C. Frank Brockman
Throughout the world, perhaps, no region is better suited to the development of a coniferous forest than is the coastal region of the Pacific Northwest. From Oregon northward to southeastern Alaska and inland to the summit of the Cascades, in the southern portion, and the Selkirks, in the northern portion, one finds climatic conditions more favorable to forest growth than anywhere else in North America. The prevailing winds which sweep inland from the Pacific are heavily laden with moisture which falls as rain at the lower elevations, and as snow at the higher levels, when they rise into the cooler air strata in passing over the mountains which form the eastern climatic boundary of this region. In the coastal region of the State of Washington about 75% of the total annual precipitation fails between October 1 and May 1. In addition to the abundant precipitation, the temperature during the winter is also comparatively mild while the summer, though providing a warm growing season, is characterized by the absence of extended hot periods. This combination is one which is generally agreed to be the best adapted to forest development, and it is because of this that the forests of the Pacific Northwest are so remarkable for the density of the stand and the size of individual species.
As Mt. Rainier National Park lies entirely west of the crest line of the Cascade Range, a part of which forms a portion of the eastern park boundary, its forests are typical of a large part of the north Pacific Coast. Although a large percentage of the original forest wealth of the Pacific Northwest has been cut, the timbered areas of Mt. Rainier National Park are still essentially the same as they were before the first civilized man set foot upon the shores of Puget Sound. And, whatever the future of the forests of the Pacific Northwest may be, the timbered areas within the boundary of this national park will remain as a veritable "outdoor museum" of the magnificent forest of this region which in many respects, was one of the most remarkable in the world. This policy of preserving the native character of this relatively small but representative area is based upon one of the cardinal principles of conservation as practiced by the National Park Service.
Definition Of A Tree.
A tree, as defined by this publication, is a perennial woody plant having a single well defined stem of upright habit whose diameter is not less than two inches and whose height is not less than eight feet when mature. This more or less arbitrary definition eliminates such species of woody plants as the Vine Maple, Mountain Ash, and Trailing Juniper. It confines the species described herein to those which can be readily recognized in this area, by the average individual, as "trees".
Number Of Species Of Trees In Mount Rainier National Park.
On the basis of the above definition, twenty-nine species of trees are native to this national park. Fifteen are of the Pine family (Pinaceae), six belong to the Willow family (Salicaceae), two belong to the Rose family (Rosaceae), while the Yew family (Taxaceae), Birch family (Betulaceae), Dogwood family (Cornaceae), Maple family (Aceraceae), Heath family (Ericaceae) and Oak family (Fagaceae) are represented by one species each. A complete list of species of native trees will be found on page 143.
From the above it is readily apparent that cone-bearing evergreen trees dominate the forests of Mount Rainier National Park. Generally speaking, local forests are composed of a rather complex mixture of a few species and thus are typical of the evergreen forest climax of this section of the north ern Pacific Coast.
Precipitation and Climatic Factors.
Because this publication must, of necessity, be limited in size, only a few general statements relative to the above important features are included here. A more complete account of the climatic features characteristic of Mount Rainier National Park was given in a previous issue of "Nature Notes" (1) and thus, it is unnecessary to repeat that data in detail here.
As already noted the park in common with other areas of like altitude west of the Cascades, is characterized by heavy precipitation. Meteorological data are taken in the park at the Carbon River entrance (1716 ft.), Longmire (2760 ft.), and Paradise Park (5557 ft.). While records for the Carbon River entrance are, as yet, too incomplete for consideration the average annual precipitation at Longmire is about 78 inches while at Paradise Park it is roughly 100 inches (2). In spite of its latitude, which is comparable to northern Maine, and the excessive snowfall, Mount Rainier National Park is characterized by comparatively mild winters. This is largely due to the proximity of the Pacific Ocean and the prevailing westerly winds. The summers, on the other hand are rarely hot for any extended period. The average maximum temperature for Longmire is about 52 degrees; for Paradise 47 degrees. The average minimum temperature for Longmire is about 35 degrees; for Paradise, 29 degrees. The highest temperature ever recorded at Longmire was 105 degrees; at Paradise, 92 degrees. The lowest temperature recorded at Longmire was 9 degrees below zero; at Paradise 20 degrees below zero (3).
Percentage of Timbered Area In Mount Rainier National Park.
Of the 377.78 square miles (241,782 acres) within the boundary of Mt. Rainier National Park, 76.95% or 290.96 sq. mi. is timbered in some form. This includes not only the densely forested areas at the lower elevations but also the subalpine and timberline regions and those areas that have been swept by fire, since the latter are regarded as potential timber areas. Sub-alpine and timberline regions are included because, in a national park, the aesthetic values of the forests at the upper elevations are as highly regarded as are those more commercially important timbered lands at the lower levels.
