From a run at Ahmanson Ranch (now Upper Las Virgenes Canyon Open Space Preserve).

An unusual, offset lightning scar on a Jeffrey pine in the San Gabriel Mountains, near Los Angeles. The tree is located at an elevation of about 8750', on the ridge east of Mt. Hawkins.

The offset scar is not easily explained. Either the scar was offset when created, became offset as the tree aged, or perhaps multiple strikes have somehow created the appearance of an offset. None of these explanations seem completely satisfactory.

The lightning scar on the Mt. Hawkins tree appears to be older than the scar on the Jeffrey pine on the Three Points - Twin Peaks Saddle trail, and quite a bit older than the scar on the Jeffrey pine on Mt. Baldy's North Backbone Trail.

Technorati Tags: lightning

Or did the Curve Fire trigger a lightning strike?

These trees -- on a section of the Pacific Crest Trail east of Windy Gap -- were burned almost six years ago in the 20,857 acre Curve Fire. According to the Curve Fire Burned Area Emergency Report Implementation Plan, the source of ignition for the devastating fire was "a ritual involving the use of fire (candles) and animal sacrifices." The fire started the afternoon of September 1, 2002.

However, in the document An Exercise Involving Flash Flood and Lightning Potential Forecasts, an alternative ignition source was suggested -- an "out of the blue" lightning strike. Forecasters observed a "single positive lightning strike northeast of the Mount Wilson Observatory" about 1:00 PM PDT (2000Z), near the time the Curve Fire started. According to NWS Lightning Safety Outdoors, such bolts from the blue have been documented to travel more than 25 miles from a thunderstorm cloud.

While there is compelling evidence that the blue sky lightning strike occurred, the time of the strike suggests that it was not the initial source of ignition of the Curve Fire. This UCLA Solar Towercam image is time-stamped at 12:58:58, about the time of the strike. It shows the Curve Fire already underway, with a well-developed smoke column. The photograph also shows the cloud development over the San Gabriel Mountains.

An intriguing question comes to mind. Was the lightning strike a coincidence, or was it somehow triggered by the fire, or the smoke?

According to "Forest Fires: Behavior and Ecological Effects" By Edward A. Johnson, Kiyoko Miyanishi (Academic Press, 2001) large scale lightning detection networks have revealed an association between forest fires and the electrification of thunderstorms. Further, "a shift from negative to positive ground flash prevalence in association with fires and forest fire smoke" has been documented.

So it looks like lightning did not start the Curve Fire, but the Curve Fire may have triggered the positive lightning strike observed by the NWS!

The photograph of trees burned in the Curve Fire is from Sunday's Islip Saddle - Mt. Baden-Powell South Fork run.

Technical papers:

CLOUD-TO-GROUND LIGHTNING DOWNWIND OF THE 2002 HAYMAN FOREST FIRE IN COLORADO
Timothy J. Lang* and Steven A. Rutledge
Colorado State University, Fort Collins, Colorado

Enhanced Positive Cloud-to-Ground Lightning in Thunderstorms Ingesting Smoke from Fires
Walter A. Lyons, Thomas E. Nelson, Earle R. Williams, John A. Cramer, and Tommy R. Turner
Science 2 October 1998 282: 77-80 [DOI: 10.1126/science.282.5386.77] (in Reports)

Technorati Tags: lightning, forest fires, San Gabriel Mountains

Incense cedar on the Burkhart Trail in Cooper Canyon. From Sunday's Three Points loop.

Often described as the largest and tallest of the pines, Sugar pine can grow to heights of 150 feet or more. According to the National Register of Big Trees, the current U.S. champion sugar pine measures 209 ft. tall, with a spread of 59 ft.

The sugar pine pictured above is only a fraction of this size -- at first glance it looks like the tree has been topped. Its reduced height is due to the harsh environment in which it grows. Sugar pine and Jeffrey pine found on the higher windswept ridges and mountain tops of the San Gabriel Mountains (and other ranges) are often stunted in this manner.

Research suggests that a number of factors contribute to this adaptation. Foremost among these factors is wind. A tree will respond to a windy environment by increasing the diameter of its trunk, and reducing its height. Water stress is another key factor. Shallow granular soil, low humidity, increased radiation, hot summers and cold winters increase water stress; and a windy environment will amplify the stress.

In such a demanding environment everything matters -- snow deposition patterns, aerodynamic effects, competition with brush, subtle differences in slope aspect, mechanical damage, damage from pests, and more.

The photograph of the sugar pine is from the Pleasant View Ridge Snow run in May.

From Sunday's San Gabriels High Five run and hike.

From Sunday's San Gabriels High Five run and hike.

From a run in Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch).

Technorati Tags: landscape photography

From a run at Upper Las Virgenes Canyon Open Space Preserve (formerly Ahmanson Ranch). Note the hawk in the tree on the left.

Who hasn't pondered the intriguing network formed by the interconnected veins of a leaf? Like many apparently complex self-organized structures, there is a recognizable pattern, but the basis of the pattern is difficult to grasp.

Remarkably, research published in 2002 (S. Bohn et al., Phys. Rev. E, June 2002.) found that there is a simple relationship governing the angles between vein segments in the leaves of dicotyledons, and that this relationship is universal. The study also found that the observed vein angles can be reproduced using a simple force model.

Numerical analysis of leaf scans revealed that the angles between vein segments are directly related to the thickness of the segments. When the vein sizes are similar, the connection appears to form a three-way junction with the angle between the veins about 120 degrees. If the vein sizes are dissimilar, with one much larger than the other, the smaller vein joins the larger at about a 90 degree angle.

The photograph is of a leaf of a Fremont cottonwood (Populus fremontii) along Las Virgenes Creek in Upper Las Virgenes Canyon Open Space Preserve. It was taken on a run from the Victory trailhead on May 16, 2007.

A grizzled guardian of the San Gabriel Mountains, the Wally Waldron Tree stands defiantly astride an airy, rock strewn ridge, just below the summit of 9399 ft. Mt. Baden-Powell.

This is the large incense-cedar (Calocedrus decurrens) mentioned in the post Snowless San Gabriels. It is located on a northeast facing slope near Little Jimmy Spring at an elevation of about 7460' in the San Gabriel Mountains of Southern California. A vertical panorama better shows the size of this tree.

The scar from the 2002 Curve Fire can be seen on the left side of the tree. The black and white cap is about 7 inches wide and suggests a diameter of perhaps 70-80 inches. According to the species information in the FEIS database, in Southern California the largest incense-cedars generally have a diameter at breast height (d.b.h.) of 36-48 inches, but in the Sierra Nevada frequently reach diameters of 84 inches. According to the database, trees over about 200 years old are subject to dry rot, but large trees are often over 500 years old.

Related posts: Pine Mountain Juniper, Heat Wave, Lightning Tree