Seasonal patterns in the seed bank of a grassland in north-western Patagonia

The qualitative and quantitative composition of a seed bank in a semi-arid grassland ofStipa speciosaTrinius et Rupecht in north-western Patagonia (Argentina) was studied. The total number of seeds was compared in late summer, winter and spring, both inside and outside a fenced area. Each time the same three species contributed most seed to the bank:Erophila vernaL., with a persistent bank of type III,Rumex acetosellaL., with a persistent bank of type IV, andVulpia australis(Nees) Blom, with a transient bank of type I. The native and dominant species,Stipa speciosa, was among the rarest species in the bank. The highest total number of seeds was found in March (early autumn). A greater number of seeds was found inside than outside the fenced area in the two first sampling months, March and August, whereas no significant difference could be observed in December. Nomenclature:follows Correa M.N. (1969–1988).