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Looking for Lichens in Knowland Park

by on November 04, 2013

Xanthoria polycarpa in Knowland Park. Photo: Ken-ichi Ueda
Xanthoria polycarpa in Knowland Park. Photo: Ken-ichi Ueda


aura Baker crouches in the scrub on the northwestern side of Oakland’s Knowland Park. Peering through her hand lens, she examines the branches and burls at the base of a brittle leaf manzanita. Above her a coast live oak—sturdy and gnarled—arches its branches over crowns of the chaparral, forcing the sunlight to filter through in shards.

“How does it feel in here compared to the fire trail?” she asks. “Different?”

Baker has hiked through dry grass to the middle of the thick chaparral, where the summer morning’s gray bluster has faded into quiet warmth. Here, in this microclimate where the roots meet the soil and the morning fog drips through the branches, flourishes one of nature’s smallest communities—lichen.

Laura Baker, a member of the California Native Plant Society (CNPS) East Bay Chapter, is part of a collaborative project with the California Lichen Society to identify and collect lichens in Knowland Park.

“Lichens have not been well understood or heavily studied in the way that plants or animals have,” Baker said. “But people have begun to learn more about them, which means we’re now in a position where conservation can begin to take place.”

The refuge for many of the lichens in Knowland Park is a remnant stand of maritime chaparral atop a ridge that overlooks much of San Francisco Bay, including San Leandro Bay, the outlet for Arroyo Viejo Creek which has its headwaters in Knowland Park.  Fog travels in through the Golden Gate and across the Bay, carrying its moisture up to the ridge of the hills where maritime chaparral occurs.  While interior chaparral is common in California, old-growth maritime chaparral has become increasingly rare, with a dozen small sites in the East Bay that form a 20-mile archipelago along the spine of the hills.  Knowland Park lies at the southern end of the chain but still within reach of the coastal fog.  So, while the highlands of the park are relatively hot and dry, Baker says six coastal species manage to survive among the dozens of lichen species found there.

“It can be dry as heck out there,” Baker says,  “but the dense chaparral canopy tends to dampen winds, trapping humidity.”

Thelomma occidentale. Photo: Ken-ichi Ueda

Thelomma occidentale. Photo: Ken-ichi Ueda

Amid a chamise-thick patch of maritime chaparral, Baker picks up one of the many dead branches blanketing the undergrowth. Many of these branches play host to an array of lichen species. There is the crustose variety that attaches itself to rocks and branches in a thick, bumpy crust. The foliose variety, flat and leafy, with a distinct different underside. And the fruticose variety that grows in tufts of coral-like structures, barely, if at all, clinging to the branches.

Lichens are a composite organism–a symbiotic partnership between algae and fungi–and are considered part of the fungi kingdom. The alga gives lichen its ability to photosynthesize and provides the fungus with a food source, while the fungus gives the lichen most of its physical characteristics, including its thallus structure which protects the single-cell alga. Lichen pigment determines the lichen’s color and shields it from harmful ultraviolet radiation. One species found in Knowland Park, Xanthoria parietina, will appear greenish if growing in the shade and orange when growing in the sunlight.

At a glance, these lichens seem to be no more than a pastel crusting of greens, yellows and grays. Through a hand lens, their microscopic world appears in three-dimensions: Leafy structures nestled upon one another make up the coral-like Physcia callosa, while the gray Thelomma occidental is mottled with black dots, closely resembling potato eyes. Magnified through a dissecting scope, the microscopic and largely unknown world of lichen fauna emerges. While Baker was looking at a lichen sample from Knowland Park a line of peppermint striped mites, less than the size of a pinhead, marched into focus.

“There’s this whole world of tiny invertebrates that are part of the lichen community and form the basis of an elaborate ecosystem,” she says.

Despite their sturdy-looking exteriors, lichen are highly sensitive to changes in air quality and respond to varying levels of nitrogen and sulfur. Some lichen varieties such as the yellow Candelaria thrive in areas with high nitrogen deposition, which often correlates with high levels of air pollution. Conversely, some species of “old man’s beard” struggle in high nitrogen levels and their numbers will diminish in areas of high air pollution. For this reason lichens have been used in science to monitor air quality.

Usnea or 'old man's beard.' Photo: A Bergamin,

Usnea or ‘old man’s beard.’ Photo: A Bergamin,

It is the early fall and after a dry summer, Knowland Park is a yellowed landscape. The native grasses have been chewed to a nub by the goats that graze during the summer, and piles of invasive french broom, removed by volunteers, are lined up across the dirt. But this parched land continues to serve as a refuge for Oakland’s city fringe wildlife, chaparral and lichen that have only ever known Knowland Park as open space.

Baker says she worries that a plan for the Oakland Zoo to annex 56 acres atop the park’s ridgeline could threaten the diverse universe of lichens in the maritime chaparral stands. Should the expansion go ahead, much of the chaparral and its lichen communities, will be fenced within the zoo’s new boundaries, with no guarantee of its conservation.

Outside of the dense chaparral it is warm but windy and across the Bay, Mount Tamalpais is just a bump on the horizon. Back on the fire trail, Baker leads the way to a rocky outcrop encrusted with crustose lichens that will grow on anything from a tree stump to a fence post. They are orange, gray and chartreuse in color and up close, as Baker describes, seem to have somewhat of a bathroom tile pattern. Outside the boundaries of the zoo’s proposed expansion, these lichens will most likely be preserved. But looking down from the rocky hill at the red-stained manzanita chaparral enveloped by that gnarled oak, it is hard to imagine this landscape clouded by a chain link fence.

“All of this is free,” Baker says. “Anyone can come here and get a glimpse of what California once looked like—why would you destroy that?”

Alessandra Bergamin is the Bay Nature Interim Online Editor.

