Impact of forest clearance on the soils of tropical cone karst

The precise nature and effects of forest clearance, followed by a two to three year cycle of shifting cultivation and subsequent secondary re-growth, was observed in an area of lowland evergreen forest over cone karst topography in central Belize. The surface soil properties varied in their response to disturbance but a number of significant changes were measured by comparing the pre-clearance and post-cultivation soil analyses. Four groups of soil properties were identified: (1) organic properties which suffered a marked decrease over the summit and upper slope areas and which showed a tendency to increase towards the foot, (2) alkaline status which demonstrated an increase on the upper slopes, (3) nutrient cations whose levels, from more limited evidence, were generally lower after clearance, particularly in the summit and upper slope areas, and (4) soil physical properties, where both the fine fraction and soil depth were drastically affected by clearance; the proportion of clay diminished on the upper slopes and increased at the footslope zone whilst soil depth thinned at the summit and increased markedly over the foreland. The scale of disturbance is so considerable that it has led to recommendations to limit cultivation and clearance pressure in these vulnerable environments.