Stimulation of Seed-Germination of Understorey Species of the Northern Jarrah Forest of Western-Australia

Abstract

Glasshouse trials in trays of soil measured the germination response to high temperatures and the presence of charcoal in 40 non-leguminous understorey species of the northern jarrah (Eucalyptus marginata Donn ex Smith) forest. Species producing relatively low proportions of viable and germinable seeds tended to be the long-lived resprouting species where reproductive output may not be of major adaptive significance. Three species, Conostylis setosa, Trymalium ledifolium and T. spathulaturn, with seed stored in the soil, were stimulated to germinate by high temperatures. Bradysporous, obligate reseeding species showed either no temperature effect (mainly species of Dryandra) or death at high temperatures (species of Hakea, whose seeds normally are protected by woody fruits). Charred wood of Eucalyptus marginata induced an increase in the proportion of Burchardia umbellata germinating under the test conditions. Relationships of the seed germination results to aspects of r- and K- selection theory and fire management policy in the northern jarrah forest are also discussed.