Organismal and Population Biology: Principals underlying

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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.
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