Fire-Driven Extinction of Plant Populations: a Synthesis of Theory and Review of Evidence from Australian Vegetation David Keith NSW National Parks & Wildlife Service, PO Box 1967, Hurstville 2220, NSW. Current Address: Parks & Wildlife Service, GPO Box 44A, Hobart 7001, TAS. Keith, D. (1996). Fire-driven extinction of plant populations: a synthesis of theory and review of evidence from Australian vegetation. Proc. Linn. Soc. N.S.W. 116, 37-78. Much of Australia's native vegetation is prone to recurring fires. Any desire to con-serve the diversity of Australia's fire-prone plant communities must be backed by an under-standing of how various regimes of fire affect processes that drive population and community change. Only with such understanding is it possible to predict which fire regimes are associat-ed with high probabilities of population declines and extinctions so that these may be avoided in management. Several ecological concepts contribute to our ability to predict these out-comes. These include: description of temporal and spatial patterns of fires in terms of their frequency, intensity, season (fire regimes); characterisation and analysis of vegetation change in terms of population processes; and the definition of life-cycle attributes that allow species with similar responses to fire regimes to be classified into functional groups. Using a demographic approach, I identified a number of fire-driven mechanisms of plant extinction. These include seven mechanisms related to death of standing plants and seeds, four mechanisms relating to failure of seed release and/or germination; four mecha-nisms relating to failure of seedling establishment; two mechanisms relating to the interrup-tion of maturation or developmental growth; and three mechanisms relating to the failure of seed production. These processes may interact with each other, with co-occurring organisms, and with stochasticity in the physical environment. Such interactions may result in accelerat-ed rates of population decline. Fire regimes associated with multiple mechanisms of plant population decline and extinction include high frequency fires, low frequency fires and repeated fires that result in little vertical penetration of heat and possibly smoke derivatives. Many deficiencies remain in knowledge of the effects of fire on plant species and communities. Despite these deficiencies, mechanisms of plant extinction and the fire regimes with which they are associated are sufficiently well understood that they, along with existing theories of diversity and practical management tools, provide a strong scientific basis for the management of fire for conservation of plant populations and communities. Manuscript received 1 May J 995, accepted for publication 22 Nov 1995. KEYWORDS: fire-regime, plant extinction, conservation, demographic analysis, plant popu-lation decline INTRODUCTION The influence of fire extends through virtually all terrestrial habitats in Australia, as it does in many other tropical and temperate parts of the world. In these areas fire may be viewed as an ecological process that mediates between maintenance and loss of bio-logical diversity (Gill and Bradstock 1995). It is one of the few such processes that may be manipulated so readily (though not always successfully) by humans (Shea et al. 1981, van Wilgen et al. 1994, Bradstock et al. 1995), as indeed it has been over millennia to meet a wide variety of ends (Kohen, this volume). In Australia, conservation of biologi-cal diversity has become an explicit goal of contemporary fire management in many nat-ural areas under public ownership (Shea et al. 1981, Conroy, this volume, Moore and Shields, this volume) and some areas under private ownership. The fulfilment of this Proc. Linn. Soc. n.s.w., 116. 1996
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