| Résumé: | The effects on soils of two caulescent rosette species, Coespeletia timotensis and Espeletia schultzii, were studied along a slope toposequence in the Venezuelan Andes. All soil properties examined, except texture, were significantly affected by the presence of plants, but the first species had a stronger influence than the second. This resulted from greater accumulation of organic matter under C. timotensis, which has a larger biomass than E. schultzii. When compared to adjacent bare soils, organic matter, cation-exchange capacity, and total N doubled beneath the first species but increased < 29% below the other. Soil color became darker, and bulk density dropped about 14%, under both species. Concentrations of exchangeable bases (Ca, Mg, K) increased from 4 to 31 times below timotensis; available Ñ increased 2 to 5 times. Soil pH was raised by 0.7 units, and percentage of base saturation (PBS) was 2 to 3 times greater than in control soils. In contrast, cations below E. schultzii only increased from 38 to 260%, and P was not affected. Soil pH was raised by 0.08 units, and PBS by only 8.6%. The general effect of the Andean rosettes was to produce soils which resemble those found on lower slope segments, but the influence of plants was considerably more pronounced than that of topographic position.
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