Benefits of Wild Fires
Going to hear naturalist Gary Ferguson speak on wild fires was difficult for me. I have been terrified of fire since I was five-years old when the kindergarten class, seated in a lotus position on wooden folding chairs so feet wouldn’t bang on the seat’s edge, saw a movie about what not to do to prevent fires. After the mother breaks every rule about fire safety, father and children return home to see their home burnt to the ground with only a chimney in sight. The final scene shows them at the hospital. The mother lies on a gurney swathed in gauze with holes cut for her eyes while her children and husband look sorrowfully at her. I did not light a match until I had been smoking for two years, and I worried about every building I entered might burst into flame.
I can’t say I feel any better having heard Ferguson speak at San Diego Horticultural Society’s January meeting, but he did alter my perspective on fire a little.
Trees, Ferguson says, are “the keepers of landscape history.” Fire scars on the rings of a tree show the history of the tree and its site from the tree’s beginnings to when it was cut. Studying a number of trees in a small area can tell scientists the size of past fires, the fires’ directions and the fuel load on the forest floor. The fuel load is the debris of fallen trees and dead branches, dried grasses, and other material that has dried. The ring scars reveal growing conditions in the lifetime of an individual tree, which allows fires to be dated, often to the month in the year the fire occurred. These factors give us a sense of the frequency and intensity of fires, both of which have increased over the past few hundred years. They tell the good and the bad results of fires.
Fires are influential and, in many ways, are beneficial. They determine which species shall survive and what type and shape they may be. Fire releases chemicals and minerals, which filter down to replenish the soil. When the grasses reappear, the nutrients released from the fire create fodder, which is richer in protein. This helps elk and other grazing wildlife to flourish.
Because many seeds only germinate after exposure to the heat of fire, another bi-product of fire is to produce plants which may have not been seen for decades or even centuries. This allows many other animals to benefit from fire.
After a fire many changes occur. One of the first plants to reappear is the fire lily. Within nine days, one species produces carpets of flowers. Meanwhile a burnt forest is still working on rejuvenation. Some conifers only reproduce if their cones become hot enough in a fire to open. They only need 20 seconds of intense heat to kill the tree but that is enough time for cones to open and release their seeds. The new forest will grow unless insects or disease kills the young trees. Surviving trees will grow until another fire causes it to burn reseed once more. Eucalyptus trees have little buds of hormones under their bark. When fire raises their temperature enough, the tree releases these hormones creating new branches on the tree. The roots of mostly burnt aspen and scrub oak will send new shoots of growth after the fire.
In 1910 a season of ferocious wildfires began. From April through August, hundreds of fires broke out. Some fires were set by loggers, campers and steam locomotives. Some came from lightening. The fires in August killed 86 people, destroyed most of Wallace, Idaho, and according to Ferguson’s book, “Land on Fire,” it “destroyed enough timber to fill a freight train more than 2400 miles long.” This fire is called the Big Burn.
As a result of these fires, the Forest Service felt these fires needed to be suppressed. Sixty years later, we paid for suppressing the fires. Fires burn off much of the canopy that shades the forest, which allows protein rich grasses to thrive bringing health and vigor to elk and other animals that browse on. Dried debris, timber, kindling, grasses and other flammable items collected on the forest floor. Eventually, this piled up into enough fuel to turn what should have been an average fire into a much larger and hotter fire. Fire suppression has led to hotter and bigger fires than ever. In his book Ferguson says this suppression means, “A staggering 300 million acres of western forests are today suffering from unnaturally heavy fuel loads.”
Another result is no fires allow diseases and pests to flourish leaving huge quantity of diseased or dead timber for fuel. When there are no healthy large trees to survive, the next forest consists of trees all the same age and species making destruction by pest and disease easier. Shade tolerant white oak has begun to thrive in California. But unlike Ponderosa Pines and other trees which have few or no lower branches, white oak have many lower branches which create a ladder for fire to mount. Ferguson points out that these white oaks have too many knots to make good lumber. In addition, they often climb high enough to burn nearby giant sequoias.
In a future article I will address some topics Ferguson mentioned. How do creatures survive a wild fire? Why are there so many more fires? Why are they so much hotter than they were? And what can we do to prevent them or to survive them?
The March 28 meeting of the Mission Hills Garden Club will take place from 6 to 8 p.m. at the Mission Hills Nursery, located at 1525 Fort Stockton Drive in Mission Hills.
Fire allows this tree to propagate. The cone needs heat to open.
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