Abstract
Riparian areas are temporally and spatially heterogeneous ecosystems which favor high species’ diversity; however, they may be affected by the intensification of certain anthropogenic perturbations. With the aim of generating basic information to assess the effects of possible disturbances, riparian vegetation is characterized in terms of growth form, and three of its aspects are analyzed: diversity at three scales (bank, reach, and watershed), relationship with topographic and soil variables, and changes associated with livestock presence. In this study, 130 taxa were identified; among them, Cynodon dactylon and Eleocharis spp. exhibited frequencies close to 100% and the highest coverage level. Of all the species, 51% were perennials, 27% macrophytes and amphibious plants, 18% annual plants and 3% trees. The proportion of exotic species is not lower than that of pampean grasslands, but macrophytes and amphibious plants are almost all natives. Beta diversity, calculated as the ratio between reach and stream-banks, was 1.37, and for watershed/reachs, 1.89; thus, beta diversity contributes significantly to regional biodiversity. In a principal component analysis, bank slopes explained the greater proportion of variability among sites. Nevertheless, diversity was correlated to the soil-variables axis. The Rio de la Plata watershed was the most diverse, and was differentiated from the other watersheds in a discriminant analysis, primarily on the basis of soil-bulk density. We suggest that the functioning of riparian areas be considered at the watershed scale for the design of research projects and management strategies.
Highlights
Las principales perturbaciones de las riberas en la Pampa Ondulada son la invasión de acacia negra (Gleditsia triacanthos L.) y la presencia de ganado vacuno
Ambos fenómenos se han acelerado en los últimos años, por un lado a raíz de las características de la acacia que le permiten expandir su área de distribución rápidamente y por el otro, a causa de la intensificación de la agricultura que desplaza la explotación ganadera a zonas bajas (Di Bella et al 2014) y favorece el uso de los arroyos como abrevaderos
Monographs in Systematic Botany from the Missouri Botanical Garden 47:1-178
Summary
Diversidad de la vegetación y características morfoedáficas de las riberas de arroyos pampeanos. Con el propósito de aportar información de base, que permita evaluar los efectos sobre la biodiversidad de eventuales disturbios, se caracteriza la vegetación por sus grupos biológicos y se analizan tres aspectos: la diversidad a tres escalas (margen, tramo y cuenca), su relación con características topográficas y edáficas y los cambios asociados a la presencia de ganado. En este trabajo no se consideraron los sitios con acacias, donde las comunidades herbáceas son distintas por estar sometidas a presiones ambientales diferentes a las del pastizal, pero sí se evaluaron los cambios en la vegetación asociados a la presencia de ganado. Esta investigación tiene como objetivos a) caracterizar la vegetación de las riberas de acuerdo con sus grupos biológicos y b) analizar su diversidad a tres escalas espaciales (margen, tramo y cuenca), analizar la relación de la vegetación con las principales variables topográficas y edáficas de las riberas, y relacionar las características de la vegetación con la presencia de ganado
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