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Harvard Forest Symposium Abstract 2012

  • Title: Pathogen effects in forest tree diversity
  • Primary Author: Maria Benitez (Duke University)
  • Additional Authors: James Clark (Duke University); Michelle Hersh (Cary Institute of Ecosystem Studies); Rytas Vilgalys (Duke University)
  • Abstract:

    Recruitment of first-year seedlings is dependent on multiple factors, including the intensity of seed rain and negative-density dependent regulation. According to the Janzen-Connell hypothesis, the distance from adult trees and the density of conspecifics can influence recruitment of new seedlings, and these negative feedbacks are associated with host-specific pathogen pressure. However, the identity and degree of host-specificity of fungal pathogens contributing to seedling mortality in temperate hardwood forests, such as Harvard Forest, remains unknown. In this study we aim to understand the role of fungal pathogen in influencing seedling recruitment rates. Seedling germination and mortality is being evaluated on first-year seedlings planted at two sites, in the Simes and Slab City tracts. To study fungal communities, healthy and diseased seedlings are sampled from the field and processed for pure-culture isolation and DNA extraction. In 2011, seeds of two species were planted at two density levels along a soil moisture gradient. Acer saccharum germination ranged between 0 – 30% and mortality was almost 100%. For Quercus rubra, survival rates were higher overall (ranging between 30-100%) and differed between sites. Culture-based and culture-independent analyses of fungal communities from healthy and diseased seedlings are currently underway. In 2012, seeds of five plant species were planted at locations considering distance to parent tree treatments to evaluate mortality and impact of fungal infection within the context of the Janzen-Connell hypothesis. Equivalent experiments are being conducted at hardwood sites from Duke Forest (NC). By incorporating seedling demography and fungal community data, we aim to understand fungal pathogen effects on plant community dynamics and diversity.

  • Research Category: Biodiversity Studies
    Invasive Plants, Pests & Pathogens
    Physiological Ecology, Population Dynamics, and Species Interactions