Forest Types and Associations.
The significant changes in the character of this forest, from the lower park boundaries to timberline, may be readily observed. These changes are largely brought about by differences in climate which are, in turn, caused by variations in altitude. They are further complicated by conditions of soil and moisture which influence the formation of certain forest associations within the four principal timber zones.
Lowland forest: (4) Penetrating the park by means of the principal river valleys this heavily wooded area, impressive in its sombre beauty, great density of the stand, and huge size of individual trees, extends upward to an elevation of about 4000 feet. Occasionally it is not well defined above the 3500 foot level while one sometimes encounters it, particularly on the west side of the park, as high as 4300 feet. This heavily weeded zone occupies 61.03 square miles (39,059.2 acres), 16.17% of the total area of the park.
The principal species of trees are western hemlock (Tsuga heterophylla), Douglas fir (Pseudotsuga taxifolia) and western red cedar (Thuja plicata). Above the 2500 foot level amabalis fir (Abies amabalis) is quite abundant while grand fir (Abies grandis) may also be encountered. While more charaeteristic of the intermediate zone, western white pine (Pinus monticola), noble fir (Abies nobilis) and Alaska cedar (Chamaecyparis nootkatensis) are found as low as 2700 feet. Lodgepole pine (Pinus contorta) is not common but may be readily found in the vicinity of Longmire, and western yew (Taxus brevifolia) is scattered throughout this zone up to 4000 feet, Among the more important deciduous trees is the red alder (Alnus oregona), which is quite abundant in moist locations up to 3000 feet, the black cottonwood (Populus trichocarpa), which is found along streams to nearly 4000 feet in elevation, and the Sitka willow (Salix sitchensis).
It is difficult to portray adequately the magnificence of this lowland forest. So dense are the trees that their branches interlace overhead to form an evergreen canopy to the sun, so that even on warm midsummer days a condition of semi-twilight exists. Great trees rise from a tangled mass of shade loving plants which are sometimes almost tropical appearing in their luxuriance. Others, leveled by age or the elements, sprawl upon the ground, some newly fallen, others festooned with moss and some in the last stages of decomposition. The trails are soft, spongy, and yielding, carpeted as they are by an accumulation of humus and forest litter. It is awe-inspiring in its quiet solitude; cathedral-like in its sombre, peaceful grandeur.
Intermediate forest: This timber zone lies between the dense forests of the park's lower elevations and the park-like sub-alpine meadows. It occurs between the altitudinal limits of 4000 and 5200 feet although, in some instances, intermediate factors may he noted as low as 3500 feet or as high as 5600 feet. A total of 22.86 square miles (49190.4 acres) or 20.41% of the total area of the park, is included in this zone.
The principal species of trees are noble fir (Abies nobilis), Alaska cedar (Chamaecyparis nootkatensis), western hemlock (Tsuga heterophylla), western white pine (Pinus monticola), amabalis fir (Abies amabalis) and mountain hemlock (Tsuga mertensiana). The latter species occurs only in the upper portions of this zone. Engelman spruce (Picea engelmanni) is well represented in this zone but only in the northern portion of the park, particularly on Chenuis Mt., and in the vicinity of the terminus of the Emmons Glacier. While Douglas fir (Pseudotsuga taxifolia) may occasionally be found in the intermediate zone it is not abundant and its upper altitudinal limit is 4500 feet. No deciduous trees are found in the intermediate forest except for an occasional willow. Black Willow (Salix scouleriana) and White Willow (S. lasiolipis) have both been recorded within this zone.
The transition between the lowland and intermediate forest is not sharply defined. However, as one ascends to higher elevations in the park either by road or trail, the change will be readily apparent. The western hemlock-Douglas fir-western red cedar combination has dissolved, Douglas fir is present only sparingly and the western red cedar is entirely absent. Western hemlock is found, but the relative greater abundance of noble fir, Alaska cedar, and western white pine is pronounced. Trees within this altitudinal range rarely exceed 36 inches in diameter and generally they are much smaller while the difference in the luxuriance and composition of the ground cover, as compared to the lower zone, is very evident. Here such plants as the fool's huckleberry (Menziesia ferrugina) and white rhododendron (Rhododendron albiflorum) replace the Devil's club (Oplopanax horridum) and skunk cabbage (Lysichiton camtschatcense), which are characteristic of the lower levels.
