The Effect of Clearing a Tropical Forest Soil

Summary Organic matter in tropical soils under forest is delicately balanced, the continuous addition of fresh material being offset by decomposition. The forest was removed from a soil in Ghana and three degrees of exposure were tested. Chemical and physical properties were measured from 1957 to 1960. Much organic C, total N, and organic P was lost from the soil of fully exposed plots, because soil temperatures increased and fresh organic matter was no longer provided by the forest. Rate of decomposition lessened with time. Decomposition under shade, though still rapid, was significantly slower than in exposed soil. After three years’ exposure the soil produced less mineral N and had smaller cation exchange capacity, exchangeable K, and lower pH than the shaded soil. Exposure also compacted the soil, impeded drainage through the 2–6 in. layer and made the soil erode more easily.