Evidence that fungal pathogens inhibit recruitment of a shade-intolerant tree, white birch (Betula papyrifera), in understory habitats

This is the accepted manuscript of an article published by Springer Verlag.Evidence from tropical forests suggests understory habitats are associated with a high risk of disease, which may prevent the establishment of vulnerable tree species; in contrast, canopy gaps can act as refuges from these pathogens. However, few studies have investigated the impacts of pathogens on regeneration in temperate forests. To determine whether losses to fungi of seeds of Betula papyrifera, a light-loving species, varied between habitats that differed in their degree of openness, we applied fungicide to seeds buried in old fields, treefall gaps, and forest understory sites. We found that the application of fungicide significantly reduced losses in all habitats, relative to control values. This effect was habitat-dependent: the benefit of fungicide was greater in forest understory than in openings. This suggests that B. papyrifera is prevented from establishing in understory environments in part by its susceptibility to pathogen attack, and not solely because of a high light requirement.This is a publication of the Koffler Scientific Reserve at Jokers Hill. This research was supported by an NSERC PGS to DO'H-M and NSERC Research and Equipment Grants to PMK, with additional funding from Human Resources Development Canada. The National Tree Seed Centre (CFS, Fredericton NB) donated the seeds used in this study