Sub-alpine forest: Between 5200 feet and 6500 feet are found The beautiful sub-alpine meadows which are characterized by artistic groups of trees, largely alpine fir (Abies lasiocarpa) and mountain hemlock (Tsuga mertensiana). In certain instances one may find evidence of the sub-alpine forest as low as 5000 feet and as high as 6700 feet. In general, however, its limits lie between the elevations previously noted.
In addition to alpine fir and mountain hemlock, the principal species, one occasionally finds Alaska cedar (Chamaecyparis nootkatensis), amabalis fir (Abies amabalis), white-barked pine (Pinus albicaulis) and, occasionally, lodge-pole pine (Pinus contorta). In the Yakima Park area Engelman spruce (Picea engelmanni) is also present in this zone.
In this zone we find a very evident difference in the forest associations between the Yakima Park area, on the north-east side of Mount Rainier, and the rest of the park. As already stated alpine fir and mountain hemlock are the two principal trees but in the Yakima Park area the mountain hemlock is replaced by the white-barked pine as the chief associate of the alpine fir.
Timberline forest: As the name indicates this zone forms the upper limit of tree growth in Mount Rainier National Park. Timberline factors will be noted as low as 6000 feet in some instances and as high as 7200 feet in others but generally the zone is confined between the 6500 and. 7000 foot levels.
Throughout most of this zone alpine fir (Abies lasiocarpa), mountain hemlock (Tsuga mertensiana) and white-barked pine are the principal species. In the Yakima Park section alpine fir, white-barked pine and Engelman spruce (Picea engelmanni) play the dominant role.
Value Of A Knowledge Of Local Forest Zones and Assocations.
An understanding of the factors that influence the altitudinal limits of the local forest zones and the composition of the varied forest associations within them is of great importance. This is true not only from the standpoint of purely scientific interest, but such knowledge is also of value in the formulation of methods of forest protection. In addition, the average park visitor can better appreciate the plants of this region if he understands, in general, something of the reasons for their diversity and abundance.
Enemies Of The Forest.
The principal enemies of the forest are fire, insects, and fungi. Man should also be included, as his acts are often responsible for forest fires and the introduction of fungus diseases. In areas like national parks, and recreation regions of related character, man also contributes to the decline of the forest by his destruction, intentionally or otherwise, of its ecological balance, particularly in such heavily used areas as camp grounds.
So much has been written about forest fires that the factors which are responsible for them are, or should be, well understood by the general public. As the fire danger is always present during the summer months a vigilant organization is maintained in this national park for the purpose of preventing the occurrence of forest fires or, in the event that they do occur, in locating them as soon as possible so that they may be extinguished or put under control in the shortest possible time. The seven fire lookouts, which are maintained in various parts of the park, are the backbone of this organization. Fortunately, only a few fires of major consequence have occurred in the park in recent years. Perhaps the most disastrous of these is the Sunrise Park burn on the west side in which approximately 2000 acres of timber were destroyed in the fall of 1931. Smaller fires have occurred from time to time but vigilance on the part of the protection organization has held the damage to a minimum.
Before the park was established in 1899 two large fires had destroyed the timber over two very conspicuous sections of the park. In the Stevens Canyon-Cowlitz River area approximately 5000 acres were laid waste but the date and cause of this conflagration is unknown. This is the largest burn in the park. The most famous burn, however, is the "Silver Forest" through which the Paradise Valley highway passes. The name is derived from the silver-grey color of the snags which originally were present throughout this area in great numbers. This, apparently a " "ground" fire, killed the trees by destroying the cambium layer (living tissue of the tree which lies just under the bark). The trunks themselves were not consumed by the flames and they remained standing for many years and weathered to the silver-grey which accounts for the name of tha area. Much of the timber destroyed was Alaska cedar, a very durable weed, and a large part of this was cut many years after the fire took place and utilized in the construction of some of the buildings in the park - notably the Administration Building at Longmire and Paradise Inn and the Paradise Community House at Paradise Valley. Many tales are told concern ing the origin of the fire which caused the "Silver Forest" and, while some are interesting and others amusing, the most logical explanation is that it was started by an untended camp fire in 1885.
With the exception of the destruction of some western white pine by the white pine beetle (Dendroctinus monticolae), little insect damage has occurred in the park. Of course many species of forest insects are known to inhabit this area butt, with the foregoing exception, no widespread damage has resulted.
Western white pine in the park is also suffering from the white pine blister rust and since 1931 efforts have been made to control this introduced fungus disease. Currants and gooseberries, which serve as the alternate host of this disease, have been removed from the vicinity of certain areas where white pine is abundant for, while this species is not particularly abundant throughout the park as a whole, it does occur in considerable quantity at certain locations where its maintenance is very desirable. Furthermore, western white pine is one of the most important species in the reforestation of old burns and considerable quantities of it are found in the "Silver Forest" and in the Stevens Creek-Cowlitz burn through which the highway connecting Paradise Valley and Ohanapecosh Hot Springs will pass.
