Center on Global Change Seminar Series - Hormoz BassiriRad, University of Illinois at Chicago, "Chronic Atmospheric Nitrogen Deposition: Implications for Biogeochemistry & Plant Diversity in Temperate Forests"

Two oak/maple dominated forest stands nearby the Chicago metropolitan area were studied for seven years to assess the impacts of chronic atmospheric N deposition. For the past several decades, these forests have been exposed to some of the highest N deposition rates for the continental US and represent a low and high end of a deposition gradient. Data from here and those pre-dating this study indicate a gradual shift in species composition in favor of maple as opposed to oak with little sign of a forest decline. The species differential responses to atmospheric N deposition is most likely linked to the seedling recruitment stage and it is associated with a dramatic shift in the relative abundance of soil amino acid to inorganic N composition. The species composition shift also coincides with a significant reduction in colonization of oak roots by ectomycorrhizal fungi. Most significantly, the study found that the ectomycorrhizal sheath (mantle) forms a chief component of soil N compartment (more than 20% of the plant fungal complex) which is also the most sensitive pool in response to atmospheric N input. The study provides additional conceptual and mechanistic perspectives to those of John Aber and colleagues in understanding forest responses to chronic N.BassiriRad's research focuses on belowground activities, root biology, water relations, gas exchange and nutrient cycling. Please see More Information for a detailed abstract and speaker bio. Refreshments provided.