rock-fields, lake-shores, meadows, and other natural fire-resisting
boundary lines between forests are beginning to be used and can be
more fully utilized for fire-lines, fire-fighting, and fire-defying
places. These natural fire-barriers may be connected by barren cleared
lanes through the forest, so that a fire-break will isolate or run
entirely around any natural division of forest. With such a barrier a
fire could be kept within a given section or shut out of it.
In order to fight fire in a forest it must be made accessible by means
of roads and trails; these should run on or alongside the fire-barrier
so as to facilitate the movements of fire patrols or fire-fighters.
There should be with every forest an organized force of men who are
eternally vigilant to prevent or to fight forest fires. Fires should
be fought while young and small, before they are beyond control.
There should be crows'-nests on commanding crags and in each of these
should be a lookout to watch constantly for starting fires or
suspicious smoke in the surrounding sea of forest. The lookout should
have telephonic connection with rangers down the slopes. In our
national forests incidents like the following are beginning to occur:
Upon a summit is stationed a ranger who has two hundred thousand acres
of forest to patrol with his eyes. One morning a smudgy spot appears
upon the purple forest sea about fifteen miles to the northwest. The
lookout gazes for a moment through his glass and, although not certain
as to what it is, decides to get the distance with the range-finder.
At that instant, however, the wind acts upon the smudge and shows that
a fire exists and reveals its position. A ranger, through a telephone
at the forks of the trail below, hears from the heights, "Small fire
one mile south of Mirror Lake, between Spruce Fork and Bear Pass
Trail, close to O'Brien's Spring." In less than an hour a ranger leaps
from his panting pony and with shovel and axe hastily digs a narrow
trench through the vegetable mould in a circle around the fire. Then a
few shovelfuls of sand go upon the liveliest blaze and the fire is
under control. As soon as there lives a good, sympathetic public
sentiment concerning the forest, it will be comparatively easy to
prevent most forest fires from starting and to extinguish those that
do start.
With the snow over, I started for the scene of the first fire, and on
the way noticed how much more rapidly the snow melted in the open than
in a forest. The autumn sun was warm, and at the end of the first day
most of the snow in open or fireswept places was gone, though on the
forest floor the slushy, compacted snow still retained the greater
portion of its original moisture. On the flame-cleared slopes there
was heavy erosion; the fire had destroyed the root-anchorage of the
surface and consumed the trash that would ordinarily have absorbed
and delayed the water running off; but this, unchecked, had carried
off with it tons of earthy material. One slope on the first burn
suffered heavily; a part of this day's "wash" was deposited in a
beaver pond, of half an acre, which was filled to the depth of three
feet. The beavers, finding their subterranean exits filled with wash,
had escaped by tearing a hole in the top of their house.
Leaving this place, I walked across the range to look at a fire that
was burning beyond the bounds of the snowfall. It was in a heavily
forested cove and was rapidly undoing the constructive work of
centuries. This cove was a horseshoe-shaped one and apparently would
hold the fire within its rocky ridges. While following along one of
these ridges, I came to a narrow, tree-dotted pass, the only break in
the confining rocky barrier. As I looked at the fire down in the cove,
it was plain that with a high wind the fire would storm this pass and
break into a heavily forested alpine realm beyond. In one day two men
with axes could have made this pass impregnable to the assaults of any
fire, no matter how swift the wind ally; but men were not then
defending our forests and an ill wind was blowing.
Many factors help to determine the speed of these fires, and a number
of observations showed that under average conditions a fire burned
down a slope at about one mile an hour; on the level it traveled from
two to eight miles an hour, while up a slope it made from eight to
twelve. For short distances fires occasionally roared along at a speed
of fifty or sixty miles an hour and made a terrible gale of flames.
