Wildfire Effects: Wanted Dead or Alive: Fire Scars and Cavities in Old-Growth Trees

by Jodi Frediani
December 18, 2009

Recent studies by Humboldt State University professor Steve Sillett and others have highlighted the incredible complexity of giant old-growth redwoods: canopies rich with iterated tops, huckleberry gardens, aerial salamanders, and even plankton. Yet only 3-5% of these ancient trees remain along California's coast. While many speak of restoration including creation of old-growth characteristics in young-growth forests, such efforts are new, experimental, and as yet unproven.

Defects (or broken tops, reiterated tops, and cavities) are considered important habitat features in old-growth trees and snags. We know that marbled murrelets rely on large limbs to lay their eggs and raise their chicks. Suitable limbs come with age, and growth can be hastened when tops get broken off. Bats roost in "goose pens" or large hollows, guano littering the cavity floor. Wood rats also take shelter, constructing nests inside large basal hollows. Black bears have been known to take up residence in such trees. Snags are commonly thought to be important to wildlife for nesting, roosting, and foraging, and they are also utilized for courtship display, food caching, perches, and plucking posts. And, of course, downed logs provide a rich ecosystem of their own, one that changes depending on whether the trees fall vertically down slopes, horizontally across them, or they land in or across streams.

A "healthy" cavity

Photo: Jodi Frediani

A variety of factors including slope, wind, and fire can be considered the architects of defect and complexity. A host of species depends on these large trees and their dead counterparts, including all sorts of microfauna and flora, fungi, insects, and invertebrates, as well as salmonids and an assortment of avian and terrestrial mammalian species. Biodiversity flourishes when large old trees are allowed to grow and die in our coastal forests. We are the richer for it.

Basal hollows or interior cavities are formed from a combination of fire and fungal activity. They are usually initiated when hot fires expose the heartwood. Subsequent fires along with fungi cause the core of the tree to decay and hollow out. The size and shape of these cavities vary, some reaching dozens of vertical feet within the interior of the tree, others providing mini-caverns with just a window to the outside. The common factor, however, is that all need fire to initiate the cavity-forming process.
Scientific studies show that the most common ignitions of coast redwood fires were from Native Americans, who burned areas to increase efficiency of food gathering, clear the way for travel, increase food production, and reduce acorn-eating insects. One additional possible motivation would have been to avoid bears or other large mammals hidden in the understory. Fires are commonly set in African landscapes for just this reason. Early ranchers, farmers, and loggers also burned vast tracts during the 19th and 20th centuries. Lightning fires are particularly rare in the coast redwood region due to topography and moisture content--relevant factors typically accompanying lightning strikes.

Firefighters save an old-growth tree in the 2009 Lockheed Fire

Photo: Rick Parfitt

In the past two centuries, old-growth trees have been felled at an alarming rate for their high-quality, dense, tight-ringed lumber. As people moved into the forest, fire began to be perceived as a threat, and Smokey the Bear cautioned us to prevent fires. As fire intervals increased and old growth continued to fall under the chainsaw, cavities became increasingly rare and may soon be relics of a bygone era.

Even with the spate of recent wildland fires in the Santa Cruz Mountains, burning more than 13,000 acres, cavity creation and retention seem to be at risk. In the Summit Fire (2008), at least one large old tree with a basal hollow was labeled a "killer tree" and felled. This stem stood alone upslope of a county road since slash burning in the area (maybe 100 years ago), sporting a large basal cavity on its upslope side. While the latest fire did minimal damage to the tree's integrity, it was suddenly seen as a threat to public safety and was killed, something fire was unable to do.

The felled "killer tree"

Photo: Jodi Frediani

During the 2009 Lockheed Fire, two more old-growth trees were felled for public safety because they were burning near the fire perimeter and there was fear that these trees would push the fire beyond the containment line through the spread of embers. Each was claimed to be worth more than $30,000 as lumber. Two other such trees were saved, when a CalFire Chief determined that climbers could be sent up the trees with hoses to douse the cavity fires. Salvage logging operations are also underway, which will target additional old-growth trees damaged by this fire.

Will we or won't we? Will human concerns continue to take precedence over retention and creation of bio-diverse ecosystems, or will we recognize that such complexity is for the good of us all.

Jodi Frediani became involved in forest and watershed protection in 1980 when 30 acres of old-growth redwoods were proposed for logging adjacent to her spring and fronting a half mile along Majors Creek in Santa Cruz County's Bonny Doon area. Through her efforts, that forest is now protected as state park land, and her spring continues to produce outstanding clean, clear water. Jodi has remained a strong voice for forest and watershed protection, focusing on timber harvest impacts, particularly those affecting old growth and riparian habitat. Jodi's column in FRN focuses on the effects of fire in forested ecosystems.

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Home / Publications / Forest & River News / Winter 2009 /
Wildfire Effects
Wanted Dead or Alive Fire Scars and Cavities in Old-Growth Trees

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Home / Publications / Forest & River News / Winter 2009 / Wildfire Effects Wanted Dead or Alive Fire Scars and Cavities in Old-Growth Trees

Home / Publications / Forest & River News / Winter 2009 /
Wildfire Effects
Wanted Dead or Alive Fire Scars and Cavities in Old-Growth Trees