Doug's Mountain Journal
A Chronicle of Natural History on San Bruno Mountain
Doug Allshouse has been writing his seasonal Mountain Journal for many years. We are very pleased to share his reflections on the natural history of the Mountain. Together with David Nelson, he wrote San Bruno Mountain: A Guide to the Flora and Fauna. The book was published by Heyday Books in November 2022 and can be purchased here.
Summer 2024
An overwhelming number of stories for my seasonal journals come from my morning walks. So much so, that I have a photo folder on my desktop titled “Mornings on the Mountain”. I have an eight-minute walk to the Crocker Avenue Gate, which is, by far, the most-used entrance to the Park. It is more accessible to the public than the main entrance on Guadalupe Canyon Parkway, and it is free. Just past the gate there are four interwoven trails: Old Guadalupe, Saddle, Bog, and Day Camp, which offer variable sets of habitats on State-owned land that is managed by the County.
The Saddle is mostly-disturbed grassland that has had over 50 acres of gorse removed over the years. It once supported habitat for the endangered Mission Blue and Callippe Silverspot butterflies, and could do so again with some restoration and reintroduction. It also has disjunct populations of a few plant species found in the Brisbane and South San Francisco areas of the Mountain: Coast Iris, Purple Needle Grass, and California goldenrod. The headwaters of Colma Creek start at the Day Camp and flow gently down to the Bog allowing for water to accumulate in a series of streams and shallow ponds that support moisture-loving plants like sedges, rushes, creek dogwood, tinker’s penny, American speedwell, and two species of willow.
The Complex Beauty of Fog in Fog Forest
The Old Guadalupe Trail and Day Camp Road are embedded within a mostly Monterey cypress and blue-gum eucalyptus forest with a healthy and growing understory of native coast red elderberry and cow parsnip. There also are a few buckeye trees and wax myrtle bushes trying to get established, but it’s still just a lot of cypress and eucalyptus.
We are blessed (or cursed) with summer fog—lots of fog! Unlike the Central Valley and the rest of the country east of the Sierra Nevada, we get coastal fog. It is actually advection fog as compared to Tule fog. Tule fog emanates from the ground, which cools faster than the surrounding air on calm days causing extremely low visibility at ground level. Advection fog is the product of strong northwesterly winds in the summer pushing surface water to the south. Due to the Coriolis Effect, caused by the Earth’s rotation, those waters are pushed eastward toward the coast. Very cold, deep ocean water upwells to replace those warmer waters off the coast, which condenses water vapor into fog. It has a variable floor (bottom) and ceiling (top), which means that it is an airborne river of fog with variable thickness. It is drawn inland by low pressure created by hot air rising upward. Normally at ground levels of a couple of hundred feet above sea level, the fog would cause the sky to look white or light gray while visibility is clear. At higher altitudes, 500 to 1500 feet above sea level, you would be enveloped in the fog and that mimics the effects of Tule fog.
Admittedly, not all fogs are created equal—some are far wetter than others. Blue-gum eucalyptus and Monterey cypress have leaves that are extraordinarily adept at capturing moist fog droplets, condensing them, and raining them to the ground. You can easily hear and see the process. If the fog is high and thick, the background light will be shades of gray creating a strange depth of perception. The trees closest to you will be darker and the trees farther away will be lighter shades of gray. If the fog’s ceiling is not more than a hundred feet or so above you, the morning sun will create an incredibly warm lightshow that is extremely fascinating and stunningly beautiful. So much so, that you forget or don’t even care that you are standing in a mostly non-native forest with the soothing sound of falling raindrops and warm, peaceful sheets of sunlight. Then the cell phone comes out of your pocket and you can’t stop taking photos. Every turn produces a unique view that you don’t want to forget, and before you know it, you have taken thirty photos of the complex beauty of Fog Forest.
[A confession: If I could be like Elizabeth Montgomery (who played Samantha Stephens in the TV series Bewitched, 1964-1972) I would wiggle my nose and turn all the eucalyptus and cypress in Fog Forest into coast live oak and bay trees á la Buckeye and Owl Canyons]
That would be sweet, although I would need to find a home for the leather ferns residing high up in the trees. I have yet to see one on an oak or bay.
Late July and August signals a shift in the landscape. Poison oak responds to those rainless months since the last storm by sucking down the energy of the chlorophyll and turning green leaves to fiery red. Buckeye trees and wild cucumber vines do much the same by dropping leaves or shriveling to brown skeletons with only fruits to show. It’s also time for another favorite plant to appear—pink everlasting. They started appearing in the bog in late August, but I ran into one in lower Buckeye Canyon. On July 29th I was checking out a very tall plant (nearly as tall as me) when I pinched a leaf and smelled it. Hmm—I thought—this smells familiar, but the budding flowers are so large and flashy pink. Could this be? Why yes, it is pink everlasting!! Over many years of observing plants, I have noticed that those in the warmer, drier areas of Brisbane are weeks ahead in development and size as compared to the cooler, wetter areas of the Saddle.
At least five years ago I spied a shelf fungus growing on a eucalyptus at the junction of the Old Guadalupe and Bog trails. I hadn’t seen much of it since, but it made a grand appearance in early August. It’s commonly-known as chicken-of-the-woods or scientifically as Laetiporus sulphureus, a bright and bold polypore fungus. As a polypore fungus (mushroom) it has pores on its underside instead of gills and is edible although the novice should take caution in its preparation. It is a saprophyte, which is an organism that feeds on dead material. So what is a saprophyte doing on a live tree? It is commonly- found on wounds on trees —note the sawn tree limbs— and causes brown rot, which is slowly killing its host. It may be a while since this tree is about sixty-feet tall. This fungus appears quite commonly on eucalyptus as well as oaks and willows.
There is a mating pair of Red-tailed Hawks that have a nest in the pine forest between Panorama School and the Mission Hills development. This is just their second year of rearing offspring. I see these birds year-round and have gotten to know them. On a morning in late July I was heading home on the Old Guadalupe Trail and heard a juvenile Red-tail screaming high up in a eucalyptus above me. A few seconds later I heard another juvenile screaming farther ahead and to the left of me. In an instant, the hawk above me took off and made a beeline away from me and out of my sight. Within a few seconds I saw the other juvenile with an adult circle from my left to my right about 150 feet ahead and the other juvenile had joined them. Then it occurred to me that either mom or dad had taken the kids out for a morning flying lesson. And it made me happy to see the family having fun together.
I’ll be having fun this autumn doing some manzanita hikes and seeing what Mother Nature has in store for the Mountain. Will she dial up some autumn rain in November? Stay tuned, I’ll tell you just after the winter Solstice.
See you on the Mountain…
Doug