I hurried up into the alpine realm and after half an hour scaled a
promontory and looked back to the pass. A great cloud of smoke was
streaming up just beyond and after a minute tattered sheets of flame
were shooting high above it. Presently a tornado of smoke and flame
surged into the pass and for some seconds nothing could be seen. As
this cleared, a succession of tongues and sheets of flame tried to
reach over into the forest on the other side of the pass, but finally
gave it up. Just as I was beginning to feel that the forest around me
was safe, a smoke-column arose among the trees by the pass. Probably
during the first assault of the flames a fiery dart had been hurled
across the pass.
Up the shallow forested valley below me came the flames, an inverted
Niagara of red and yellow, with flying spray of black. It sent forward
a succession of short-lived whirlwinds that went to pieces
explosively, hurling sparks and blazing bark far and high. During one
of its wilder displays the fire rolled forward, an enormous horizontal
whirl of flame, and then, with thunder and roar, the molten flames
swept upward into a wall of fire; this tore to pieces, collapsed, and
fell forward in fiery disappearing clouds. With amazing quickness the
splendid hanging garden on the terraced heights was crushed and
blackened. By my promontory went this magnificent zigzag surging front
of flame, blowing the heavens full of sparks and smoke and flinging
enormous fiery rockets. Swift and slow, loud and low, swelling and
vanishing, it sang its eloquent death song.
A heavy stratum of tarlike smoke formed above the fire as it toned
down. Presently this black stratum was uplifted near the centre and
then pierced with a stupendous geyser of yellow flame, which reddened
as it fused and tore through the tarry smoke and then gushed
astonishingly high above.
A year or two prior to the fire a snow slide from the heights had
smashed down into the forest. More than ten thousand trees were mowed,
raked, and piled in one mountainous mass of wreckage upon some crags
and in a narrow-throated gulch between them. This wood-pile made the
geyser flames and a bonfire to startle even the giants. While I was
trying to account for this extraordinary display, there came a series
of explosions in rapid succession, ending in a violent crashing one.
An ominous, elemental silence followed. All alone I had enjoyed the
surprises, the threatening uncertainties, and the dangerous
experiences that swiftly came with the fire-line battles of this long,
smoky war; but when those awful explosions came I for a time wished
that some one were with me. Had there been, I should have turned and
asked, while getting a better grip on my nerves, "What on earth is
that?" While the startled mountain-walls were still shuddering with
the shock, an enormous agitated column of steam shot several hundred
feet upward where the fiery geyser had flamed. Unable to account for
these strange demonstrations, I early made my way through heat and
smoke to the big bonfire. In the bottom of the gulch, beneath the
bonfire, flowed a small stream; just above the bonfire this stream had
been temporarily dammed by fire wreckage. On being released, the
accumulated waters thus gathered had rushed down upon the red-hot
rocks and cliffs and produced these explosions.
In the morning light this hanging terraced garden of yesterday's
forest glory was a stupendous charcoal drawing of desolation.
Insects in the Forest
Insects in the Forest
The big trees of California are never attacked by insects. This
immunity is extraordinary and may be the chief characteristic that
enables these noble trees to live so long. Unfortunately it is not
shared by other species. The American forests are infested with
thousands of species of injurious and destructive insects. These
insects, like the forest fires, annually kill numerous forest areas,
and in addition leave millions of deformed and sickly trees scattered
through the living forest to impair and imperil it. After some general
tree studies which have occupied odd times for years and extended
through the groves and forests of every State and Territory in the
Union, the conclusion has been forced upon me that the forests are
more widely wasted by insects than by fire.
Some of Nature's strange ways are exhibited in the interrelation of
insects and fires in tree-killing. It is common for the attack of one
of these tree-enemies to open the way for the depredations of the
other. The trees that insects kill quickly become dry and inflammable
and ready kindling for the forest fire. On the other hand, the
injuries that green trees often receive from forest fires render them
most susceptible to the attacks of insects.
