Responses of forest eucalypts to moderate and high intensity fire in the Tingle Mosaic, south-western Australia: comparisons between locally endemic and regionally distributed species

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Abstract

Responses of three locally endemic (Eucalyptus brevistylis, Eucalyptus jacksonii and Eucalyptus guilfoylei) and three co-occurring regional eucalypts (Eucalyptus marginata, Eucalyptus diversicolor and Corymbia calophylla) to moderate- and high-intensity fires were examined in granitic terrain of the Tingle Mosaic, south-western Australia. Significant associations between diameter distributions and community type (CT) for each species (P < 0.001) suggest that fire response will also vary according to the habitat/fire interaction. None of the species were fire sensitive, although responses differed both within and between species, and with CT. All species examined predominately consisted of several cohorts of regeneration within a forest stand. Each species had thick bark and re-sprouted from crown epicormics following 100% scorch of the mature tree. The quantity and type of regeneration in relation to gaps created by individual dead trees following fire differed between species; for example, E. guilfoylei regeneration was strongly associated with gaps, and C. calophylla with non-gaps. However, regeneration of the two tall open-forest species, E. jacksonii and E. diversicolor were not most associated with either gaps or non-gaps. The very low levels of regeneration of E. brevistylis following fire and the high proportion of stems of E. jacksonii that were hollow butted (40% of stems > 1 m DBHOB) may be factors associated with narrow endemism of these species and may affect the vulnerability of these eucalypts to fire. The interaction of seed availability, intense fires and subsequent rainfall may be critical in the long term survival of these species. Eucalyptus guilfoylei, by contrast, appears well adapted to the increasing levels of disturbance likely in the region where these species occur. The vulnerability of a locally endemic species in a fire-prone environment is likely to reflect differences to the prevailing adaptations of the dominant species rather than an inherent ability of the species to survive or respond. Management regimes must account for variations in species responses to fire in different CTs if the long-term survival chances of local endemics are to be enhanced.

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