Is slope orientation a modifiying factor of floristic structure in the high tropical Andes?

Abstract

We compared páramo communities dominated by Espeletia schultzii contrasting E and W facing slopes, and rainy and dry seasons. Thirty sampling units were randomly established at each orientation. We determined all species present in each sampling unit and estimated the cover of each species using the point intercept method. Additionally, temperature and radiation were recorded at each orientation. In all the different situations (orientations and seasons), four species were consistently dominant: Espeletia schultzii, Hypericum laricifolium, Acaena cylindristachia and Ortachne erectifolia. In addition to differences in species composition and floristic structure, woody species cover was larger at the W facing than at the E facing slope. Species number increased during the rainy season, six and five at the W and E facing slopes, respectively. In spite that most species are perennial, some changed their cover between seasons. We conclude that slope orientation and seasonality modify the floristic structure of the páramo vegetation. These effects should be considered when establishing sampling and conservation strategies for páramo ecosystems.