Pathogen impacts

Pathogen Impacts on Forest Biodiversity in the Face of Climate Change

Project PIs:

Postdoctoral Associate: Maria Soledad Benitez

Funding: National Science Foundation


Fungal pathogens may control biodiversity of forest trees through selective mortality of species that would otherwise threaten less competitive species. Climate warming may increase the amount and severity of disease as these pathogens increasingly survive mild winters, their reproductive rates increase, and plant defenses suffer from drought and temperature stress. We are evaluating the extent to which pathogens regulate tree seedling health, the fungi involved, and their effects on tree growth and survival. We are studying how those interactions are affected by the temperature changes predicted for mid-century.

In a warming experiment where tree seedlings are exposed to soil and air temperature increases of 3°C to 5°C in NC and MA, the study allows us to quantify how temperatures affect their hosts when temperatures increase, depending on the competition they simultaneously experience from other tree species. Once seedlings emerge, germination, survival, disease symptoms, and growth will be monitored. Pathogenic fungi and oomycetes residing on both seeds and seedlings will be identified using a combination of culture and DNA sequence-based methods. The effects of warming on pathogen incidence, infection, and seedling demography will be assessed using models that account for the combination of temperature, pathogens, and competition with other trees. By incorporating different sources of data into the analyses, this research will provide insight into the basic biology of forest risk as the natural enemies of the capacity of trees to defend themselves change under a warmer climate.

An improved understanding of the diversity and composition of populations of plant pathogens and environmental factors can both enhance current management practices and inform models of future tree distributions. The study aims to identify species at risk from pathogen pressures and under which specific conditions.

Recent Publications:

  • Ponce, S.B., M. Hersh, R. Vilgalys, and J.S. Clark. 2013. Pathogen regulation of plant diversity via effective specialization. Trends in Ecology and Evolution, in press.
  • Hersh, M.H., R. Vilgalys, and J.S. Clark. In press. Evaluating the impacts of multiple generalist fungal pathogens on temperate tree seedling survival. Ecology. [doi:10.1890/11-0598.1]
  • Clark, J.S., D.M. Bell, M.H. Hersh, and L. Nichols. 2011. Climate change vulnerability of forest biodiversity: climate and resource tracking of demographic rates. Global Change Biology 17:1834-1839.
  • Clark, J.S. and M. H. Hersh. 2009. Inference when multiple pathogens affect multiple hosts: Bayesian model selection. Bayesian Analysis 4:337-366, DOI:10.1214/09-BA413.