Potential risk of occurrence of Phytophthora alni in forests of the Czech Republic
Dušan Romportl, Eva Chumanová, Ludmila Havrdová, Vítězslava Pešková, and Karel Černý
Phytophthora alni is an invasive organism that causes root and collar rot in alders, which significantly damages the forest and riparian vegetation of alder trees in Central and Western Europe. In the Czech Republic, this pathogen was first confirmed in 2001, and since then it has been gradually spreading from the west to the east. Here, we applied a model of potential distribution that estimates the level and spatial variability of the pathogen occurrence and spread risk for Czech Republic forests to target the early detection and control the further invasion of P. alni in this region. Our predictions are based on a rigorous statistical analysis of data obtained from field survey as well as available geodatabases. We used two sets of predictor variables describing (i) the forest stands and (ii) neighbourhood of the stands, and generalized linear modelling with forward stepwise selection of predictors. The results of statistical analysis showed the significant effect of the area of the forest stand, forest vegetation zone, presence of watercourse and area of alder stands in the neighbourhood on the probability of occurrence of P. alni in the study region. The map derived based on the final model shows the potential risk of occurrence and impact of P. alni in forests of the Czech Republic as classified on a five-point scale ranging from very low risk for alder stands with a low level of likely invasion to very sensitive alder stands with high probability of pathogen occurrence and high levels of damage. This is a unique output not only for the Czech Republic but also throughout Europe.