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  • Final Activity and Management Report Summary - PLANT METAPOPULATION (Understanding plant diversity maintenance in a multi-species metapopulation system in highly variable fire prone environment)

Final Activity and Management Report Summary - PLANT METAPOPULATION (Understanding plant diversity maintenance in a multi-species metapopulation system in highly variable fire prone environment)

Understanding plant diversity maintenance using multi-species metapopulation models in highly variable fire prone environments. Mediterranean-climate ecosystems (e.g. Mediterranean Basin, Southwest Australia) are biodiversity hot spots for vascular plants. Some fire-adapted plant species of the Proteaecae family of the South African Cape floristic region and the Southwest Australian sandplains, which are killed by fires (non-sprouters) and store their seeds in canopies (serotiny), are one of the rare examples of genuine plant 'metapopulations', i.e. several spatially separated populations are linked by dispersal and local extinction can be compensated by colonisation from one of the surrounding populations. In addition to the fire-killed, serotinous, shrubs other adaptations to fire have evolved; for example, resprouting species have the ability to survive and to resprout after fire from belowground tissue.

The biodiversity of Mediterranean-type ecosystems is under severe and increasing threat (e.g. invasive species, habitat loss and climate change). In order to improve the conservation of such multi-species metapopulation systems, a sound understanding of the key ecosystem processes, such as disturbance, is essential to help to develop appropriate management strategies. Simulation studies are an excellent tool for summarising the available (empirical) data and expert knowledge, and then extrapolating this information to the temporal and spatial scales relevant to management and conservation planning. In contrast to previous conceptual multi-species metacommunity models, this study is based on long-term comprehensive field data and expert knowledge from Mediterranean-type shrublands of the Eneabba Sandplain, South-western Australia.

A rule-based simulation was developed to answer, among others, the following research questions: Which processes facilitate the maintenance of (high) species diversity in a fire-prone multi-species metapopulation? How robust and/or resilient is the species community to changes in the fire regime? The model is a grid- and rule-based simulation model. The model arena represents 16 square kilometres (1,600 grid cells) and typically the simulation time is 10,000 years (annual time steps). Each grid cell can either be habitat - and accommodate a plant community - or can be uninhabitable (matrix). A local community consists of cohorts of species that belong to one of two Plant Functional Types (PFT): 1) non-sprouters that are killed by a fire and 2) resprouters that survive fire with a certain probability.

Each year a fire occurs in the system. Fire spread is explicitly modelled by a percolation model. After a fire event all burnt cells will be updated and all non-sprouters will die and disperse their seeds. In any given fire only a fraction of the resprouters will die, but all resprouters will disperse their seeds. Most seeds of either functional type remain in the local community, but some seeds are distributed in the meta-community by long-distance dispersal events, which are surprisingly frequent in the studied system. One key result is that different species of resprouters and non-sprouters can coexist under a variety of environmental conditions (fire regimes) so long as there is a positive correlation between the survival probability of resprouters and the number of offspring of non-sprouters.

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