Nature Notes From Crater Lake
Volume 6, No. 4, September 1933
Wizard Island: It's Succession of
Life
By Dr. Wm. G. Vinal, Ranger-Naturalist
Wizard Island is never the same twice.
As the same moment no two people see it the same and it is only by
continuous observation and accretion of ideas that the complete story of
its origin and life can be unfolded.
It is evident to an observer on the
Watchman, Hillman Peak or Llao Rock, looking down on the island, that it
is made up of the three zones of volcanic contributions, namely blocks
of rough andesitic lava at the base along the shore line, a coarse
undulating lava flow along the intermediate slopes and the symmetrical
conical slopes of ash and cinders above. Disintegration and
decomposition have not contributed much to the breaking down of these
lava slopes. The volcano is so young geologically that very little
progress has been made in converting the raw slaggy slopes into a soil
with humus. A slight covering of volcanic dust co-mingled with organic
material has filled the more gentle slopes and irregular crevices as the
base. It is evident that there is not sufficient soil nor is the
humidity sufficient to invite the growth of such shade plants as the
coral root, trailing raspberry and a host of other deep wood plants.
Darwin's classical earthworms have not
arrived nor could they find any subsoil to bring up to the surface. The
plants on Wizard Island, therefore, are limited to those forms whose
structure allows them to suffer drought.
The stages in the vegetal conquest of
Wizard Island may be the key to the many successive revegetations of the
slopes of Mt. Mazama. What were the first plants to land and how did
they come? After the last swirling flow of lava and the vanishing of
steam there were, as always before, prevailing westerlies wafting spores
of lichens, fungi, and eric mosses and perhaps the winged seeds of
conifers from the Rim. The water currents undoubtedly floated seeds.
Probably 99% of these germs of life were born for naught as is the great
mass of pollen that washes to and fro today. Many would-be colonizers
were destined to land on such barren, sterile places that they were
inevitably doomed to perish.
The only plants today that are
succeeding in the glare of light on the lower rock blocks are the
lichens. The golden lichen is a crustose form which can stand a certain
amount of direct sun but must have shade a part of the day. The gray
lichens could also have been early arrivals. It must have been eons
before any crannied wall accumulated dust particles enough to encourage
a moss plant. The lace fern (Chelianthes gracilliam) grows in
pockets on the lower rock ledges, Woodsie (Woodsia oregana) pokes
its rusty fronds from protected spots on the rocky summit, and the rock
brake (Cryptogramma acrtostichoides) is found in rock clefts in
the crater. Those are the only members of the fern tribe that have
succeeded in mastering the situation. Untold ages had to follow before
seed plants could anchor long enough to send their rootlets down to the
water table.
In the meantime what could have been
going on in the way of seed arrivals on the ash pile above the cone? It
is a mile from the west rim across Skell Channel to the crater of Wizard
Island. It must have been a strong west wind that enabled the first
mono-planed seeds of the conifers and the ballooms of the composites and
figworts to flutter from the rim of Crater Lake to the sides of the
island cone. There had to be at least one from each conifer, the
mountain hemlock (Tsuga mertensiana), the white bark pine (Pinus
albicaulis), the western white pine (Pinus monticola), the
lodgepole pine (Pinus contorta), and the shasta red fir (Abies
magnifica shastensis).
It may not be sheer accident that the greatest growth of evergreens is
on the west side of the island, that the largest and possibly oldest
western white pines and Shasta red firs are at least five hundred feet
above the lake, or that the best stand (of) lodgepole and white bark
pine is at the summit. In other words, did not the colonizers come by
the air route and land as they would, hit or miss, but mostly miss? The
seeds successful in growing. The ash cone proved to be the best of the
three areas. It was these veterans that lived to perpetuate each its own
kind. They remained to shake their seeds downward that the forest might
grow upward to eventually cover the cone.
The five conifers had a most difficult
time in establishing themselves. The remarkably few evergreen seedlings
on the ash slope are mute testimony to the fate of most seeds which are
unfortunate enough to cast their lot on such a dry, sterile environment.
Those which succeeded in reaching a goodly size still had to fight.
About 500 feet up the cone lava rocks from a fissure flow have imbedded
themselves eighteen inches above the slope in the trunk of a Shasta red
fir and at a still higher altitude a lava rock as large as a man's head
has become wedged between the upright trunks of a white bark pine. Such
land slides are denuding agents for seedlings and surely handicaps to
veteran tree. In one of the larger gullies the larger trees have had
their heads snapped off about twenty feet above ground. The fact that
they held fast with their root systems indicates a deep root system, or
that they were broken by a wind storm which whirled up the valley when
the trees were braced by deep snow. Many a wind-blown tree has lost its
main trunk to start again. The battle is with the elements and not with
each other.
And what of the antecedent herbs? The
shade-requiring plants of the deep forest are few indeed. The
small-leaved penstemon, the pine-mat manzanita and the wintergreens
represented by the one-sided pyrola, the toothed wintergreen and
pipsissewa are practically the only arrivals. The representatives of the
open woods are the white hawkweed and the elephant's head. The few herb
and shrubs of the forest indicate that the stand must be young in its
development.