See more articles in: Habitats: Land, Plants and Fungi

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Elise R. Bernstein on November 5th, 2013 at 2:41 pm

Wow! I know that Knowland Park is a very important open and wild space in Oakland, but had no idea of the vital lichen life there. With the threat that much of the Park’s wildlands could be destroyed or fenced off from the public, it is even more important now that we look closely at the wonders of the Park. Just imagine how sad it would be to see those top knolls paved over with a housing development (for animals) built over them. Thank you for waking us up to these treasures of our beautiful Knowland Park. Let us protect those amazing lichens and preserve their sheltering environment as our legacy. See SaveKnowland.org for more info on efforts to protect the park.

Peter Rauch on November 6th, 2013 at 11:07 pm

Knowland Park’s common and rare biodiversity has been perennially abused by the Oakland Zoo’s mismanagement of those natural –and native– resources.

The destructively intensive goat grazing, the one-man mania to destroy ecologically significant sections of Knowland Park, the general public –poorly enlightened about its home-grown natural treasure by the Zoo’s lack of sensitivity to and appreciation for this “freebie” Nature Park, are rapidly leading to the demise of the People’s Treasure Chest –Knowland Park in the wild.

The lichen story is but one of thousands that can be revealed to the Oakland child, parent, grandparent, but the Oakland Zoo will not hear of it. Rather, the Zoo will replace some important jewels with buildings in the Zoo’s own image –a cage showing the wreckage of splendors past.

Shame on the Zoo.

Lech on November 7th, 2013 at 9:12 am

A really written article on lichens, which certainly don’t get enough coverage in the mainstream biological/conservation literature. I’m intrigued by the vegetation associations there at KP and I presume that there are many intriguing lichen to discover. I am especially interested in old man’s beard as an indicator for nitrogen. Does anyone have the reference for this?

Janet on November 7th, 2013 at 10:00 am

California Lichen Society will probably have the reference for atmospheric nitrogen and Usnea (old man’s beard), as that is where I first heard of that lichen’s problem with car smog. I am glad that lichens still grow west of Skyline, but it will take decades, if not centuries, to regrow to the same size if their host vegetation and soil is removed for construction. Ascomycetes rock!

Laura Baker on November 7th, 2013 at 11:46 am

Lech, A good general discussion of nitrogen deposition and its effects on lichens (including the “beard” lichens–Usnea sp.) can be found in “Macrolichens of the Pacific Northwest” by Bruce Mc Cune and Linda Geiser (2009). The authors compare about 170 species of macrolichens (no crustose species) in terms of where they have been detected and the corresponding nitrogen loads found. The species are characterized as oligotrophs (N deposition is <2.5 kg/N/ha/yr), mesotrophs (N deposition is between 2.5 and 4.5 kg/ha/yr) and eutrophs (N deposition is 4.5 to 8 kg/ha/yr). Of the 12 Usnea species listed, all but one (Usnea subfloridana) are categorized as oligotrophs or mesotrophs. See also Geiser, L. H., and P. Neitlich. 2007 "Air pollution and climate gradients in western Oregon and Washington indicated by epiphytic macrolichens." Environmental Pollution 145:203-18. No doubt there are many more recent studies but these were at hand.

Bev Jo on November 9th, 2013 at 12:47 pm

The grasses described are not native. They would be the usual yellow brown European introduced grains that are the real fire hazard in the Bay Area, which is why the goats are helpful. Native grasses are bunch grasses, but there are also rushes and sedges with stay green, and goats should not be allowed to kill them. It’s the invasive grasses that have created so much problem here, more than any of the introduced trees, which we are lucky to have as our native trees are dying.

Bev Jo on November 9th, 2013 at 12:48 pm

Great article about the beautiful lichens! The Usnea is medicinal too….

Laura Baker on November 10th, 2013 at 2:37 pm


Regarding the grasses, there are exemplar quality stands of native grasses (which include both the bunch grasses and some native annual grasses) at Knowland Park, yet another reason that makes this park so special. Of course there are the European non-native grasses that you mention but, both the California Native Plant Society and the California Native Grasslands Association have identified these native stands to be rich enough to be worthy of protection. Unfortunately, the proposed zoo expansion would be located on some of the very best and would destroy them. Regarding the goat grazing: the real problem with the goats is that the Oakland Fire Department has not developed a good management plan which would optimize the grazing and reduce the negative impacts. Instead, the goats are brought in at the wrong time–usually after the non-native grasses have dropped their seeds. The park is also severely overgrazed, way past anything that would reduce fire hazards to acceptable levels and instead the park is grazed down to bare mineral soil which creates a perfect environment for weed invasion and actually favors the non-native grasses over the natives.

Lesley on November 14th, 2013 at 12:06 am

One more thing I would never have known about if it weren’t for a Bay Nature article! I’ve seen lichens for years and casually noticed the differences between them without really thinking about it. I’ll look at them much more carefully now that I know more. And for years I’ve thought of zoos as arks for conservation, but if the Oakland Zoo is wiping out lichens, rare maritime chaparral, and a fine stand of native grasses, what kind of conservation is that?

Martin Klimek on November 18th, 2013 at 6:32 pm

Thank you for a wonderfully informative and well-written piece.

Jean Robertson on November 20th, 2013 at 10:18 am

Nice article about lichens in Knowland Park. That place is such a treasure trove of natural goodies. It’s great to hear more about Lichens in Knowland Park in the press, as this wonderful site is not well know by the general public. (which gives the zoo more chance to ruin this lovely treasure spot, in the name of ‘conservation’–since people may not be aware of how special it is up there) Plus this cooler rainy time is a great time of year to go there. Lots of lots of birds in that park also, it’s a wildlife haven.

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