Ecosystem resilience towards climate change - the role of interacting buffer mechanisms in Mediterranean-type ecosystems

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Ecosystems are known to exhibit buffer mechanisms that reduce the impact of disturbances on vegetation and that prevent the system from easily shifting from one state to another. Buffering mechanisms can occur on the level of the population (e.g. trait variability), on the level of the community (e.g. substitution of one species by another with the same function), or on the level of the landscape (e.g. refuge sites, self organization). Although the role of single buffer mechanisms has been studied in several ecosystems, a thorough analysis of interacting buffer mechanisms on various scales is missing. Therefore, we often do not know what stabilizes ecosystems under present conditions and how this could change in the future.The aim of this project is therefore to first evaluate buffer mechanisms on different levels of an ecosystem in the species-rich Mediterranean-type shrublands of the Eneabba sandplain in south-western Australia and then to develop a general theory of buffer mechanisms in Mediterranean-type ecosystems. The Eneabba sandplain is a global biodiversity hotspot and consists of a landscape of dunes and interdunes covered by dense and spatially heterogeneous shrub vegetation with regular fire events that drive recruitment. In this project, we want to particularly understand the interacting mechanisms that stabilize this and other ecosystems against harsh environmental conditions and how the importance of each mechanism will shift under climate change. For this, we will develop an ecohydrological model, which simulates the spatially heterogeneous coupled dynamics of water and vegetation. The model combines the advantages of two existing models (Eneabba vegetation: Esther et al. 2008, 2010, 2011; ecohydrology: Tietjen et al. 2009, 2010, Lohmann et al. 2012), and its development and application will be closely accompanied by extensive field measurements and experiments of cooperation partners on soil moisture, water fluxes and vegetation dynamics under present and possible future climate conditions. Model experiments on trait variability, species composition and landscape heterogeneity will then help to asses the drivers of resilience under present conditions, to disentangle impacts of single buffer mechanisms, and to assess the role of different buffer mechanisms under climate change and the future resilience of the ecosystem. This will not only improve our site-specific knowledge of ecosystem dynamics, but will also provide a novel base to understand buffer mechanisms and their interactions in general.