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Modeling the Influence of the Climate Change on the Vegetation Pattern Variation Using a Cellular Automata Model

Author(s): Domenico Caracciolo; Erkan Istanbulluoglu; Leonardo V. Noto

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Keywords: CA model; Climate change; Topography

Abstract: An ecohydrological Cellular-Automaton model (CATGra SS) of vegetation coexistence driven by solar radiation and rainfall has been used here to modeling the vegetation pattern at catchment scale. In the model, each cell can hold a single plant type or remain empty. Plant competition is modeled by keeping track of mortality and establishment of plants, both calculated probabilistically based on soil moisture stress. Spatially explicit treatment of solar radiation, and a lower limit to soil moisture storage imposed by bedrock depth lead to spatial organization in evapotranspiration, soil moisture, runoff, and plant type. The model is implemented in a small basin (1. 3 km2) in Sicily, Italy, where north-facing slopes are characterized by oak, and south-facing slopes by Indian fig opuntia and grasses. The model is forced first by a representation of the present climate, comparing the vegetation pattern obtained from the model with the actual vegetation pattern through statistical techniques in order to calibrate it. To understand how vegetation spatial patterns may change in the future as result of the climatic changes, the model has been then forced with future climate scenarios generated using a stochastic weather generator, the AWE-GEN. This generator allows for the downscaling of an ensemble of climate model outputs deriving the frequency distribution functions of factors of change for several statistics of the temperature and the precipitation from a multi-model ensemble of outputs of General Circulation Models (GCMs). The stochastic downscaling is carried out using the data of twelve GCMs adopted in the IPCC 4AR for the future scenarios2046-2065 and 2081-2100. A high sensitivity of the vegetation distribution to variation of rainfall and temperature has been observed. In particular the simulations suggest that the observed vegetation pattern can exist only in the current climate. The changes in the future storm characteristics could lead to a reorganization of the plant composition based mainly on the topography, characterized by loss of oak and expansion of grass. Rapid vegetation change could lead to soil erosion and changes in the biogeochemical processes in such steep mountainous terrains in the region.


Year: 2014

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