| Abstract: | Germinable seed densities in the surface (0–10 cm) soil of pasture communities growing at Lansdown, near Townsville, were measured during the late dry season before the first germinating rain and again during the following wet season after germination but before the input of new seed. Seedlings emerging in the field were counted at approximately weekly intervals during this period to determine emergence patterns. Twelve communities were sampled in 1980–81 and six were re-sampled in 1981–82. During the late dry season germinable seed densities ranged from 5000 to 40 000 seeds m-2. Seeds of the introduced legume, Stylosanthes hamata, were present in all pastures. There were many seeds of annual grasses (Digitaria ciliaris and Brachiaria miliiformis) and sedges (Cyperus and Fimbristylis spp.) but only few seeds of perennial grasses (both native and introduced). Soil seed densities were much lower during the wet season than during the preceding dry season, particularly for the grasses. Emergence commenced and approximately 70% of all seedlings emerged on the first major rainfall of the wet season. The subsequent emergence pattern varied between years. In 1980–81 there was a gradual and continuous increase in seedling numbers under the continuously moist conditions which prevailed. In 1981–82 further emergence occurred in discrete events related to rainfall and intervening dry periods. Maximum seedling densities exceeded 34 000 seedlings m-2 including 29 000 grass seedlings (mainly annual species). The implications of these results for species survival and pasture composition are discussed. |
