RELATIONSHIP BETWEEN SEED AND SPORE BANKS AND VEGETATION OF A MOUNTAIN FLOOD MEADOW (MALLIN) IN PATAGONIA, ARGENTINA

Soil seed and spore banks are seen to affect the composition and struc ture of plant communities, especially in wetlands. This study was cond ucted in a flooded mountain meadow (mallin) in the Nahuel Huapi Nation al Park, Patagonia, Argentina. Species density and composition were de termined for spring (November 1989) and autumn (April 1990) using the emergence technique. Viable diaspore( i.e., seed and spores) density w as greater for autumn samples (17,063 m(-2)) than for spring samples ( 10,047 m(-2)). A sizeable pool of fern spores was also found, which re presented 17.8 and 60.2% of the autumn and spring collections, respect ively. Species composition of the seed and spore banks varied seasonal ly, and seeds of the dominant mallin species were only present in autu mn. Seed bank species were mostly perennials, except Mimulus parviflor us. The composition of the seed bank compared with that of the above-g round vegetation yielded a relatively low correlation between germinab le seeds in the soil and the surface plant community. In addition, no ferns were present in the surface community. These results suggest tha t neither seed nor spore banks control mallin vegetation dynamics, pro bably because perennial and rhizomatous plants are the dominant compon ents of the wetland community.