This interrelation--almost coöperation--between these arch-enemies of
the forest was impressed upon me during my early tree studies. One day
I enjoyed a splendid forest sea from the summit of a granite crag that
pierced this purple expanse. Near the crag a few clumps of trees stood
out conspicuous in robes of sear yellow brown. Unable to account for
this coloring of their needles, I went down and looked them over. The
trees had recently been killed by insects. They were Western yellow
pine, and their needles, changed to greenish yellow, still clung to
them. In each clump of these pines there were several stunted or
deformed trees, or trees that showed a recent injury. The stunted and
injured trees in these clumps were attacked and killed by beetles the
summer before my visit. In these injured trees the beetles had
multiplied, and they emerged the following summer and made a deadly
attack upon the surrounding vigorous trees. Although this latter
attack was made only a month or two before my arrival, the trees were
already dead and their needles had changed to a sickly greenish
yellow. Amid one of these clumps was a veteran yellow pine that
lightning had injured a few years before. Beetles attacked and killed
this old pine about a year before I appeared upon the scene. It was
the only tree in this now dead clump that was attacked on that first
occasion; but some weeks before my visit the beetles in multiplied
numbers swarmed forth from it and speedily killed the sound
neighboring trees.
These conclusions were gathered from the condition of the trees
themselves together with a knowledge of beetle habits. Not a beetle
could be found in the lightning-injured pine, and its needles were dry
and yellow. The near-by dead pines were full of beetles and their
eggs; the needles, of a greenish yellow, were slightly tough and still
contained a little sap.
While I was in camp one evening, in the midst of these tree studies,
the veteran pine, now dead, was again struck by lightning. As
everything was drenched with rain, there appeared to be no likelihood
of fire. However, the following morning the old pine was ablaze. In
extinguishing the fire I found that it had started at the base of the
tree at a point where the bolt had descended and entered the earth. At
this place there was an accumulation of bark-bits from the trunk,
together with fallen twigs and needles from the dead tree-top. Thus a
dead, inflammable tree in the woods is kindling which at any moment
may become a torch and set fire to the surrounding green forest.
Although fires frequently sweep through and destroy a green forest,
they commonly have their start among dead trees or trash.
The pine beetle just mentioned attacks and burrows into trees for the
purpose of laying its eggs therein. When few in number they confine
their attacks to trees of low vitality,--those that will easily
succumb to their attack. The speedy death of the tree and the
resultant chemical change in its sap appear to be necessary for the
well-being of the deposited eggs or the youngsters that emerge from
them. When these beetles are numerous they freely attack and easily
kill the most vigorous of trees.
The pine beetle is one of a dozen species of bark beetles that are
grouped under a name that means "killer of trees." Each year they kill
many acres of forest, and almost every year some one depredation
extends over several thousand acres. The way of each species is
similar to that of the others. The beetles of each species vary in
length from a tenth to a fifth of an inch. They migrate in midsummer,
at the time of the principal attack. Swarming over the tree, they at
once bore into and through the bark. Here short transverse or vertical
galleries are run, and in these the eggs are laid.
In a short time the eggs hatch into grubs, and these at once start to
feed upon the inner bark at right angles to the galleries, extending
to right and left around the tree. It does not require many of them to
girdle the tree. Commonly the tree is dead in two months or less. All
these little animals remain in the tree until late spring or early
summer, when they emerge in multiplied swarms and repeat the deadly
work in other trees.
The depredations of these insects are enormous. During the early
eighties the Southern pine beetle ruined several thousand acres of
pines in Texas. Ten years later, 1890-92, it swarmed through western
North Carolina, Virginia, and West Virginia to southern Pennsylvania
and over an area aggregating seventy-five thousand square miles, and
killed pines of all species and ages, leaving but few alive. Within
the past few years the mountain and Western pine beetles have ruined a
one-hundred-thousand-acre lodge-pole pine tract in northeastern
Oregon, destroying not less than ninety per cent of the stand. During
the past decade the Black Hills beetle has been active over the Rocky
Mountains, where in some districts it has destroyed from ten to eighty
per cent of the Western yellow pines. In the Black Hills the forests
over several thousand square miles are ruined.
