Alan Stahler: Fire is a tool to reduce rick of high-intensity wildfire
Atom smashers are huge, power-hungry machines. But, truth be told, it’s not hard to bust up atoms — just walk across a rug, and you knock sub-atomic particles, electrons, off atoms.
Those electrons then fly through the air when you reach for the doorknob.
A water molecule is composed of two atoms of hydrogen, doing their best to hold onto their electrons, even as oxygen tries to pull them away. The tug-of-war bonds the hydrogens to the oxygen.
Harnessing the energy of sunlight, trees pull electrons away from a water molecule’s oxygen atom, and return those electrons to the hydrogens, breaking the water molecule apart. They then bond those hydrogens (with their electrons) to molecules of carbon dioxide, building molecules of electron-rich sugar. That sugar is tree-food; it’s also the feedstock to make all the other molecules trees need to build trunks and roots and leaves.
The tree dumps the oxygen from the busted-up water molecule into the atmosphere. But that oxygen is hungry for electrons. So intense is oxygen’s desire for electrons, that, when an atom loses electrons — by whatever means — the atom is said to have been oxidized.
Iron, in the presence of water, oxidizes slowly: Rust.
Fats, exposed to air, oxidize slowly: Rancidity.
Tree trunks and limbs and twigs and leaves oxidize slowly: Rot. Or fast: Fire.
To tell one group of organisms from another, look for “field marks” — characteristics unique to that family, or genus, or species. A field mark for birds, for instance, is feathers.
Many Sierran trees have leaves shaped as needles, but only the pines grow their needles in clusters, each cluster growing out of a small, papery sack — the fascicle — at the base. (Even east-side single-leaf piñons, with just one needle per cluster, have fascicles).
When pines drop their needles, the whole bundle drops, still bound by the fascicle.
Bound together at one end, dropped needles don’t clump tightly together on the ground. The litter at the base of a pine stays loose and airy.
Loose, airy litter burns fast and hot. Fast, hot fires kill trees.
Mature ponderosas self-prune — drop — their lower limbs. Upper branches, well off the ground, are safely out-of-reach of the flames of a ground fire.
Mature ponderosas have thick, dead bark, which insulates the living tree from the fire’s heat.
Mature ponderosas can survive the fast, hot ground fires that kill off their competition. They have even evolved — through their loose, airy litter — to encourage such fires. Ponderosa forests “want” to burn.
Ponderosa forests, before and after the arrival of native Americans, burned often. When Europeans arrived, they described these forests as park-like — large trees, lots of space between, little dead fuel on the ground.
Lumber has knots where branches grew from the trunk. The wood of a self-pruned tree has no knots — a valuable commodity.
As the self-pruned trees of old-growth forests were felled, it became policy to protect the young trees that would replace them by suppressing fire. Decades of dead wood, that would have burned off a little at a time, has now built up. The problem has been magnified by drought.
Frequent, low-intensity fire is a tool — one of the first to be employed by humans, employed even by trees — that reduces the risk of high-intensity wildfire.
Al Stahler teaches nature classes for students of all ages, kid to adult. His science programs can be heard on KVMR-FM, and he may be reached at email@example.com
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