By Donald Edward McHenry, Junior Naturalist
ONE CAN NEVER forget the north rim of the Grand Canyon in autumn. Driving along its enchanted scenic highways, one's fancy is intrigued by the varied colors of the turning aspen trees set deep in the somber green of the dense forest of tall spruces and firs. They appear almost to be patches of sunlight hurriedly left behind by a sun too eager to sink to rest after its day's journey.
Equally memorable is the sight of the Kaibab Forest at this time of the year as one skims over it in an aeroplane. Stretching to the very brink of the canyon and, in some places, even lopping over into the chasm, one sees an artist's dream in shades of yellow, red and burnt orange; dashes of brilliant color snugly nestled in the deep green carpet of the evergreen forest.
The quaking aspen, Populus tremuloides, is fascinating in all its various moods. It is among the foremost harbingers of a belated spring which, in its yearly visit to the Grand Canyon, reaches the north rim last of all. Wandering over the floor of the valleys in that area during the early part of June, one is surrounded by the slender white trunks of the aspen - trees not yet awakened to the advent of spring. But as one looks up the slopes on either side he can barely detect a delicate green haze beginning to appear in the tops of the aspen which grow high above. Each successive day brings a richer green to these pioneers, while the fresh spring color flows deeper and deeper into the valley. After two or three weeks even the most reluctant individuals along the bottom respond to the urge of spring and the whole region is at last clothed in the shimmering green so characteristic of the quaking aspen.
This change does not appear, however, at the same rate on both sides of the valley. The trees on the north facing slopes are just a little slower in acquiring their leaves than those on the opposite slopes. The north facing ones do not receive so much warmth as those facing the direct rays of the sun. Another interesting effect of temperature differences is the relative rate of development seen between the top and bottom of the valley, as already suggested. This is explained by drainage of the cold air into the bottom of the valley, while the higher parts are warmer and more favorable to an earlier showing of spring growth.
It is not clearly evident that this order of development is reversed when autumn creeps into the valley as would be expected. Here and there a single branch of the aspen will stand out conspicuously as a golden wand against the quivering green of the leaves still in their summer color. This may appear on any part of the tree or be found on any part of the hillside. Occasionally a person may be led to suspect that there is an almost imperceptible tendency for the autumn colors to first appear on the north facing slopes, but such cannot be proved.
The relationship of the aspen to our common cottonwood tree is suggested in the habit of the female trees giving off spring showers of cotton-like material which bears the fruit. At times this is so conspicuous that the immediate territory seems to be enjoying a light, warm snowstorm. Ranger Ed Laws has reported that this "snow" has occasionally piled up in the corners of some of the government sheds to the depth of several feet.
If one is at all observant as he tramps through the aspen groves on the north rim of Grand Canyon, he will notice that most of those trees which grow on the sides of hills have such curving trunks just above the ground that they appear to have started growing downhill before they assumed a perpendicular position. This downhill sag is undoubtedly due to the force of snow as it pressed against the trees while they were very young. It has been suggested that the almost corkscrew twist which is so characteristic of some of the aspen stems is also the result of the weight of the snow on the young stems. This will bear more study.
It sometimes seems strange that the aspen trees thrive so well in a climate in which the hazards of snow are so great. Occasionally we do find oases where these trees succumb to such dangers. Persons who have visited Point Imperial during the past summer have been curious about the aspen trees which have been broken down in great numbers along the road. In some cases they are bent over in such a manner that they form an arch over the highway. This is the work of the snow last winter. With a total fall of about 210 inches on the north rim of Grand Canyon, the weight of the accumulated mass snapped the brittle trunks of these trees. At first some hopes were held for the recovery of at least a few of them, but the writer has noted no improvement in their condition. In fact they seemed to lean more as the sap ascended the stems and the leaves appeared.
It may interest those who enjoy our white-barked aspen to know that there is a legend which is suggested by Populus, the scientific name of this tree and others of the same family. Dr. Francis Ramaley of the University of Colorado tells it somewhat as follows: In the days of the Roman Empire there were many holidays celebrated by the people as a whole. It became the custom to plant trees on some of these occasions as part of the ceremonies of celebration, possibly to commemorate some deity or hero. The tree which became most generally used by the people, a tree evidently belonging to the aspen or cottonwood family, soon was known as the tree of the people, or in latin, populi. Today the name comes down to us as the generic scientific name Populus. It is the corruption of this name which accounts for the common name Poplar tree. There may possibly be some truth to this legend.
Populus tremuloides or quaking aspen gets its name from the trembling habit of its leaves in the slightest breeze. This activity is caused by the manner in which the petiole of the leaf is attached to the leaf blade. At the point of attachment the petiole is compressed at right angles to the plane of the leaf blade, thus allowing it to give with the slightest air current.
The manner in which the leaves of the quaking aspen tremble gives an excuse for still another legend. The story is that the wood of this tree was used in building the cross for the crucifixion of Jesus. Because of its ignominious duty, its leaves have been doomed to quiver in shame ever since.
|<<< Previous||> Cover <||Next >>>|