The Grizzly Peak Fire
July 11, 2017
We're making great progress on Scattergrass in the Bay Grove. We will continue there this week. And still, there are tons of Sticky Monkey and Farewell to Spring in bloom, and it's already July.
Also blooming now are the Tarweeds. These are members of the Aster (Sunflower) family that are known for the sticky drops of aromatic oil on their leaves and flower buds. The main Tarweed that is blooming right now along the Skyline Trail is the Coast Tarweed, or Madia sativa. These are tall, rank growers who often colonize open or disturbed areas. They are often the first wave of natives in such areas. They often bloom in the evening. Since Tarweeds usually bloom in the warmer months, this seems to be a successful strategy to protect their flowers from being burnt by the hot sun.
Here is Coast Tarweed in full bloom:
(photo by Bill Bouton, via iNaturalist)
Many people have wondered what is the point of the sticky tar? Up till recently, I have responded, "Imagine you are a small plant trying to flower and make seeds. There are many animals, large and small, who would like to eat you, such as deer and rabbits. What can you do to protect yourself - you can't run away?"
(Credit here to John Muir, who said: "Any fool can cut down a tree. They can't run away.")
So one way plants protect themselves against browsers is to make themselves taste bad by developing strong chemicals. Think about Sage, for example. I believe Tarweeds use this strategy, because I rarely see browse damage to mature plants.
However, some insects have become specialists in eating the flowers of Tarweeds. One of them is the Small Owlet Moth, (Heliothodes diminutiva). The adults lay eggs on Tarweed flower buds and the caterpillars then eat the Tarweed flowers and buds. Here's a picture of the caterpillar.
This picture also clearly shows the many droplets of 'tar' at the tips of the bristles on the bud, stem, and leaves. (Thanks to Ken-ichi Ueda for this picture).
Here is a picture of a caterpillar, caught in the act of eating a Tarweed flower bud:
(photo by Sam Beck)
So how do we Tarweed plants protect ourselves against these hungry ones? What if many other insects are also attracted to Tarweeds and the smaller of them, such as aphids or small flies, can get caught in our sticky tar and can't get away? And, what if predator insects are attracted by the dead ones and come to eat them?
Here is just such a predator, the famous or infamous Spine-Collared Assassin Bug (Pselliopus spinicollis)
The assassin bugs use their long proboscis to spear and inject a a lethal saliva into their prey, which also liquifies the insides of the prey so they can be sucked out. This super clear photo (thanks again, Ken-ichi) is taken of one on an Everlasting flower head. Can you see the spiny collar? The proboscis here is tucked under the body.
And here's one, in action, spearing a fruit fly on a Tarweed:
(photo by Sam Beck)
The assassin bugs are just one of several predator bugs who visit Tarweeds. So the next question is would these predators who come to eat the carrion bugs also notice and eat the caterpillars of the Owlet Moth? And would this reduce the numbers of caterpillars enough to make a difference to the Tarweeds in terms of their fertility - making good seeds?
The answer seems to be yes. This was tested by a couple of researchers at UC Davis, who placed five dead fruit flies on selected tarweed plants each week, and then compared the results with 'un-doctored' control plants. They found that the tarweeds with the extra 'food' had significantly more blossoms and increased seed production. Here's the link to a popular summary of their research:
So, we Tarweeds have adapted to protect ourselves by trapping small insects with our tar, which brings in predator bugs who also eat the caterpillars who are eating our flowers.
That's pretty subtle and complicated, and also just amazing.
Take a closer look next time you are out.
PS. Special thanks to Ken-ichi Ueda of iNaturalist for bringing this drama (and wonderful photos) to our attention.
August 8, 2017
We had some big excitement last week. Because of the Grizzly Peak Fire on Wednesday afternoon, we had to cancel our workday. We did get back to Skyine on Sunday and almost finished with Scattergrass in the Bay Grove. Perhaps one more good session will finish that off.
We'll be out at regular times this week: Wednesday at 4pm and Sunday at 9:30 am. Please let me know if you can make it.
On Wednesday, August 2, the Grizzly Peak Fire burned about 20 acres on the west slope of Grizzly Peak (the peak itself), below the road. The fire site was about a mile north of Siesta Gate. The fire started about 1pm and spread across and upslope for about 4 hours until it was stopped at Grizzly Peak Road. This was on UC property in upper Strawberry Canyon. In several places, the fire jumped over Grizzly Peak Road and started smaller spot fires on the north slope, in Tilden Park territory.
