Susceptibility to Fungal Pathogens of Forests Differing in Tree Diversity

Abstract

In the overall functioning of forest ecosystems, both tree diversity and tree diseases matter, although their effects at times may be confounded by other factors (Barthod 1994; Malmström and Raffa 2000; Heil 2001; Naeem 2002b). The effects of biodiversity on ecosystems vary strongly amongst the systems studied, and evidence is scarce, owing to the relative lack of studies in forests (Schläpfer and Schmid 1999). Environmental change, either involving single abiotic factors (Pfisterer and Schmid 2002), or when combined with pathogen and host introductions, may result in unprecedented effects (Lonsdale and Gibbs 1995; Coakley et al. 1999;Ayres and Lombardero 2000). It is still an open question to what extent data from artificial cropping systems are relevant to natural plant communities. Likewise, the relative importance of abiotic perturbations, animal predators, and herbivores versus pathogens has to be further investigated. Progress will come from species performance studies in existing forest ecosystems, combinatorial biodiversity experiments, and evolutionary epidemiology. A thorough understanding of the interrelations between diversity and disease in forest pathosystems is an essential prerequisite for sustainable ecosystem management. The role of pathogens in influencing tree diversity of forests, as well as the function of tree diversity on disease impact, undoubtedly deserve further research, both empirical and through modeling, and not only by plant pathologists.