EFFECTS OF TOPOGRAPHY, SOIL-MOISTURE, WIND AND GRAZING ON FESTUCA SEEDLINGS IN A PATAGONIAN GRASSLAND

The effects of topography, soil moisture, wind and grazing on the emer gence and survival of seedlings of Festuca spp. were examined in the s teppe zone of Patagonia, Argentina. Ungrazed and grazed field treatmen t plots were established on a plain and a north-facing slope at the Me dia Luna Ranch (43 degrees 36' S, 71 degrees 25' W). On the leeward an d windward sides of each of 15 Festuca plants, 0.1 m x 0.4 m quadrats were censused bimonthly for seedling emergence and survival over three growing seasons. Three categories were distinguished: recently germin ated and up to the first leaf, two to four leaves, and from five leave s up to one tiller. Soil moisture content, litter cover and frost heav ing effects were also determined for each treatment at each sampling d ate. Festuca spp. showed two emergence peaks, one in rate fall and the other in early to mid-spring. Seedling emergence was significantly co rrelated with soil moisture content in the 0-5 cm of the soil during t he three growing seasons. Seedlings that emerged in the fall had highe r survivorship than those that emerged in spring. Seedling emergence a nd survival was significantly (p < 0.01) lower on slopes, in the grazi ng treatment, and on windward sides of adult plants. In this grassland , an increase in the availability of safe sites for seedling emergence and survival might be achieved by protecting vegetation from grazing, particularly on north-facing slopes.