Steepland resources: characteristics, stability and micromorphology

Steeplands of Central America are a major land resource, but due to population pressures they are rapidly being deforested leading to landscape instability. Microwatersheds of Southern Honduras were examined to correlate soil type, landform, slope gradient and slump potential. Soils most susceptible to slumping were moderately deep (0.5–1 m) Haplustalfs and Haplustepts. These soils occupy about 25% of the landscape, and have slope gradients of 45–90%. Soils are developed on plagioclase-rich andesitic parent material, are loam to clay loam in texture and have high base status. However, due to weathering of parent material, sand and silt fractions are dominated by quartz with smaller amounts of plagioclase, vermiculite and kaolinite. The A and B horizons have an open porphyric related distribution with plagioclase as the coarse fraction in a fine-grained groundmass. The andesitic parent rock contains abundant hydrothermally altered plagioclase phenocrysts in a single-spaced porphyric-related (c/f5μm ratio of 4:1) distribution. Some feldspars are partially to completely altered to clay pseudomorphs, probably vermiculite. Microfabric analysis of soil and pararock did not show any striated b-fabric indicative of shear failure. However, microfabrics do confirm translocated clay into the subsoil as typic pore coatings indicating long-term landscape stability prior to deforestation.