severity
For the study, published Aug. 9 in the journal Global Change Biology, researchers sampled lichen communities in about 100 study plots across California's Sierra Nevada region. Five wildfires had burned, at varying levels of severity, in and around the plots between four and 16 years before the study's sampling.
The results show that lichen communities were largely unaffected by low-severity fires. This suggests that prescribed fires and natural wildfires under moderate weather and fuels conditions are compatible with lichen diversity.
But areas that experienced higher severity wildfires had significantly lower abundance and diversity of lichen.
In severely burned areas where most of the trees died, nearly all the lichen were gone, even 16 years after the fire.
This post-fire landscape in the Warner Mountains remains deforested 16 years after the Blue Fire. (Jesse Miller/UC Davis)
Recovery race
The lichens' recovery is likely held back by the loss of tree canopy after the fire, the researchers said. The hot, dry microclimate left in the forest post-fire is not conducive to lichen growth. This indicates that lichen communities burned in Sierra Nevada forests likely won't recolonize until mature trees regrow and the forest canopy is restored. This may exacerbate the effects of climate change that already threaten lichens.
“If the species could keep pace with the rate of climate change, the effects of fire might not be so bad,” Miller said. “But the concern is they might not. These fires happen so quickly and in such a large area, they could cause species ranges to contract faster than they are expanding.”
This lichen community is typical of the study area. The bright chartreuse lichen is wolf lichen (Letharia), which is poisonous and is said to have killed wolves historically in Scandinavia. (Jesse Miller/UC Davis)
The study also indicates that the trend of increasingly dry forests and hotter, bigger and more severe wildfires could cause broad impacts to lichen diversity across the landscape, which could impact nutrient cycling and multiple food-chain interactions among wildlife.
The study areas included:
Yosemite, in areas burned by the Rim (2013) and Grouse (2009) fires
Greater Lake Tahoe Basin, in areas burned by the Showers (2002) and Long (2009) fires
Warner Mountains, in northeastern California, in areas burned by the Blue Fire (2001).
The study's co-authors are Hugh Safford of UC Davis and the USDA Forest Service, Pacific Southwest Region; and Heather Root from Weber State University in Utah.
The research was funded by the USDA Forest Service, Pacific Southwest Region.
Media contact(s)
Jesse Miller, Environmental Science and Policy, jedmiller@ucdavis.edu
Kimberly Hale, UC Davis News and Media Relations, 530-752-9838, klhale@ucdavis.edu
Kat Kerlin, UC Davis News and Media Relations, 530-752-7704, 530-750-9195 (cell), kekerlin@ucdavis.edu, Kerlin will be out of the office Aug 9-13.
Advice for the Home Gardener from the Help Desk of the UC Master Gardener Program of Contra Costa County Client's Request: Hi. We have a beautiful, delicious, amazing plum tree in our backyard. Every year, we've had so many plums that we've been able to share them with friends and neighbors.
This year, our tree produced very few plums. Many were malformed. I also noticed some fungus-looking growth on the tree. Can you help me identify the fungus and/or suggest how I might fix my tree? Thank you! (pics below).
lichen covered trunk
deformed plum
Help Desk Response: Thank you for contacting the UC Master Gardener Program Help Desk about your plum tree. Your email indicates that your plum tree produced fewer plums than usual this year and that some of them are “deformed”. You also have noticed some “fungus looking” growth on the trunk of the tree.
I have what I believe will be welcome news to you (and to your neighbors who no doubt love sharing the fruit from the tree). Based on the information provided in your email and what we can see in the photos you provided, we do believe that the tree has not developed any serious long term problems.
Let me start with the “fungus looking” growth on the tree. What you are seeing are lichens. Lichens are living organisms composed of both a fungus and an algae. The fungus and algae live in a symbiotic relationship. The fungus receives some food from the algae and the algae some food and protection from the fungus. They are not parasitic on the host tree (i.e., they do not receive nourishment from the host) and are generally harmless to the tree. Lichens grow in a wide variety of shapes and colors, ranging from the gray green and yellowish colors shown in your photos to bright red for some types. Lichens are more noticeable on older trees such as your plum than they are on younger trees because the rapidly growing trunks of young trees tends to disburse the lichens. As indicated in this University of California website, it is possible to remove lichens using herbicidal soaps developed specifically to control mosses, lichens, and algae. http://ipm.ucanr.edu/PMG/GARDEN/ENVIRON/lichens.html Since the lichens are not harmful to the tree, using such soaps is unnecessary and we would not recommend it for your tree.
Now let's turn to the question of why your plum tree produced fewer fruits this year than you have had in the past. There are a couple of possible explanations. One possible factor is the weather conditions that we experienced in the spring months when the plum tree was in bloom. This year, we had a warm and generally dry February and early March. Fruit trees tended to bloom early. Then we started having some regular rain storms and cooler weather. The rain storms may have washed off some of the blooms on your plum tree. Cool, rainy weather also tends to keep honey bees and other pollinators away. Those conditions may have held down the fruit set.
Another possibility is “biennial blooming” which often occurs with fruit trees. With biennial blooming, the tree produces a heavy crop one year, a very light crop the following year, followed by a heavy year, then a light year, etc. Hormones produced in fruit seeds are to blame for biennial bearing. The hormones present in the tree with a heavy crop suppress flower-bud formation the following year. In a year with few fruits, hormone levels stay low, so there are more blooms and more fruit the following year. To interrupt this phenomenon, you can reduce the number of fruits that are allowed to develop in a heavy year by thinning the crop.
Possibly for your fruit tree, there might have been a combination effect—the rain removed some of the blooms and held down pollinators and perhaps the tree was already in a lighter fruit production cycle since you had a good crop last summer.
Finally, let me address the “malformation” of some of the fruit. We don't see much evidence of malformed fruit in the photos you sent. We do see one fruit that looks like it has cracked. Such cracking often is a result of erratic watering while the fruit is developing. If the tree received significant water when the ground was dry, it could have taken up the water rapidly and caused the fruit to split.
Possibly the “malformed” fruit has already fallen from the tree so you cannot provide photos. In that case, we would suspect that the pollination was inadequate. Similar to the small crop this year, the rainy conditions and lack of pollinators during bloom could have been factors for the malformed fruit.
We hope that this information is helpful. If you have further questions, you are welcome to contact us again. Enjoy the plums that you do have; hopefully you'll have a better crop next year. tkl Help Desk of the UC Master Gardener Program of Contra Costa County (TKL)
Note: The UC Master Gardeners Program of Contra Costa's Help Desk is available year-round to answer your gardening questions. Except for a few holidays, we're open every week, Monday through Thursday for walk-ins from 9:00 am to Noon at 75 Santa Barbara Road, 2d Floor, Pleasant Hill, CA 94523, although we will be moving late July. We will notify you when that occurs. We can also be reached via telephone: (925) 646-6586, email: ccmg@ucanr.edu, or on the web at http://ccmg.ucanr.edu/Ask_Us/ MGCC Blogs can be found at http://ccmg.ucanr.edu/HortCoCo/ You can also subscribe to the Biog (//ucanr.edu/blogs/CCMGBlog/)