Effects of forest clearing and land use on soil properties of two land use sequences in Cocori, Atlantic Zone of Costa Rica

Abstract

This report describes the results of a study of the impact of forest clearing and land use on morphological, chemical and physical properties of the soil. Soil profile site studies were done in the Cocori area in the Atlantic Zone of Costa Rica. Two sequences were studied on two different soil types: Cedral (andic humitropept) and Sardina (hydric dystrandept). Emphasis is on soil structure degradation, chemical and physical data related to this degradation and possible recovering of the soil. Sites were chozen in the tropical rainforest, at parts cleared recently from vegetation, in cacao plantations and in grassland. Morphological results are partly based on soil profile descriptions and partly on soil thin section descriptions. Chemical results are based on laboratory analysis of samples and physical results came from infiltration measurements. Conclusions are mainly based on the morphological data: soil degradation because of forest clearing depends largely on the method used for clearing, but if heavy machinery is used and the trees are transported (especially during the rain period) compaction of the soil in inevitable. Land use after clearing will increase degradation as could be concluded from the cacao and pasture sites. Compaction of the soil occurs as structure degradation, dense matrices, lower porosity, less biological activity, water stagnation in the surface horizons and void-degradation. Cultivation of plants is restricted by this compaction due to air-and waterstress. Recovering of the soil structure is possible if vegetation is given a chance to grow as could be concluded from secundary vegetation sites. Older more weathered volcanic soils are more susceptible to soil degration as described in this thesis than younger volcanic soils.