Ecological Modelling 360 (2017) 399–409 Contents lists available at ScienceDirect Ecological Modelling journa l h om epa ge: www.elsevier.com/locate/ecolmodel The importance of interspecific competition in the actual and future distributions of plant species assessed by a 2-D grid agent modelling Marcello Vitale a,∗ , Silvia Lorenzetti a , Fabio Francesconi a , Fabio Attorre a , Mario Di Traglia b a Department of Environmental Biology,Sapienza University of Rome - Piazzale Aldo Moro, 5–Rome, Italy b Department of Public Health and Infectious Diseases,Sapienza University of Rome - Piazzale Aldo Moro, 5–Rome, Italy a r t i c l e i n f o Article history: Received 27 February 2017 Received in revised form 24 July 2017 Accepted 25 July 2017 Available online 5 August 2017 Keywords: 2D cellular automata Climate change Competitive asymmetry Mixed forest Plant distribution a b s t r a c t Currently, potential distribution of plant species is represented by different uses of presence/absence indicators or by density-dominance-based ones such as the Importance Value (I.V.), and their geographi- cal representation is based on statistical models (Random forest model, General Regression Models etc.) relating these indicators with climate and physical features of a given territory. Here, we have built an integrated model which is able to link climate, physical features of territory and inter-specific competi- tion at aiming to simulate potential distribution of eight plant species (Quercus cerris, Quercus pubescens, Fraxinus ornus, Fraxinus excelsior, Acer campestre, Acer obtusatum, Ostrya carpinifolia and Carpinus betulus) either at actual climate conditions or future ones (B1 and A2 climatic scenarios; IPCC, 2013). The inte- grated model is based on innovative methodological approach, which combined statistical tools (Principal Component Analyses and Discretization) and two-dimensional grid based model to consider the inter- active effects of climate and inter-specific competition on plant species distribution. The study case was given by geographical spatialisation of the I.V. for each considered plant species, in the overall Italian ter- ritory. The simulations had always occurred by taking into consideration both expected climate change and inter-specific competition under highly complexity terrains. The results substantially differed from other studies that used only environmental predictors for estimating potential plant distributions. Vari- ations in the I.V. distribution seemed to be due to variations of relative competitive abilities of plants, reducing both local extinctions of some species in Southern and Central Italy and migration toward North. Furthermore, our simulations suggested that under pressure of climate change the competitive ability of plant species will be likely affected by reducing the effects of competitive asymmetry. © 2017 Elsevier B.V. All rights reserved. 1. Introduction The global warming is ongoing from the 20th century and it is showing a worrying increase of mean global temperature and not uniform distribution of rainfalls at regional level (Kirtman et al., 2013), causing thus a severe threaten for biodiversity of animal and plant species (Settele et al., 2014). Warming trend is bound to increase during the 21st century; regional differences will be enhanced for Europe, with severe impacts on Mediterranean basin (Lindner et al., 2010). The major effects observed on vegetation have been ascribed to variations in distribution and phenology: expansion of thermophilous species and reduction of micro ther- ∗ Corresponding author. E-mail addresses: marcello.vitale@uniroma1.it (M. Vitale), fabio.francesconi@uniroma1.it (F. Francesconi), fabio.attorre@uniroma1.it (F. Attorre), mario.ditraglia@uniroma1.it (M. Di Traglia). mal ones, species’ shift toward higher altitude and latitude, earlier occurring of spring events (Kannan and James, 2009; Parmesan and Yohe, 2003; Fitter and Fitter, 2002). It is worth to note that climatic, physical and physiological parameters are all occurring at the same time and space, and they are reciprocally interacting each other, creating favourable conditions, or not, to the plant species’ shift, affecting thus species-specific distribution. The occurring new cli- matic conditions can be tolerated by plant species, or they can move into ecologically suitable areas matching their functional needs (Attorre et al., 2011; Benito Garzón et al., 2008). Furthermore, global warming can affect the competitive abilities of plant species in dif- ferent ways. It can reduce the competitive asymmetry, that is the growth of a potential dominant species can be limited in less eli- gible environments for primary production at increasing of aridity (Fargione and Tilmann, 2002; Keddy et al., 2000). Changes in the resource availability and in plant species distribution can thus mod- ify inter-specific competition effects as consequence of the climate change (Fargione and Tilman, 2002; Schwinning and Weiner, 1998; http://dx.doi.org/10.1016/j.ecolmodel.2017.07.027 0304-3800/© 2017 Elsevier B.V. All rights reserved.