Research :: Soil-Borne Pathogens and Forest Dynamics
Summary
Soil-borne pathogens make play an important role in maintaining diversity in forest communities. Through the process of distance- and/or density-dependent seedling mortality (ala the Janzen-Connell hypothesis), soil-borne pathogens can prevent the establishment of conspecific seedlings near adult trees. This creates a "dead zone" where heterospecific seedlings can recruit, enhancing local diversity. While originally conceived as a mechanism explaining high levels of tropical forest diversity, the Janzen-Connell hypothesis is best illustrated by black cherry (Prunus serotina) in southern Indiana forests.
This work is in collaboration with recent graduate student and post-docs Alissa Packer (now at Susquehanna University) and Kurt Reinhart (now at USDA-ARS Montana). Black cherry is attacked by soil borne pathogens (Pythium soil) that inhibit seedling establishment in the vicinity of adult trees, in accordance with the Janzen Connell hypothesis, and reduce growth of survivors. Recent results have demonstrated that negative feedback between black cherry and its soil community develops very rapidly (in a few weeks) in local communities. We are examining how negative feedback changes with successional age of the community, assessing the host specificity of Pythium soil causing damping off in black cherry, and evaluating whether other temperate tree soil are similarly affected by soil-borne pathogens.
An offshoot of this work is testing the idea that black cherry has become highly invasive in Europe because it has escaped its natural enemies, including soil-borne Pythium soil. Greenhouse and growth chamber experiments confirm that European Pythium soil are less virulent on black cherry, and field measurements indicate that black cherry saplings and adults are much more closely spaced compared to Midwestern forests.
NSF grant abstract for black cherry project (PDF)
Representative Publications on Soil-Borne Pathogens and Forest Dynamics (Download PDF)
Representative Photos
