Category Archives: nature|trees

Rivas Canyon Eucalyptus

What is it? Photography by Gary Valle'.

These shallow channels looked like they might have been cut by a woodworker’s router. But they were cut — or I should say chewed — by Longhorned Borer beetle larvae, feeding on the cambium of a eucalyptus tree.

Fallen eucalyptus in Rivas Canyon. The grooves are from beetle larvae feeding on the cambium of the tree.
Fallen eucalyptus in Rivas Canyon. The grooves are from beetle larvae feeding on the cambium of the tree.

The tree was across the trail in Rivas Canyon. Not unlike the fallen oak on Rocky Peak, Southern California’s multi-year drought likely weakened the eucalyptus, making it susceptible to other pests.

The Rivas Canyon Trail connects Will Rogers State Park to Temescal Canyon. Today (and last weekend) I ran it as part of a long loop from the “End of Reseda” at Marvin Braude Mulholland Gateway Park.

Some related posts: Will Rogers – Temescal Loop, Will Rogers Western Ranch House, Downtown Los Angeles and San Jacinto Peak

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Fallen Oak

A large valley oak along Rocky Peak fire road that toppled following five years of drought.

The valley oak pictured above — one of the larger oaks along Rocky Peak fire road — toppled over in the summer of 2016 following five years of drought.

Fire and drought are a natural part of the valley oak’s habitat and the trees have evolved to withstand ordinary variations in their environment. However, severe fires or extended droughts, or fire in combination with drought can overcome the tree’s defenses.

The drought may have been the culminating factor in the felling of this oak, but fire and other factors may have also played a role.

Base of large valley oak along Rocky Peak fire road that toppled following five years of drought.
Base of large valley oak that toppled following five years of drought. Click for larger image.

According to the Fire Effects Information System (FEIS), the heart-rot fungus Armillaria mellea is usually present in valley oaks and larger oaks tend to be hollow or rotten in the center. The toppled oak was hollow near its base and its interior appears to have been blackened by fire. The FEIS describes instances where the decaying wood in the interior of older valley oaks could ignite in a fire, but leave the exterior bark uncharred.

What fire might have burned the tree? There are two possibilities: the 2008 Sesnon Fire and the 2003 Simi Fire. It probably wasn’t the Sesnon Fire — this photo of the tree, taken about a month after the Sesnon fire, shows little impact. I couldn’t find a photo of the tree following the Simi Fire, but photos taken nearby show a severely burned landscape.

Ultimately, it appears fire and drought weakened the tree, accelerating its heart rot and weakening its roots to the point it could no longer support itself.

Photos of the fallen tree are from this morning’s foggy run along Rocky Peak fire road.

Related post: Chumash Trail – Sesnon & Simi Fires

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Some Fall Color to Bring in the New Year

Some Fall Color to Bring in the New Year. Photography by Gary Valle'.

While much of the country shivers in the cold climes of Winter, the muted colors of the changing season have finally reached the lower elevation areas of Southern California.

Turning leaves of a willow in East Las Virgenes Canyon. December 28, 2017.
Willow in East Las Virgenes Canyon

In this area the leaves of Valley Oaks usually begin to turn around mid-December and the trees lose their leaves around the beginning of the new year. About a month and a half later trees begin to sprout new leaves, usually in mid to late February. From year to year the time frame can vary by as much as 2-3 weeks.

The photo of Valley Oak leaves was taken December 28, 2017 in Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch). This willow in East Las Virgenes Canyon was also showing some nice color.

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Point Reyes Peninsula – A Hidden Island

Running on Kelham Beach, Point Reyes National Seashore

The sand was compact, the breeze cool, the surf up and the running oh so pleasant. Brett and I were running south along Kelham Beach, an idyllic stretch of sand between Point Resistance and Miller’s Point within Point Reyes National Seashore. If the tide was not too high we hoped to reach an area of dramatically folded strata along the 150′ tall sea cliffs.

Our adventure had started with a short run from the Bear Valley Visitor Center to a spot on the San Andreas Fault where a fence was reconstructed to illustrate how the Point Reyes Peninsula lurched 16 feet to the northwest during the 1906 San Francisco earthquake. Fences and roads in the Point Reyes area built across the fault trace were offset by as much as 20 feet during the earthquake.

It is the San Andreas Fault that makes the story of the Point Reyes Peninsula so unusual. A glance at a geologic map shows the rocks of the peninsula to be geologically distinct from those on the other side of the San Andreas. Essentially the Point Reyes Peninsula is an island on the margin of the Pacific Plate that is sitting against the North American Plate. The San Andreas Fault is the boundary between the two plates.

Towering Douglas firs at the junction of the Old Pine Trail and Sky Trail.
Towering Douglas firs at the junction of the Old Pine Trail and Sky Trail.

The core of the Point Reyes Peninsula is a granite similar to a granite found in Southern California. Over many millions of years the chunk of crust was propelled northward along the San Andreas Fault by the movement of the Pacific Plate. The story is not a simple one, involving a combination of faults. At some point — perhaps near current day Point Lobos — the granite core was overlain by the sedimentary rocks we see on the peninsula today.

It seems likely that at times during its 10 million year journey northward from Monterey, the Point Reyes Peninsula may have been separated from the coast. With more than 80% of its perimeter currently bounded by water, it may once again become an island.

Point Resistance and Drakes Bay from the Sky Trail in Point Reyes National Seashore.
Point Resistance and Drakes Bay from the Sky Trail in Point Reyes National Seashore.

After visiting the fault zone we ran across the Point Reyes Peninsula to the coast using the Bear Valley, Mt. Wittenberg, Sky and Coast Trails. For the most part the trails were duff-covered, tree-lined, shaded and cool. For someone that runs mostly in Southern California this was practically nirvana. The previous Saturday I’d run a 50K race on a rocky, exposed course near Los Angeles in 90 degree temps and gusty Santa Ana winds. In the West San Fernando Valley the temperature this year has reached at least 95 °F every month from March through October. In July, August and September the highest temp each month was over 110 °F!

Alders along the Bear Valley Trail in Point Reyes National Seashore.
Alders along the Bear Valley Trail in Point Reyes National Seashore.

It was not 110 °F now. It was about 60 ocean-conditioned degrees. Brett and I had reached the first point where the beach narrowed. There was still room to run, but the beach narrowed even more ahead. We watched as a large wave broke and washed up to the rocks. It looked like the tide was going out, but we weren’t sure. Although the surf wasn’t huge, there was a consistent swell of maybe 6′-8′.

In between sets we took a look around the next corner and it looked sketchy. Debating, we watched as more waves washed up to the base of the cliffs. That part of the exploration would have to wait until another day with a lower tide!

Related post: Point Reyes – Sky Trail Keyhole Loop

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