Seedlings dynamics of Festuca spp. in a grassland of Patagonia, Argentina, as affected by competition, microsites, and grazing.

DEFOSSÉ, G.E; ROBBERECHT,R.; BERTILLER, M.B

JOURNAL OF RANGE MANAGEMENT

American Society for Range Management

Año: 1997 vol. 50 p. 73 - 79

0022-409X

The effects of competition, grazing, and microsites on seedlingdynamics of Festuca spp. were investigated in a semiarid steppeof Patagonia, Argentina. In an exclosure and an adjacent grazedarea, the level of root competition for seedlings was controlledthrough root exclusion tubes (0.1 m diameter, 0.4 m long)installed adjacent to 7 similarly-sized Festuca pallescens plantsand in the interspace between F. pallescens plants. Seedlingdynamics at the phenological stages of a) recently emerged andup to 4 leaves and h) 5 leaves and up to 1 tiller were followedinside the tube area (no competition) and in paired circles (competition) for approximately 3 growing seasons. Peak density ofFestuca spp. seedlings occurred in fall and early spring, whenwater content in the first 0 to 5 cm of the soil was above 8%.Seedling densities of Festuca spp. at the 2 phenological stageswere significantly reduced by grazing. At the phenological stageof 1 to 4 leaves, seedlings were not affected by root competition,although their densities were significantly higher for seedlingsadjacent to F. pdescens plants than in the interspace betweenplants. This was due to higher soil water content in these areasthroughout the season in the 0 to 5 cm of the soil. Seedling densities at the phenological stage of 5 leaves and up to 1 tiller weresignificantly higher when there was no competition from neighboring grass plants as compared to seedlings exposed to competition. In regard to microsite differences, seedling density was significantly greater in the interspaces than adjacent to matureplants. These results suggest that although higher seedling densities can be obtained by excluding the area from grazing,intraspecific competition for soil water during the summerdrought period can act as a barrier for further Festuca spp.seedling establishment.