The colonizers of the ash slope are the
strong-stemmed, creeping perennials that are able to battle alone. The
amount of heat on the slope is much greater than on the wooded plateau
below. Any plant growing there must be drought resistant, capable of
anchoring tightly, and able to stand punishment when bombarded by
pumicite or when buried alive by miniature sand dunes. Theirs is a
terrific punishment. The typical plants of this area are arenaria,
chalice cup, white buckwheat, and Newberry's knotweed. All of these
hardy pioneers send runners into the bare ash and are often exposed by
the drift of the soil. Their offshoots, rhizomes, or stolons are
controlled by gravity and swing like cables down the slope. This may be
thought of as a linear migration (as opposed to radial migration) and
new plants spring up just below the parent plant. As many as eight
successive offspring were counted on one cable which had been sent out
by white buckwheat (Eriogonum ovalifolium).
Interspersed with the "cable" growths
are such hoary and stemless plants as the silver leafed senecio, and
sulphur flower, and the root-storing carrot (Cogswellia martindalei).
In protected spots the fireweed, Englemann's aster, the alpine, false
dandelion, arnica, and wood rush have made appearance and stand ready to
furnish the strands of crosswise vegetation as soon as the "cable"
plants get stabilized. The vegetation on the ash lope has hardly reached
the stage of being able to weave a mat or turf.
A third zone of herbaceous plants
appears near the top of the island. Although the island does not reach
into alpine heights it has a few plants which are typically montane in
character. At the crater a few yellow mountain daisies (Hulsea nana)
grow just outside the rim on the south side in loose red cinders. A few
feet across the crest, but within the crater and on the north facing
slope, is the heart-leafed arnica (Arnica cordifolia) and the
more widely spread alpine saxifrage (Saxifraga tolmei). This
little saxifrage starts as a tuft in back of a rock and in due time
forms a dense mat. The silver-leafed senecio (Raillardella argentea)
grows on the dry ash of the north slope outside the cone and penstemons
adorn the inner slope. While in the "cable" plant district it is largely
ability to adapt to a small amount of moisture and shifting soils around
the crater it is a matter of little moisture and direct or indirect
sunlight.
The trees are herbaceous plants listed
are those whose seeds could have been brought by the wind. The shrub
plants with berried fruits also came by the air route except that they
borrowed their wings. Only two shrubs of red berried elder (Sambucus
racemosa) were noted on the cone. One was at an altitude of 6650
feet and the other at the bottom of the crater. Four little offspring
are growing near the base of the crater specimen. A solitary gooseberry
bush was found at an altitude of 6250 feet in the forest. The scattered
appearance of the many-stemmed mountain ash (Sorbus sitchensis)
with its berry-like apple, the pine-mat manzanita, and the mazama
currant have all appeared above the encroaching forest. The pine
mistletoe (Arcenthobium) could well have taken the bird express
to the white bark and lodgepole pines on the rim of the crater.
The pine mistletoe could not arrive
before its host. The same is true of parasitic paint brushes. The aphids
in the rolled red-leaves of manzanita had to wait for the hosts'
arrival. The tiny craters of the "doodlebugs" (Ant Lions) found at such
widely separated stations as the first trees above shoreline (6207
feet), the upper limit of the shady forest (6437 feet), the fissure flow
at 6610 feet in altitude and the top of the rim (6940 feet) show that
such barriers as Skell Channel, bare lava rocks, or ash deserts are not
insurmountable. These carnivorous insects must have followed the advent
of required food as was the case of the dozens of dragon flies hovering
over the crater (August 10, 1993). And how about the toads sitting
patiently in the crater waiting for food to pass by? Were they and the
dragonflies and the mosquitoes crater-born or channel-born? Wizard
Island may thus be compared to the House-That-Jack-Built, for this is
the ant lion that ate the ant that lived in the tree that came from the
seed that grew in the pumice that was blown out of the crater that
Wizard Island built. Or, this is the egg, laid by the beetle that came
from the grub, that infested the bar, that belonged to the lodgepole,
that had the "rumor", caused by the spores that came from the parasite
that lived on the paintbrush (for four generations) that grew on the
slope, beside the trail that Jack built. And so one may go on ad
liberatum.
An abundant insect life readily invites
bird inhabitants. The mountain blue bird family on the rim would
indicate that a pair had nested thereabouts. The redbreasted nuthatches
and Oregon Juncos appeared busy and happy. The Calliope humming-bird was
observed sipping nectar from phacelia and fireweed, the Clark nutcracker
probing the cones of the white bark pine on the rim, the marks of the
sapsucker on a white bark pine, and the Cassin purple finch and Audubon
warbler feeding along the evergreened base, the toads near the snow
bank, the coney making hay in the rock slide at the bottom of the
crater, the three golden-mantled ground squirrels near the domicile of
the coney were all dependent "on things" that must have come before.