Grass and timber soils distribution in the Big Horn Mountains
1930
Dunnewald, T.J.
1. Grass vegetation in the Big Horn Mountains produces dark-colored acid soils with large amounts of colloidal black organic matter. When invaded by timber, the organic matter from the trees starts a leaching process which reduces the soluble organic and mineral content of the soil. Timber will invade either acid or basic soil and its tendency is to increase the acidity of acid soil or to decrease the bases in a basic soil. 2. Timber invasion removes iron, aluminum, and phosphorous less rapidly and calcium and magnesium more rapidly from a basic soil than from an acid soil. This process makes acid timber soils less fertile and less productive grazing land than the grass soils of the mountain areas. 3. This difference in fertility is shown by the greater nitrogen content of the organic matter of the grass soils and by the greater amounts of available phosphates in them. 4. The data seem to show that the bases are more actively removed by organic matter placed on top of the soil than when intimately mixed with it. Iron, aluminum, and phosphorous are removed less rapidly under these conditions in the basic soil and more rapidly in the acid soil.
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