Post 22449
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While forest fires bring many of these parks, others are glacier meadows, lake-basins which time has filled with sediment and sodded with grass. Many are due to the presence of water, either outspreading surface water or an excess of underground water just beneath the surface,–to streams visible or invisible. A few result from boggy places which result from impaired drainage caused by landslips or fallen trees. Thousands were made by beaver dams,–are old beaver ponds that filled with sediment and then grassed over.
Most parks that owe their origin to forest fires have charcoal beneath the surface. A little digging commonly reveals charred logs or roots. Occasionally, too, a blackened tree-snag stands suggestively in these treeless gardens. In the competition for this territory, in which grass, spruces, aspens, and kinnikinick compete, grass was successful. Just what conditions may have been favorable to grass cannot be told, though probably one point was the abundance of moisture. Possibly the fire destroyed all near-by seed trees, or trees not destroyed may not have borne seed until the year following the fire. Anyway, grass often seizes and covers fire-cleared areas so thickly and so continuously with sod that tree seeds find no opening, and grass thus holds possession for decades, and, in favorable places, possibly for a century.
Trees grow up around these areas and in due time the grassy park is surrounded by a forest. The trees along the edge of this park extend long limbs out into it. These limbs shade and kill the grass beneath. Tree seeds sprout where the grass is killed, and these seedlings in turn produce trees with long limbs reaching into the park. These shade and smother more grass and thus advance the forest another limb’s length. Slowly but surely the park is diminished.