Soil variation with altitude on Volcan Barva, Costa Rica

Abstract

Summary Soils were examined from each of six primary forest plots at altitudes of 100 m, 500 m, 1000 m, 1500 m, 2000 m and 2600 m on Volcan Barva, Costa Rica. All were on volcanic parent materials. There was evidence of decreasing intensity of weathering and organic matter decomposition with increasing altitude. Subsoil clay content decreased from 80% at 100 m altitude to less than 10% at 2000 m. Ratios of free to total iron decreased from 0.3 to less than 0.1. Organic matter in the surface horizons increased from 18% to 49% over the same altitude range. The uppermost site at 2600 m was formed on younger and less weathered material and had greater concentrations of exchangeable bases than all the other sites. There was no evidence that the nutrients measured were less well supplied at high altitudes, and forest changes with altitude were not caused by any soil changes examined in this study.