Succession of microconsumers in waterlogged pampean soils (Buenos Aires, Argentina): a microcosm experiment

Abstract

In the present work, the succession of consuming organisms and the dynamics of nutrients in fooded soils were studied in the laboratory. We collected soil samples in a sector of the Salado River middle basin from three topographies (upper, middle, lower) with diferent land uses (agricultural and mixed, involving both agriculture and cattle) that were fooded at dissimilar times. We measured the physical and chemical parameters of the water, nutrients, and chlorophyll a and realized an analysis of the organisms. The reactive fractions of phosphorus and nitrogen increased at the beginning of the fooding, mainly through the agricultural use of the upper topography. Chlorophyll a increased in the intermediate and fnal stages of the fooding in all treatments, with the maximum values being found in the lower agricultural topography. In the 195 taxa recorded, the species richness increased towards the intermediate stage, being slightly higher with agricultural land use. The upper topography exhibited the lowest richness, but the highest densities, due to protist contributions. Rotifers and microcrustaceans were recorded mainly in middle and lower topographies. Trophic-group diversity and complexity increased with decreasing topography and with increased fooding time. We conclude that the residence time of the water in the soil, and the adaptation strategies of the organisms, are key elements in edaphic development and composition during the stages of fooding.