These bug-killed trees deteriorate rapidly. In most cases a
beetle-killed pine is pretty well rotted in five years and usually
falls to pieces in less than a decade. Borers attack upon the heels of
the beetles, and the holes made by the beetles admit water and fungi
into the wood. This rapidly reduces the wood to a punky, rotten mass.
One day in Colorado I tore a number of wind-wrecked, bug-killed trees
to pieces and was busily engaged examining the numerous population of
grubs and borers, when some robins and other birds discovered the
feast, collected, and impatiently awaited their turn. Perceiving the
situation, I dragged a fragment of a log to one side for examination
while the birds assembled to banquet and dispute.
Returning to the rotten logs for another grub-filled fragment, I
paused to watch some wasps that, like the birds, were feasting upon
these grubs. A wasp on finding a grub simply thrust his snout into the
grub and then braced himself firmly as he bored down and proceeded to
suck his victim's fluids. In throwing a log to one side I disturbed a
bevy of slender banqueters that I had not seen. Instantly a number of
wasps were effervescing round my head. Despite busy arms, they
effectively peppered my face, and I fled to a neighboring brook to
bathe my wounds.
While I was at a safe distance, cogitating as to the wisdom of
returning for further examination of the logs, a black bear appeared
down the opening. From his actions I realized that he had scented not
myself but the feast in the log-pile. After sniffling, pointing, and
tip-toeing, he lumbered toward the logs. Of course I was curious as to
the manner of his reception and allowed him to go unwarned to the
feast. Two Rocky Mountain jays gave a low, indifferent call on his
approach, but the other birds ignored his coming. With his fore paw he
tore a log apart and deftly picked up a number of grubs. All went well
until he climbed upon the pile of wreckage and rolled a broken log off
the top. This disturbed another wasp feast. Suddenly he grabbed his
nose with both fore paws and tumbled off the pile. For a few seconds
he was slapping and battling at a lively pace; then, with a
_woof-f-f-f!_ he fled--straight at me. I made a tangential move.
The hardwoods are also warred upon by bugs, weevils, borers, and
fungi. The percentage of swift deaths, however, that the insects cause
among the hardwoods is much smaller than that among the pines; but the
percentage of diseased and slow-dying hardwoods is much greater. The
methods of beetles that attack oaks, hickories, aspens, and birches
are similar to the methods of those that attack pines and spruces.
They attack in swarms, bore through the bark, and deposit their eggs
either in the inner bark or in the cambium,--the vitals of the tree.
The grubs, on hatching, begin to feed upon the tree's vitals. In this
feeding each grub commonly drives a minute tunnel from one to several
inches in length. Where scores of grubs hatch side by side they drive
a score of closely parallel tunnels. Commonly these are either
horizontal or vertical and generally they are numerous enough to make
many complete girdles around the tree. Girdling means cutting off the
circulation, and this produces quick death.
While these beetles are busy killing unnumbered millions of trees
annually, the various species of another group of beetles known as
weevils are active in deforming and injuring even a greater number.
They mutilate and deform trees by the millions. The work of the
white-pine weevil is particularly devilish. It deposits its eggs in
the vigorous shoots of the white-pine sapling. The eggs hatch, and the
grubs feed upon and kill the shoot. Another shoot bursts forth to take
the place of the one killed; this is attacked and either killed or
injured. The result is a stunted, crooked, and much-forked tree.
Borers attack trees both old and young of many species, and a few of
these species with wholesale deadly effect. Birches by the million
annually fall a prey to these tree-tunnelers, and their deadly work
has almost wiped the black locust out of existence. Borers pierce and
honeycomb the tree-trunk. If their work is not fatal, it is speedily
extended and made so by the fungi and rot that its holes admit into
the tree.
