Draft Plan for FEScUE Seminar (last 4 weeks) and Summer – 3/17/08
Research Area: Changes in food web structure affect ecosystem function, but little is
known about what mediates this structure-function relationship. Using simulation
approaches, we propose investigating how spatially localized interactions constrain
resilient food web structure (i.e., structure that minimizes the impact of disturbance), and
hence control the structure-function relationship through two types of feedback. First,
correlations between the feeding preferences and movements of individual species link
food webs and the spatial distribution of organisms. The spatial distribution of organisms
may affect the outcome of disturbance to food webs and feed back on the structurefunction relationship. Second, individuals move nutrients around the landscape, thus
individual movement affects the degree of local control on nutrient recycling and the rate
and spatial distribution of resources. Through these two feedbacks, spatially localized
interactions can scale up to affect the level and spatial distribution of productivity at the
whole system scale. An optimum in food web resilience occurs independently at
intermediate levels of productivity (Moore et al. 1993) and with intermediate levels of
spatial aggregation (Webb and Levin 2005). These system properties are connected via
the underlying local interactions, suggesting that the level and distribution of productivity
in combination may determine underlying constraints on resilient food web structure.
We also propose to expand these ideas to include predator-prey interactions (Rosenzweig
1971) that are somewhat biologically similar to the microbe-detritus interactions
described above, but have been incorporated into models with fundamentally different
mathematical properties from those used to describe microbe-detritus interactions.
This research area is quite broad-based. We propose providing FEScUE students with
the basic biological background information and some basic simulation tools. FEScUE
students will then drive the specific research questions that will be addressed.
End-of-Semester Plan: During the last four weeks of the semester, students will read,
discuss, and rederive the results from Rosenzweig 1971 and Moore et al. 1993. They will
also see a presentation and discussion with C. Webb on the implications of spatial
patterns for disturbance propagation (Webb unpublished). We have asked Dale
Lockwood to facilitate the discussions of Rosenzweig 1971 and Moore et al. 1993 while
C. Webb is on maternity leave (Note: I do not yet have confirmation from Dale). C.
Webb and J. Moore will also meet with students to discuss the integration of this material
to form the research area described above.
Summer Plan: Towards the end of the formal seminar with D. Cooley, we hope there
will be some outlining of Poisson birth-death processes. The summer research plan will
begin by building on this information to help students develop generic tools for
simulation of ecological problems. The plan is for Don’s graduate student to help the
students develop code for the following two problems. First, students will learn to
implement a Poisson birth-death process and develop general code for doing so. Second,
students will learn to implement a spatial birth-death process and develop general code
for doing so. Finally, students will learn partial validation techniques for their
simulations such as comparing results for random movement processes in the spatial
implementations to the Poisson birth-death simulation and to ode models.
Long-range Plan: After students have generated general code for Poisson birth-death
processes and spatial simulations, they can modify the code to investigate specific
problems related to the research area that was introduced at the end-of-semester. We can
begin this research at whatever point in the summer they have completed the basic
simulation toolkit that they will need and continue into the school year.
References:
Moore, J.C., P.C. de Ruiter, and H.W. Hunt. 1993. Influence of productivity on the
stability of real and model ecosystems. Science 261: 906-908.
Rosenzweig, M. 1971. Paradox of enrichment: Destablization of exploitation
ecosystems in ecological time. Science 171: 385-387.
Webb, C.T. and S.A. Levin. 2005. Cross-system perspectives on the ecology and
evolution of resilience. In: Robust Design: A Repertoire of Biological, Ecological,
and Engineering Case Studies. E. Jen (Ed.). Oxford University Press. pp. 151-172.