Aspects of the dynamics of the seed‐banks and seedling populations of Acacia victoriae and Cassia spp. in arid western New South Wales

Acacia victoriae, Cassia nemophila and C. phyllodinea are shrubs which occur throughout large areas of arid and semi‐arid Australia. This paper examines aspects of the dynamics of the seed‐banks and seedling populations of these plants to determine their influence upon recruitment frequency. Seed‐banks in the soil are large, ranging from 50 to 3900 seeds m^‐2for A. victoriae and from 5 to 400 seeds m^‐2for Cassia spp. A large proportion (ca. 80%) of these seeds are viable. Seedling densities soon after emergence range up to 25.7 m^‐2for A. victoriae and up to 21.7 m^‐2for Cassia spp. Any individual cohort of seedlings represents only a small proportion (< 6%) of the total seed‐bank. Most viable seeds fail to germinate even when adequate moisture is available. Seedling mortality rates are high (ca. 100%) during the first 12 months after germination. If recruitment of these shrubs is intermittent, it is most likely a result of low seedling survival rather than infrequent germination.