Into the Canopy - The 2014 Muir Woods BioBlitz

Stephen Sillett and Marie Antoine climb a redwood tree in Cathedral Grove

Save The Redwoods League

In March 2014 Muir Woods National Monument participated in a BioBlitz to better understand the species living in the canopy at Muir Woods. Scientists Stephen Sillett, Marie Antoine, Cameron Williams and Reese Næsborg were the first to climb trees at Muir Woods. A BioBlitz is an event to find and identify as many species as possible in a short amount of time. The main purpose of a BioBlitz is to get an accurate understanding of the plants, animals, fungi and more in a specific location. The scientists did a biological survey of the canopy, were able to study life in the canopy, and measure a redwood tree and Douglas fir in Muir Woods for the first time.

One of the living things these scientists were particularly interested in finding is lichen. They counted and categorized the different species of lichens in the forest canopy. Lichen is a partnership. It is a symbiotic relationship between different kinds of fungi and algae. Fungi provide the shape and structure. Algae gives lichen its distinct colors. It also provides nutrients for the fungi through photosynthesis. This partnership can exist in many different ways. There are approximately 3,600 known species of lichen in North America. The work of scientists like Sillett, Antonie, Næsborg, and Williams play a role in increasing what we know about lichens.

Dr. Stephen Sillett and botanist Marie Antonie have climbed countless redwood trees in California. They are leading experts in climbing and studying the world's tallest living things. Stephen Sillett always had a fascination with redwoods and other tall trees. Marie Antoine’s first love was lichen. Reese Næsborg also has extensive experience in studying lichens and epiphytes (organisms that grow on the surface of a plant). Cameron Williams has studied forest canopies around the world.

Reese Næsborg and Cameron Williams of UC Berkeley climbing an old-growth Douglas fir.

Tonatiuh Trejo-Cantwell and Save the Redwoods League

The four scientists arrived at Muir Woods on a morning in March in 2014. Cameron Williams and Reese Næsborg wrote about their experience climbing the trees at Muir Woods. Their resulting paper is called What’s in the Trees at Muir Woods? They said, “Since this was the first time trees were climbed for research in Muir Woods, the Park Service was hyper-conscious of the risks. Tree climbing is inherently dangerous without proper training, so the Park was appropriately conservative about permitting this climb. In fact, when we arrived Friday morning the area surrounding the two study trees was fenced off, and safety officers were regulating entry to avoid injury to passersby”. Climbing the world’s tallest trees is no easy job. It should only be attempted with proper equipment, training and experience.

At noon the climbing began. Stephen Sillett and Marie Antoine ascended a 249 foot redwood tree. Cameron Williams and Reese Næsborg climbed a 230 feet tall Douglas fir. Williams and Næsborg wrote, “The study trees were among the largest in the grove, and were probably at least several hundred years old… We began our survey at the top and worked our way down.”

Marie Antoine noticed some interesting qualities of the redwood tree right away. She said, “For the first 50 meters there was nothing growing on the tree {redwood} at all. It was just bare bark.” Williams and Næsborg later described this in their paper. They wrote “This unusual phenomenon is perhaps explainable by the combination of hostile bark chemistry, low light, and relatively dry bark of the coast redwood. Microclimate is particularly suspect here, as this coast redwood stands closely surrounded by other tall trees in the middle of the dense “Cathedral Grove”. The main trunks of coast redwoods generally support relatively sparse epiphyte communities, especially below the crown...”

Coast redwood trees have a chemical called tannic acid. This is what gives redwoods their red color, and it also makes them resistant to fire, insects and disease. This bark chemistry is one factor that makes the redwood truck less hospital to supporting epiphytes.

Stephen Sillett and Marie Antoine climbing Muir Woods redwoods.

Save the Redwoods League

As Marie Antoine continued up the tree, she noticed a change. She said, “Then it was a striking transition at about 50 M. All of the sudden every branch was covered with lichens mostly.” A tall and old tree can have many microclimates. The crown can experience areas that are exposed to lots of sun that will be relatively dry. It can also have areas that are much shadier with more moisture. Large branches can have soil accumulation from decomposing leaves and plant life. This soil becomes a place for ferns, huckleberries and other plants to root. All of these specific microhabitats will provide ideal conditions for a variety of living things. Steve Sillett said of the experience, “We are about 70 M up in a redwood at Muir Woods. And we are doing a survey of all the different things that live on the bark of the tree and we are finding all kinds of stuff. The diversity is fairly high.”

A juvenile arboreal salamander walks on a hand

Save the Redwoods League

The scientists spent hours taking samples, cataloging species and writing meticulous notes. Steve Sillett said, “There was a lot of biodiversity. We found over 40 species of epiphytes on the redwood and they found over 50 species on the Douglas fir.” The two trees were in the same grove. Williams and Næsborg said there is an explanation to why they experienced different kinds of epiphytes in the canopies. They wrote, “These differences in epiphyte species composition are likely due to contrasting substrate and microclimatic conditions between the two trees... The Douglas fir, especially the branches and upper trunk, were so coated with epiphyte biomass that we could hardly see the bark! The main trunk below the crown did not support as much material, but it still had plenty of species. In contrast, the coast redwood was completely devoid of epiphytes below 50 m, with only a couple of moss-covered dead branches at around 50 m, followed by an abrupt transition to lichen-covered branches above 50 m.” The scientists found more than just lichens in the canopy. Williams and Næsborg found a juvenile arboreal salamander about ten meters off the ground in the Douglas fir.

Cameron Williams looks at lichens in an old-growth Douglas fir.

Save the Redwoods League

Steve Sillett was pleasantly surprised by what he found. He said, “The canopy was more vigorous than I expected, I expected with all of this trail and trampling there would be signs of decline, there was none. That was nice. All in all it was a pretty vigorous forest.” The scientists also found that the growth rate of this redwood tree had increased in recent decades. This was an encouraging sign of the health of the forest. Williams and Næsborg wrote, “While this 2014 BioBlitz epiphyte survey included just one coast redwood and one Douglas fir, the survey increased resolution of the epiphyte communities in Muir Woods National Monument, simply for the reason that nobody inventoried canopy epiphytes on large trees there before.”

In November 2014 Reese Næsborg and Cameron Williams came back to Muir Woods. They conducted more expansive research on the different kinds of lichens in the monument. They found a total of 103 species of lichen at Muir Woods. In their article, Lichen Diversity in Muir Woods National Monument, they wrote, “The greatest lichen richness was found on California buckeye, followed by tan oak and Douglas fir, but dead redwood foliage and cones retained by the tree for several years also supported many species.”

Lichens can tell us a lot about the forest ecosystem. Lichens are essential food sources for animals and nest building materials for birds. They can also protect many trees from harsh elements when they coat their bark. Lichens are also indicators of air quality. Some lichens will thrive in poor air quality, while others can not survive unless the air is clean. Studying the lichens in a specific area can give scientists clues on the air quality status. Williams and Næsborg wrote, “The lichen community occupying the forest interior was dominated by species considered either sensitive or somewhat sensitive to air pollution, whereas several pollution tolerant species were discovered in the vicinity of the parking area. However, these pollution tolerant species were not abundant, and pollution sensitive species were also encountered near the parking area.”

Scientists view of the canopy from a Douglas fir

Save the Redwoods League

In 2014 scientists studied the biodiversity and health of the forest. No one had climbed the trees at Muir Woods before. When the scientists traveled up to the canopy of the redwood forest, they were transported to an entirely different habitat. They were surrounded by unique microclimates and species.

Reese Næsborg said of the experience, “We have climbed a lot of trees, but this is absolutely special and a very beautiful place.”