Regeneration strategies of Triodia spp. in response to fire in the Kimberley, Western Australia

  • Graeme Armstrong

    Student thesis: Doctor of Philosophy (PhD) - CDU


    The processes which structure plant communities enabling species coexistence over time remains an area of active research. Current theory has, at its extremes, deterministic niche and stochastic neutral theory, however several recent explanations reconcile these extremes into stochastic niche theory. Central to this is the recognition that sympatric species have differential regeneration success after a disturbance over both time and space. To investigate this proposition I collected ecological and phenological data on eight sympatric Triodia spp., in the Kimberley of Western Australia, to determine and compare their regeneration responses to fire. Species distributions in the landscape were correlated to habitat variables to determine the degree of habitat specialisation. Regeneration responses to fire were determined through direct observation of natural and experimental fires and the historical coexistence of three species, from different regeneration functional groups, was determined using coalescence analysis. A spatially explicit model, parameterized with the life history matrices of these species, was used to investigate how they competed under a range of fire scales and probabilities. The study demonstrated that
    while the majority of Triodia spp. in this community are habitat generalists,
    differences in relative abundance across different substrates suggests other factors lead to differential competition between species. Strong inter-specific competition was also suggested by species forming mono-specific stands. The molecular analysis demonstrated that species from different functional groups have coexisted since the Pleistocene and the model demonstrated that this can only occur in a narrow range of fire probabilities. Considered together these results indicate that disturbance by fire facilitates the coexistence of these Triodia species. This is possible because each species differentially utilizes opportunities, after fire, arising in the regeneration niche space. Hence, stochastic niche theory best describes the processes operating in
    this community leading to the patterns observed across a range of spatial and
    temporal scales.
    Date of AwardJul 2012
    Original languageEnglish
    SupervisorStephen Garnett (Supervisor) & Sarah Legge (Supervisor)

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