Page:Popular Science Monthly Volume 80.djvu/233

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THE GREAT AMERICAN DESERT

one half miles wide by five miles long. They vary in depth from four feet to probably about twenty-five feet. In many of the fresh water lakes the vegetation is encroaching upon the water, so that in time all of the lakes will have disappeared and wet meadows remain. The wet meadows of to-day show this sort of an origin very plainly. Many stages in lake eradication by invading vegetation may be seen in these lake regions. Some lakes are quite free from submerged aquatic plants; others quite free from bulrushes or wild rice; others show belts of these plants about the shore; in others the bulrushes have begun to wander

PSM V80 D233 Alkaline lakes with salt crusted shoreline.png
Fig. 13. Some of the Lakes are so Strongly Alkaline that the Salts Coat the Beach with a White Crust.

into the deeper water, and in still older lakes the water can not be seen because of the complete occupation by the bulrushes and other vegetation. The bulrush is the commonest pioneer in this succession, and it is well fitted for this particular process. Oddly enough it is by the possession of the rhizome type of propagation, the very same character that fits Redfieldia for capturing the blow-out, that the bulrush is enabled to thus encroach upon the open water and finally to capture the lake. In the one case we have a species successfully eradicating a very dry, unstable habitat and in the other case a different species eradicating a very wet, stable habitat by identically the same means. The creeping rhizomes of the bulrush keep reaching into deeper water as the lake bottom is built up until other species are enabled to gain a hold back of the rushes. Thus other species follow in the wake of the bulrushes, and then come the common wet meadow species. At last the water is gone, the aquatic plants are gone, the bulrushes are gone, and the wet meadow plants have full possession of the former lake area