Interesting Features Of The Forests Of Mount Rainier National Park.
One of the first things that the visitor to Mt. Rainier National Park will notice in the forests of the lower elevations is the great percentage of "clear length" which characterizes the trunks of the large trees. Often these trees will be free of limbs for 100 feet or more. However, one need not seek far for the answer to this. Sunlight is decidedly lacking in this dense stand and the leaves upon the lower branches of these trees die due to this lack. The twigs and, eventually, the branches also die, these being sluffed off as the trunk increases in diameter. Thus "self pruning" causes the clear boles of these trees.
It will also be noticed that, while the largest trees in the deep forests are generally Douglas firs, the relative abundance of this species is low. In addition, few seedlings of the Douglas fir will be found. Again the lack of sunlight is the answer. Douglas fir is an intolerant tree and requires abundant sunlight for its best development. The larger trees that one sees in these dense woods are survivors from the day when Douglas fir was the most abundant tree on the area. Western hemlock, a tree that can grow and reproduce in dense shade, has gradually usurped the place of the Douglas fir. We see evidences of this succession in many places throughout this forest. Where the stand has been opened up by some means or another in the past the Douglas fir is quite abundant but competition in the stand of young trees, brought about by their own density, not only thins out the weaker individuals but enables the more tolerant hemlock to get a foot hold and, eventually, outnumber the Douglas fir.
Throughout much of the intermediate timber zone are large areas wherein the trees are festooned with a lichen known as "goat's beard moss". This, during dry weather, materially increases the fire hazard in those areas, as it dries out rapidly and offers a quick-kindling torch by which fire is rapidly carried into the crowns of these trees.
In the sub-alpine regions the grouping of the trees in artistic and symmetrical clumps will be one of the first features to catch the eye. Each clump is generally made up of a number of large trees surrounded by individuals of gradually diminishing size until, on the outer rim of the group, one finds small seedlings only a few years old. Such groups interspersed by open flower bedecked meadows, are perhaps one of the most attractive features of this zone. Artists and photographers revel in the manner in which they frame a variety of appealing vistas of the alpine terrain. However, these groups did not develop primarily for the benefit of artists. When the cones of these trees ripen and the seeds fall to the ground this area of the park is generally enjoying the first touches of winter; early snows are falling and the seeds, covered by the snow, are prevented from spreading. They are generally held near the base of the parent trees and there they germinate and take root. If two such groups are close together they may, eventually, merge. Upon sloping hillsides the taller trees are usually on the upper portion of the slope for the seeds scatter downhill before coming to rest.
Timberline is also interesting. Often windswept ridges are crowned with a sparse growth of small trees, twisted and contorted by the prevailing winds, while immediately below in a more protected valley one finds the trees conspicuous by their absence. It almost seems as if these trees deliberately choose the most harsh environment possible but, of course, such is not the ease. We may account for this partially by the fact that these exposed ridges represent the first land that was freed from glacier ice and thus the first haven for plants. It may also be due to the fact that the steep slopes of the valleys immediately below are more inhospitable to the establishment of trees due to the sliding of deep snowdrifts which prevent seedlings from becoming established. In addition, as the ridges were the first to be freed from the glaciers, so they are the first to be freed from winter's snows. These and many other factors account for the presence of trees in such exposed locations.
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(1) Glacier Recession in Mount Rainier National Park. Mount Rainier National Park "Nature Notes"; Vol. 15, No. 4. December 1937. C. Frank Brockman.
(2) This includes the annual snowfall for this region. At Longmire the average annual snowfall is about 15 feet, the maximum depth at any one time varying from 2-7 feet. At Paradise Valley approximately 50 feet of snow falls annually, the maximum depth at any one time varying from 15-25 feet. On April 2, 1917 a maximum depth of 27 ft. and 2 inches was noted, being the greatest so far recorded.
While no records are available for Yakima Park, (6400 ft.) casual observations over the past five or six years indicate that although this point is 900 ft. higher than Paradise, the snowfall is considerably less. Ten to fifteen feet is the usual maximum depth at any one time at Yakima Park.
(3) See Glacier Recession in Mt. Rainier National Park, Mount Rainier National Park "Nature Notes"; Vol. 15, No. 4, December 1937.
(4) The term "lowland" is used in its relative sense as compared to other timber zones within this national park.
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