Organismal and Population Biology: Principals underlying ecological succession Sam Rossman and Kateri Salk Paper: Reynolds, H. L., Packer, A., Bever, J. D., and Clay, K. (2003). Grassroots ecology: plantmicrobe-soil interactions as drivers of plant community structure and dynamics. Ecology, 84(9), 2281–2291. Supporting Materials Lichter, J. (1998). Succession and forest development on coastal Lake Michigan sand dunes. Ecological Monographs, 68(4), 487-510. Van der Putten, W.H., Van Dijk, C., and Peters, B.A.M. (1993). Plant-specific soil-borne diseases contribute to succession in foredune vegetation. Nature, 362, 53-56. Common naïve (mis)conceptions: Plant processes alone dominate succession Land becomes fertile only through human-mediated activities like fertilizer application Pathogens are “bad” for an ecosystem The more nutrients in an ecosystem the healthier it is Certain stages of succession are “better” than others The best ecosystems are those that remain in a late-successional community indefinitely Student learning objectives: Comprehend the relationships between disturbance, plant-microbe mutualisms, soil nutrients, and species richness Analyze how positive and negative feedbacks regulate ecological succession Predict patterns of ecological succession using environmental data and ecological theory Metacognitive pre/post class homework: Pre-class: Read Reynolds et al. 2003 and complete the following assignment on carbonless paper: 1. Define and provide an example of each of the concepts below. These topics are addressed in Reynolds et al. 2003. Feel free to use any internet resources to fill in gaps in knowledge. Succession Disturbance Mutualistic plant-microbe interaction Pathogenic plant-microbe interaction Mycorrhizae Positive feedback Negative feedback 2. Find an example online of an ecosystem undergoing succession. Your example should include images of the ecosystem in an early successional stage and a late successional stage (stages in between can be included but are not required). Print two copies (one for each copy of your carbonless paper) or draw on carbonless paper. Create a list of the living and non-living components of the ecosystem that change from one stage to the next. Post-class (or end of class): Based on class activities and the model you completed for the dune ecosystem, evaluate the list you generated in #2. Did you leave out any important components in the ecosystem that change as succession progresses? Additionally, comment on the interaction of multicellular organisms, microbes, and abiotic components in your ecosystem. Write your evaluation in the form of a reflection paragraph on carbonless paper. In-class Assessments: Introduction Ask students to share examples of successional ecosystems they chose for their homework. Hopefully they will have chosen a variety of ecosystems. If not, we will share a few examples of ecosystems they might not have thought of. The conclusion to draw from this is that succession occurs almost everywhere and that disturbance is a key player. Clicker questions to assess comprehension of concepts in Reynolds et al. 2003 and address potential naïve conceptions of students regarding succession 1. What is the take-home message from figure 1 in Reynolds et al. 2003? a. Soil cycling of N and P doesn’t matter to plants; they will take up any form of nutrient that is available b. Fertilizers must be applied to soils for plants to get the nutrition they need c. Some plants require N for growth, and others require P for growth d. Plants rely on a variety of N and P transformations to acquire the unique set of nutrients they need 2. In figure 1 in Reynolds et al. 2003, which organisms are responsible for the cycling (transformation) of N and P? a. Plants b. Microbes (bacteria, archaea, fungi) c. Plants and microbes d. N and P cycling happens abiotically (without help from organisms) 3. An infectious fungus commonly referred to as root rot often infects and kills plant tissue, facilitating nematode herbivory of the plant. Nematodes in turn, carry the fungi to new plants. Which of the following best describes the relationship between root rot and nematodes? a. b. c. d. Negative feedback Secondary succession Mutualism Disturbance 4. Which of these is NOT a characteristic of an environment where positive feedback is likely? a. High latitude b. Plant-microbe mutualisms common c. Species-specific soil pathogens common d. Early successional stage Modeling exercise* Use the figures provided from Lichter 1998 to construct a model depicting a young, intermediate and mature dune ecosystem that highlights the processes and organisms that are important for succession. Include the parameters measured in the figures and potential interactions with microbial life. Document (with brackets, shading, etc.) the stages where positive and negative feedback could be in play. Work in groups of four and draw your models on carbonless paper. Think-Pair-Share exercise* Analyze how the Van der Putten figures (provided via powerpoint) illustrate plant-microbe interactions. Make a hypothesis about the nature of the plant-microbe relationship based on the evidence given in the figures. Additionally, determine whether the figure illustrates a positive or negative feedback for plant growth and colonization. Construct another figure that depicts how plant production would differ if the opposite feedback were in play. *Before the modeling and think-pair-share exercises, we will give a little background on dune succession (likely with photos) and on the two separate studies.