Canopy Thinning and Death Impacts Growth and Reproduction of Isotria medeoloides – a Federally Threatened orchid

Dennis Whigham, Smithsonian Environmental Research Center

Long-term monitoring of Isotria medeoloides at two sites in Virginia have been combined with observations from an understory thinning experiment at one site and death of a large canopy tree at a second site. New plants emerged at both sites following increased light levels and flowering and fruit production increased. Growth was related to canopy openness. The enormous increase in the population at the site where the canopy tree died has lead to the suggestion of the ‘fungal abundance hypothesis’ as an approach to management of the species.