CONICET | Buscador de Institutos y Recursos Humanos

In Patagonia, meadows are the most characteristic type of wetland, with very important ecological and productive roles. Their high primary production makes them extensively used systems, leading to historical overgrazing. Currently, there are no studies on the potential of seed banks of meadows under productive use. The objective of this work was to study the size and composition of the seed bank of a meadow located in the NW Patagonian steppe. Two plant communities (one dominated by Juncus balticus= Junco, and the other by Festuca pallescens= Festuca), and three different grassland conditions (Good, Fair, Poor) were considered. Standing vegetation was recorded and two soil seed banks assays were performed using the seedling emergence technique. Both seed banks were similar in size and richness, with 8900 seedlings/m2 and 18 species in autumn, and 8552 seedlings/m2 and 16 species in spring. The lack of similarity found between standing vegetation and seed bank indicates that the former does not have an important role in the vegetation regeneration dynamics, and vegetative propagation is the main strategy for dominant species to mantain their populations. The species most abundant and more widely distributed in the seed banks were scarce or absent in the standing vegetation and follow the strategy of forming persistent banks. Junco community is the major reservoir of biodiversity of the meadow, possibly related to the transport of propagules from other sectors of the basin. The results observed in the seed bank showed a direct relationship with the rangeland condition, being more evident in the community of Junco, where moderate changes in the range condition produce significant changes of the species. This, coupled with the low possibility of revegetation from seed bank, demonstrated the susceptibility to deterioration of the plant communities in this ecosystem.