Klara Dolos

Site suitability for tree species: Is there a positive relation between a tree species’ occurrence and its growth?

In order to preserve forest ecosystem services under climate change, site suitability for tree species has to be re-assessed and management strategies have to be developed to adapt species composition. Thereby, it is reasonable to consider information on both site suitability estimations based on current species distribution and also stand productivity determined by tree growth. Currently, models for species distribution (SDMs) and tree growth are used to investigate the response of tree species to climate. However, both approaches were only applied separately so far. In this study, SDMs and growth models for Picea abies, Fagus sylvatica, Abies alba and Pinus sylvestris were calculated based on the German national forest inventories. We asked whether there is a positive relation between a tree species’ occurrence and its growth and what can be learned by their joint interpretation. The two approaches resulted in different patterns with respect to the considered environmental variables. Tree growth and occurrence probabilities were not positively correlated. This may be explained by the influence of forest pathogens and competition on species distribution by means of an increase in mortality. We concluded that the consideration of demographic processes as drivers of species distribution improves the reliability of estimates for site suitability and additionally provides information on productivity.