Simulating the effects of a climate-change scenario on the geographical range and activity of forest-pathogenic fungi

The aim of the present study was to explore possible effects of climate change on the geographic range or local impact of several forest-pathogenic fungi. To this aim, (i) the parameters of species' responses to climatic variables were determined, in two types of models (specific statistical models and the generic model CLIMEX); (ii) these models were used to make simulations under a future climatic scenario based on a general circulation model of climate, which was regionalized over France. A range of pathogens commonly reported in Europe were studied: Melampsora laricipopulina, Melampsora allii-populina, and Melampsora medusae, causal agents of poplar rust; Mycosphaerella pini, an agent of red-band disease of pines; Melampsora pinitorqua, an agent of pine-twisting rust; Cryphonectria parasitica, an agent of chestnut blight; Phytophthora cinnamomi, causal agent of ink disease on European chestnut (Castanea sativa) and oaks; and Sphaeropsis sapinea and Biscogniauxia mediterranea, which are opportunistic pathogens (cortical endophytes) on pines and oaks, respectively. The predicted warming would be favourable to most of the studied species, especially those for which winter survival is a limiting factor linked to low temperatures (P. cinnamomi and Melampsora medusae). For species such as Mycosphaerella pini, the favourable effect of warming would be counterbalanced by the negative effect of a decrease in summer rainfall, leading to a stable or decreased impact of these pathogens by the end of the century. Conversely, B. mediterranea and S. sapinea, which are favoured by water stress, should have an increased impact. Interest and limitations of the different models were discussed. Some implications of the projected changes in forest phytosanitary landscape were presented in terms of research and management issues.