Trees, like people, often entertain a number of troubles at once and
have misfortunes in series. A seedling injured by one insect is more
likely to be attacked again, and by some other insect, than is the
sound seedling by its side. Let a seedling be injured, and relays of
insects--often several species at a time and each species with a way
of its own--will attack it through the seedling, sapling, pole, tree,
and veteran stages of its growth until it succumbs. Or let a vigorous
tree meet with an accident, and like an injured deer it becomes food
for an enemy. If lightning, wind, or sleet split the bark or break a
limb, through these wounds some spore or borer will speedily reach the
tree's vitals. In many cases the deadly work of parasitic plants and
fungi is interrelated with, and almost inseparable from, the
destructive operations of predacious insects. Many so-called tree
diseases are but the spread of rot and fungi through the wood by means
of an entrance bored by a borer, weevil, or beetle.
The bark of a tree, like the skin on one's body, is an impervious,
elastic armor that protects blood and tissues from the poisonous or
corrupting touch or seizure of thousands of deadly and incessantly
clamoring germs. Tear the skin on one's body or the bark upon a tree,
and eternally vigilant microbes at once sow the wound with the seeds
of destruction or decay. A single thoughtless stroke of an axe in the
bark of a tree may admit germs that will produce a kind of
blood-poisoning and cause slow death.
The false-tinder fungus apparently can spread and do damage only as it
is admitted into the tree through insect-holes or the wounds of
accidents. Yet its annual damage is almost beyond computation. This
rot is widely distributed and affects a large number of species. As
with insects, its outbreaks often occur and extend over wide areas
upon which its depredations are almost complete. As almost all trees
are susceptible to this punk-producer, it will not be easy to
suppress.
[Illustration: A TREE KILLED BY MISTLETOE AND BEETLES]
The study of forest insects has not progressed far enough to enable
one to make more than a rough approximation of the number of the
important species that attack our common trees. However, more than
five hundred species are known to afflict the sturdy oak, while four
hundred prey upon the bending willow. The birches supply food to about
three hundred of these predacious fellows, while poplars feed and
shelter almost as many. The pines and spruces are compelled
permanently to pension or provide for about three hundred families of
sucking, chewing parasites.
The recent ravages of the chestnut-tree blight and the appalling
depredations of the gypsy and brown-tailed moths, together with other
evils, suggest at once the bigness of these problems and the
importance of their study and solution. The insect army is as
innumerable as the leaves in the forest. This army occupies points of
vantage in every part of the tree zone, has an insatiable appetite, is
eternally vigilant for invasion, and is eager to multiply. It
maintains incessant warfare against the forest, and every tree that
matures must run a gantlet of enemies in series, each species of which
is armed with weapons long specialized for the tree's destruction.
Some trees escape unscarred, though countless numbers are killed and
multitudes maimed, which for a time live almost useless lives, ever
ready to spread insects and disease among the healthy trees.
Every part of the tree suffers; even its roots are cut to pieces and
consumed. Caterpillars, grubs, and beetles specialize on defoliation
and feed upon the leaves, the lungs of the trees. The partial
defoliation of the tree is devitalizing, and the loss of all its
leaves commonly kills it. Not only is the tree itself attacked but
also its efforts toward reproduction. The dainty bloom is food for a
number of insect beasts, while the seed is fed upon and made an
egg-depository by other enemies. Weevils, blight, gall, ants, aphids,
and lice prey upon it. The seed drops upon the earth into another army
that is hungry and waiting to devour it. The moment it sprouts it is
gnawed, stung, bitten, and bored by ever-active fiends.
Many forest trees are scarred in the base by ground fires. These trees
are entered by insects through the scars and become sources of rot and
insect infection. Although these trees may for a time live on, it is
with a rotten heart or as a mere hollow shell. A forest fire that
sweeps raging through the tree-tops has a very different effect: the
twigs and bark are burned off and the pitches are boiled through the
exterior of the trunk and the wood fortified against all sources of
decay. This preservative treatment often gives long endurance to
fire-killed timber, especially when the trees killed are yellow pine
or Douglas spruce. Many a night in the Rocky Mountains my eager,
blazing camp-fire was burning timber that forest fires had killed
forty and even sixty years before.