To quantify the full array of potential outcomes I have established six study sites along a latitudinal gradient in Michigan, at the University of Michigan Biological Station (UMBS), in Manistee National Forest, and at the Edwin. S. George Reserve (ESGR). Next year I hope to add two additional sites in the UP. Michigan is an ideal location for studying shifts in plant ranges as it encompasses the northern range limits of many common temperate forest species. Furthermore, my advisor, Dr. Inés Ibáñez, is conducting related experiments at some of these sites, giving me access to baseline data and established research infrastructure.
EXPERIMENTAL DESIGN: First, I will germinate and raise seedlings in the research greenhouses at the Matthaei Botanical Gardens. At each site I will establish multiple new plots along light and moisture gradients to complement existing plots from my last two summers of fieldwork. At each plot I will plant 5 species of plants under three treatments. These include: herbivore exclosures, opened exclosures which allow herbivore access but control for the effects of the exclosures upon the plants, and lastly seedlings without exclosures. I will plant 5 replicates of each treatment per plot, for a total of 1650 seedlings. During the growing season I will regularly monitor seedling mortality, herbivory on each individual leaf, and pathogen activity. I will also survey the insect community at each site and take samples of the pathogens which are affecting the seedlings.
At each site I will also monitor light conditions, temperature, soil chemistry, and soil moisture. The spatial and temporal variability of the environmental data will allow me to evaluate the response of each species to a temperature and soil moisture gradient that includes conditions predicted for future decades. I will analyze the data with hierarchical Bayesian modeling. This will allow me to incorporate several sources of information, including seedling data, herbivory, pathogen activity, environmental variables and site characteristics, and will allow me to determine how important each factor is to seedling recruitment in current and future climate conditions. Furthermore, it will allow me to take in to account the uncertainty associated with the data and the recruitment process (Ibáñez et al. 2009). Seeds and seedlings will also be planted at each site for an additional summer in order to sample the inherent annual stochastic variation in seed germination and seedling recruitment.
National Science Foundation