At its peak, over 200 firefighters responded from 9 different local agencies. Calfire brought in crews, 2 fire retardant dropping airplanes, and two helicopters that scooped up water from Lake Anza and dropped it on the fire. No structures were lost, and one firefighter had minor injuries when he uncovered a hornets nest and slipped down a slope. They all did a great job of preventing a larger disaster.
A couple of us visited the fire area on Sunday after our wordkay. To help orient you, here is Cynthia's photo of the fire's aftermath:
This photo looks north from the South Park Drive intersection with Grizzly Peak Blvd. At the top right, you can see the tower atop Grizzly Peak. The main burn area is on the west slope, below the road.
Here is an aerial view of the fire. This is a screenshot I made from KTVU helicopter footage. I believe this is about an hour after the fire started, about 2pm:
This photo is looking east, with Grizzly Peak itself hidden above the smoke plume. The trail at the base is the Frowning Ridge Trail, which zig-zags across this photo. Just above the trail is an ash-colored, burned area. This was mostly Coyote Bush. The burned section above the trail is about 150 feet wide. If you look carefully at the lower center, where the trail goes under trees, you can see a smaller triangular flame area. This small fire section is separate from the main burn and spontaneously ignited about ten minutes into the footage. This is known as 'spotting' - where embers jump from one part of the fire and start new fires. Further up the ridge, the fire has burned under a grove of Monterey Pines and Eucalyptus, and one large tree there is erupting in fire clear up to the crown.
This KTVU footage is still posted on line. It is over an hour long, but the first 15 minutes show the progress of this section of fire as it burns from a small patch above the trail - to across the slope and up under the trees. The footage is fascinating to watch, and here is the link:
Here is a close up photo of the fire from Berkeleyside, as it approached Grizzly Peak Blvd:
As the caption says, this is a Eucalyptus tree in flames. The photo is looking south from the shoulder of Grizzly Peak Blvd.
While some pines and Eucs did fully torch, luckily the fire burned mostly grass and brush under the trees. It never reached the stage of a full 'crown fire' where the fire burns from treetop to treetop and is completely uncontrollable. The Tunnel Fire in 1991 was a huge crown fire that jumped Hwy 24 three times, in hot parched October, with 60 plus mph Diablo winds blowing the fire downhill. Although the weather was warm last week, the wind was manageable, and the trees were still somewhat hydrated from our record rains, it was August and not October, and fire stayed low and small enough to be contained by a massive response.
Here are a couple of close ups of the fire damage. This picture looks uphill from the Frowning Ridge Trail, from the bottom of the helicopter photo:
The fire was hot enough here to completely burn the Coyote Bush and Broom; what you see are just stumps and base branches. Further upslope, you can see the grove of trees that the fire burned through. Some are still quite green and others look very roasted from the heat, but did not fully burn. This area will be just fascinating to revisit in the spring, to see what kinds of plants emerge from dormant seeds.
This picture is from above the tree grove in the previous shot:
Now we are looking west (downhill) along the Frowning Ridge trail. Here you can see two big trees that did completely torch; around the edges you can see Coyote Bushes that roasted from the heat but did not completely burn.
And here is a shot looking west (downhill) along this same ridge from Grizzly Peak Blvd:
In the lower left center, there is a 20 ft. Bay tree, green on top and roasted on the sides. In the mid-center, there's a grove of Live Oaks that got roasted brown, but did not burn. Live Oaks rarely burn from this kind of fire. My prediction is that all the native trees in this shot will leaf out healthy and green in the spring; I've seen this many times. We shall see...
I've included many shots from different angles to show the many faces of one fire. A fire doesn't just burn up everything; it is as particular in its details as any landscape: fire burns everything to the tops in some spots, but right next door just burns the grass and singes the shrubs. It all has to do with placement, fuel, wind, slope, and many particulars.
Botanists tend to love a fire, because the aftermath is so fascinating. Seeds not seen in decades may sprout. In the early days of California botany, when Jepson was at Cal in the early 1900's, he and others found scores of interesting natives on the slopes of Grizzly Peak. Will they return? How will UC manage the burn area (let's hope they do nothing besides remove the Eucs and Pines)?
I have already volunteered to lead a CNPS field trip to the area next April. But please don't wait for that. Gophers are already pushing up fresh mounds of dirt and heat seeking beetles will be laying eggs in the burned trees. Unfolding before us is a new chapter in the ecology of the High Ridge Volcanic Area that extends from Tilden to Sibley. Come see for yourself.