POSTFIRE SEED BANK IN RELATION TO RAINFALL AND TEMPERATURE IN NORTHWESTERN PATAGONIA GRASSLANDS

GONZALEZ S.; GHERMANDI L.; BECKER G.

Congreso; V Reunión del grupo regional patagónico de ecosistemas de pastoreo; 2003

Fire is an integral component of the vegetation dynamics in Northwestern Patagonia grasslands. Precipitation and temperature that are registered in the post-fire years influence on the seed production from the plants that integrate these grasslands. During three years we evaluated the relation between density and richness of the post-fire seed bank, and precipitation and temperature registered during the growing season (September to December)and during winter period (May to August). The study was carried out in a grassland in Northwestern Patagonia dominated by Stipa speciosa and Festuca pallescens, which was burned in January 1999. Samplings were taken in April 1999, 2000 and 2001, in two different sites: Control site (C) and Burned site (B). Samples were submitted to cold stratification and then were left to germinate in a greenhouse the following spring after samples were taken. The emerged seedlings were identified, counted and removed weekly. To analyse the results the number of seeds of each species (estimated as number of emerged seedlings per m2 ) were grouped in five functional groups: annual forbs, perennial forbs, annual grasses, perennial grasses and shrubs.In both sites, 2000 and 2001 seedbanks presented a significantly higher total number of seeds/m2 (TNS) than the values for the 1999 seedbank (p