Habitat Segregation by Serotinous Shrubs in Heaths: Post-fire Emergence and Seedling Survival

Abstract

Seeds of two serotinous shrub species generally restricted to the drier edges, and two serotinous shrub species commonly confined to the wetter drainage channels of upland sedge–heaths were assessed for germinability and used in manipulative field experiments. In post-fire field experiments the effects of habitat and manipulated soil moisture were examined to test if the distribution of adult plants was influenced by soil moisture at seed germination. The effects of habitat on seedling survival for 11 months were also assessed. One species from the edge zone, Banksia marginata Cav., and one from the channel zone, Hakea microcarpa R.Br., had germination preferences corresponding to the distribution of adult plants. The other edge species, Hakea dactyloides (Gaertner) Cav., did not show a significant preference for either zone. The second channel species, Callistemon pityoides F.Muell., did not germinate in the field or in a laboratory germination trial. Some evidence for soil-stored dormancy related to temperature and or waterlogging was found in both Hakea species. Overall the results suggest that for two species habitat segregation occurs when seeds are incorporated into the seed-bed and germination occurs. No differential survival effects across habitats were found in the first year of growth.