Modeling the role of climate change on small-scale vegetation patterns in aMediterranean basin using a Cellular Automata model

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Predicting vegetation response in regions of ecotone transition under a changing climate is a among grand challengesin ecohydrology. In a small basin (1.3 sq km) in Sicily, Italy, where north-facing slopes are characterizedby Quercus (tree), and south-facing slopes by Opuntia ficus-indaca (evergreen perennial species drought tolerant)and grasses we use an ecohydrological Cellular-Automaton model (CATGraSS) of vegetation coexistence drivenby rainfall and solar radiation with downscaled future climate to examine the role of climate change on vegetationpatterns. In the model, each cell can hold a single plant type or can be bare soil. Plant competition is modeledexplicitly by keeping track of mortality and establishment of plants, both calculated probabilistically based on soilmoisture stress. Topographic influence on incoming shortwave radiation is treated explicitly, which leads to spatialvariations in potential evapotranspiration and resulting soil moisture and plant distribution. The influence of thesoil thickness on the vegetation distribution is also introduced. The model is calibrated first using a representationof the current climate as a forcing and comparing the vegetation obtained from the model with the actual vegetationthrough statistical techniques..The calibrated model is then forced with future climate scenarios generated using a stochastic downscaling techniquebased on the weather generator, AWE-GEN. This methodology allows for the downscaling of an ensembleof climate model outputs deriving the frequency distribution functions of factors of change for several statistics oftemperature and precipitation from outputs of General Circulation Models. The stochastic downscaling is carriedout using simulations of twelve General Circulation Models adopted in the IPCC 4AR, A1B emission scenario, forthe future periods of 2046-2065 and 2081-2100.A high sensitivity of the vegetation distribution to variation of rainfall and temperature has been observed. Thesimulations suggest that the observed vegetation pattern can exist only in the current climate while the changesin the future storm characteristics could lead to a dramatic reorganization of the plant composition based mainlyon the topography. Moreover the model analysis underscores the importance of solar irradiance in determiningvegetation composition over complex terrain.
Lingua originaleEnglish
Numero di pagine1
Stato di pubblicazionePublished - 2013


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