Ecohydrological conditions of wetlands along a precipitation gradient in Patagonia, Argentina

Abstract

Wetlands are an important component of the Andean ecology because of their wealth of biodiversity and endemisms, and the many environmental services they offer. However, baseline knowledge of the types of wetlands and their ecohydrological functioning is currently lacking. Therefore, the objective of this study was to characterize the types and the ecohydrological conditions of wetlands along a precipitation gradient in the Northern Patagonian Andes. This study took advantage of a strong precipitation gradient that occurs due to the rain shadow effect created by the Andes Mountains near the city of San Carlos de Bariloche. We selected five representative wetlands that are at similar elevations and latitudes, but under very different precipitation regimes. At each site, we sampled water and soil chemistry, water levels and floristic composition. We found that hydrological, chemical and vegetation parameters all varied with total precipitation. Sphagnum peatlands occurred in the wettest regions and had year round water saturated soils which formed a peat layer. Meadows were common in the driest regions. We sampled three distinct meadow communities: wet meadows with Juncus balticus, mesic meadows with Festuca pallescens and salt meadows with Distichlis spicata each with a distinct hydrological regime, water chemistry and floristic composition. Marsh/shrub wetlands occurred in the intermediate rainfall areas and had standing water, mineral soils and were vegetated by Nothofagus antarctica and Scirpus spp. Our results indicate the importance of precipitation on wetland structure and function and suggest that any change in precipitation regime will cause significant changes to these ecosystems.