Date of Graduation
Eberly College of Arts and Sciences
Geology and Geography
Brenden E. McNeil
Amy E. Hessl
William T. Peterjohn
Richard B. Thomas
Atmospheric deposition of pollutants and nutrients can have a range of effects on aquatic and terrestrial ecosystems. Despite its ecological importance, it remains a challenge to model patterns of deposition across complex terrain and also to assess how forest ecosystems are reacting to chronic inputs of atmospheric deposition. I measured the lead (Pb) content of forest soils adjacent to atmospheric deposition monitoring stations throughout the central Appalachian Mountains to examine how well patterns of soil Pb relate to regional patterns of inorganic nitrogen (N) deposition. While I found no significant relationship between organic soil Pb content and N deposition, I did find a strong positive relationship between mineral soil Pb content and N deposition, (R2=0.68, p=0.08). These results indicate that mineral horizon soil Pb is a potentially useful index of pollutant deposition in this region. Furthermore, the measurement of mineral soil Pb provides a practical, surrogate measure of depositional patterns for ecologists interested in observing the effects of atmospheric deposition on ecosystem function. I also examined the effects of acid deposition on tree growth by sampling three tree species (Picea rubens, Liriodendron tulipifera, and Betula alleghaniensis) along spatial gradients of deposition within the eastern United States. By studying tree-rings along the gradient, I was able to examine the inherently long-term and cumulative effects of deposition on tree growth and how this response changed through time. While a limited sample size and stand dynamics overwhelmed the ability to detect any growth response within the Liriodendron or Betula study sites, I did discover a strong negative relationship between the deposition gradient and Picea growth in the central Appalachian Mountains (R2=0.89, p=0.05). Interestingly, the strength of the relationship within our Picea dataset changed through time, in parallel with known temporal patterns of deposition in the region. I found that the use of tree-ring analyses in carefully selected plots along environmental gradients provides the unique opportunity to not only assess growth responses to spatially-varying patterns of environmental change, but to also characterize how forests are reacting to slow cumulative changes through time. The promising results seen in this study should be expanded upon in the future.
Breslow, Bradley P., "Development of soil lead and tree-ring methods for characterizing atmospheric deposition gradients and subsequent tree growth responses" (2011). Graduate Theses, Dissertations, and Problem Reports. 665.