Download 529-exam 3

Biol 529 - Plant Ecology
20 December 2002
Exam 3
Instructions: Answer ONLY 4 of the following 9 questions. Each answer is equally weighted
at 25%. The questions are in 4 clusters. Answer only 1 question from each cluster. As usual,
read through the entire exam first, choose your questions, and then begin answering (please
number them with the number of the question). Enjoy and happy solstice holidays.
I. Answer only one question of #1 or #2:
1. Discuss how plants interact with each other. Give examples from competition for negative
interactions like competition and from positive interactions. Many ecologists claim that specific
outcomes depend on context. Take competition as an example and discuss the what ‘context’
means with respect to competition for soil resources between two plants species.
2. Herbivores can have a great impact on plants and their communities. Discuss how herbivores
can influence the structure of a plant community (structure = composition and abundance).
Among a number of theories about how plants respond to herbivores, 2 theories are current,
apparency theory and resource availability theory. Discuss one of these theories and provide
detail about the types of plant responses.
II. Answer only one question of #3 or #4:
3. The individualistic and organismic hypotheses concerning plant communities have had many
different reincarnations throughout their history. Whittaker claimed, for example, he couldn't
find distinct communities along gradients, while Daubenmire criticized him for not looking at
sites lacking disturbance and examining population structure to see what was going to happen.
In all these cases, arguments seem to depend upon assumptions of two features: degree of
stability and degree of integration of the community. a) choose either the individualistic or
organismic hypothesis; b) defend or criticize it; and c) elaborate on concepts of integration and
stability in your discussion.
4. All the new ways of examining plant communities, e.g., shifting mosaic, gap-phase or patch
dynamics, all call into question our historical view of dominance and climax. Bormann and
Likens in their Hubbard Brook experiment, for example, found that the tree species they
observed following disturbance could be placed into various syndromes combining a number of
life history characteristics, their two extremes being "exploitive" vs "conservative" species.
Similarly, Bazzaz worked with early successional herbaceous and woody species and determined
they distinguished readily into "early" vs "late" successional life history syndromes. a) how do
the "early" or "exploitive" species achieve dominance? b) how do the "late" or "conservative"
species achieve dominance? In your discussion, mention in what physiological and life historical
ways these two distinct syndromes differ. In other words, discuss the concepts of dominance and
climax with regard to these new interpretations of plant communities.
III. Answer only one question of #5 or #6:
5. Fire-prone habitats have always been problematic for community theorists. Clements, for
example referred to chaparral as an example of a disclimax or pseudoclimax, a community
prevented from reaching climax by fire. a) discuss the role of fire as a community level process;
b) explain what is meant by "regime"; c) compare and contrast it to other disturbances, is there a
fire regime that's distinct from a disturbance regime; d) do species in fire habitats fit the
categorizations of those in other disturbance regimes, e.g. conservative vs exploitive, as in the
Hubbard Brook deciduous forest.
6. Connell and Slatyer synthesized decades of work on successional mechanisms and came up
with three classes: facilitation, tolerance, and inhibition. Discuss these ideas and also some of
the criticisms of their work that Pickett and associates put forward. Pickett and associates also
provided a ‘framework’ for explaining succession. Explain their framework.
IV. Answer only one question of #7 or #8 or #9:
7. Invasive species are resulting in a world-wide homogenization of Earth's flora. Discuss some
ideas developing about invasives, what makes a good invasive, what characteristics of
communities prevent or permit invasion. How might invasives influence ecosystem processes?
Do invasive species fit into preexisting ecological concepts or theories, succession, patchdynamics, or will entirely new ones need to be developed (if existing, discuss; if new, then
why)?
8. One issue that confronts ecologists interested in management and conservation is the
appropriate application of ecological principles. What are the major issues for managers?
Discuss this by using two categories, general problems and constraints to management. For
managers of a natural reserve in an urban area, discuss what context means with respect to
problems and constraints. Give examples of an ecological principle and its application.
9. Cultural perspectives can shade our understanding of natural systems. Fully discuss this issue
by contrasting our historic ways of approaching natural systems ("balance of nature") with the
contemporary paradigm ("flux of nature"). Interpret examples from community theory and from
management (you could invent the management examples) that might fit into these contrasts.