Impact of Fire on Geophyte Abundance, Diversity and Composition in the Jarrah Forests of South-West Western Australia
KeywordsFire ecology -- Western Australia -- South-West
Forest ecology -- Western Australia -- South-West
Jarrah -- Ecology -- Western Australia -- South-West
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AbstractWithin fire-prone environments, such as the dry sclerophyll forests of south-west Western Australia, species morphology and distributions have established and maintained long-term dynamic relationships with fire regimes. These fire regimes can alter ecosystems, creating spatial and temporal changes in species composition, structure and fuel accumulation at both local and landscape scales. The cessation of Indigenous fire regimes and the establishment and expansion of a fire vulnerable European society produced the need for fire management strategies such as prescribed burning to be implemented to ensure protection of life, property and other values. Concurrent with these human-focused objectives has been the ever-increasing goal of utilizing these methods for maintaining biodiversity in the long-term. For prescribed burning to meet the goal of maintaining biodiversity at varying landscape scales, efforts are needed to gather information on taxa where little to no knowledge on fire ecology exists. One group of organisms that is poorly studied in relation to fire ecology are the geophytes, which contribute a significant portion of the south-west flora. The aim of this research was to address five key objectives via a space-for-time survey, monitoring the impacts of fire on geophyte populations in the southern jarrah forests, at two experimental sites (Perup and McCorkhill) established and maintained by the Department of Conservation and Land Management. The first three interrelated objectives sought to determine the impacts that time since last fire, frequency of fire and season of fire have on geophyte abundance, diversity and composition. The fourth objective was to determine whether ecosystem structure and microclimate are as important to geophyte populations and species assemblages as the direct effects of fire itself. The fifth objective was to ascertain whether microhabitats such as large, fallen burnt logs are used as refuge areas by geophyte species. The results of this study indicated that geophyte species assemblages were decidedly different between plots experiencing the same fire treatment, and spatially distributed in a very patchy nature within treatment plots. As such, geophytes could be responding to fine-scale microclimate variations in such things as fire intensity, burn duration, fire effects on the availability of nutrients and fire impaction through changes in community structure. Overall geophyte species richness was shown to peak 5-10 years post-fire within the two treatment sites. Total geophyte assemblages were found not to be significantly affected by variations in fire treatment, although individual geophyte species did display a significant preference for different fire ages and fire frequencies. Microhabitats such as large, fallen burnt logs were identified as vital refuge areas within a more dry and open jarrah complex. It is hoped that the knowledge gained from this study will enable fire management plans to continue to adapt and improve by including new research on areas where scientific data has been lacking. New generalisation that can be obtained from this research will hopefully guide the conservation and management of geophytes and hopefully protect their long-term abundance, diversity and composition.