Seedling recruitment of perennial grasses in degraded areas of the Patagonian Monte

Abstract

The recruitment of perennial grass seedlings in degraded areas of the Patagonian Monte was analyzed. Recolonization of large bare-soil areas by dwarf shrubs or perennial grasses was hypothesized to create favorable microsites for grass seedling recruitment. Under natural field conditions, soil moisture (0-20 cm), root biomass (0-20 cm), the soil seed bank of perennial grasses, and density of perennial grass seedlings in the center of large bare soil areas and in microsites neighboring isolated plants of perennial grasses and dwarf shrubs were assessed. A manipulative experiment was conducted to evaluate seedling recruitment at the 3 microsites with identical density of seed addition of perennial grasses, under situations of root exclusion, and water addition. Under natural field conditions, root biomass did not differ among microsites. Soil moisture, seed density, and seedling density of perennial grasses were higher near perennial grasses than in bare soil or next to dwarf shrubs. Recruitment of perennial grass seedlings did not differ among microsites when the density of seeds did not vary among them or roots of the established plants were excluded. Water increased perennial grass seedling recruitment at all microsites. In degraded areas of the Patagonian Monte the spatial distribution of the soil seed bank followed by water availability are the main limiting factors of seedling recruitment of perennial grasses. Managerial practices oriented to maintain and increase the soil seed bank of perennial grasses, such as grazing exclusion during the grass reproductive period, might contribute to promote the re-establishment of perennial grasses.