National Geographic : 1897 Jul
THE FORESTS AND DESERTS OF ARIZONA a very general and interesting phenomenon throughout these woods, furnishing not only most pleasing vistas but opportunity for pasturage and agricultural use. Their soil is usually rich black loam washed from the surrounding hills, rather compact and liable to a wide range of moisture conditions on account of deficient drainage, and hence inimical to tree-growth, but readily supporting a greensward of grass. In wet seasons these depres sions sometimes turn into lakes. Mormon lake, which we pass, is such a prairie, some five miles long and one to two miles wide, which, when the Mormons arrived there, had the appearance of a rich meadow, inducing them to settle and go into dairy farm ing; after a few years the glade filled up with water and became a lake; in 1895 it was all dry except a small remnant of water in the lowest depression. As these patches of fertile land, forming about 15 to 20 per cent of the forested area, are destined to be come objects of agricultural development-they have begun to be so used-and in that way to be helpful in the rational man agement of the surrounding forest country, it would be of inter est to experiment as to their best treatment; many of them by judicious ditching, by which the moisture extremes may be abated, can undoubtedly be made to produce various crops be sides the potato and alfalfa or oats which the short season and the cold condition of the soil now permit. As we proceed we presently pass a most forbidding spot, where the limestone soil is covered with black blocks of lava, giving rise to soils locally known as malapai, corrupted from the Span ish mal pais, bad lands, although the soil is not so bad after all, at least for tree-growth. One of the great lava fields of the world, made up of basalt and trachyte, extends from San Francisco mountains southward and northward, covering fully 20,000 square miles with its overflow. As we progress through the forest we learn from the differences of soils and consequent differences in development of the trees something of the geology of this plateau. Archaean, Silurian, Carboniferous, Juratrias, Cretaceous, and igneous rocks are found. Three soil formations are readily recognized -limestone here, sandstone there, and over both, irregularly, the decomposed beds of lava which have overflowed thousands of square miles, giv ing rise to the malapai. So far as tree-growth is concerned, wher ever the decomposition of the lava blocks has been thorough and limestones have added their quota, the soil is by no means unfavorable. The limestone soils seem to produce the best timber, the sandstone soils the poorest.