General Discussion Summary
Our discussion on 2/12/13 pertained to alternative stable states. Two case studies were first presented: Heffernan (2008) on desert stream wetlands and Lansing (2012) on alternate stable states in a social-ecological system. We moved to a general discussion of key alternative stable state concepts to help us talk from the same understanding of definitions. A key distinction in considering alternative stable states relates to threshold responses versus bifurcation responses. We talked in pairs about how to define a stable equilibrium and how we could distinguish between non-equilibrium dynamics and resilient alternative stable states of systems. The end of class offered discussion of the various papers commenting on the Didham & Watts (2005) thesis that abiotic environments lead to higher incidences of stable state dynamics.
Didham and Watts (2005) Paper
The thesis of the D&W paper was that abiotic environments lead to higher incidences of stable state dynamics. The flow of ideas is: 1) Propagule limitation, 2) trait underdispersion, 3) stochastic priority effects, and 4) existence of alternative stable states (could be driven by competition or feedback on abiotic environment). D&W claim trait underdispersion happens in strongly stressed/abiotic environments due to an abiotic filter, not competitive interactions. Many of the papers responding to D&W focused on competition as an important structuring force for the communities. Priority effects are generally agreed to cause the alternative stable states, but this viewpoint is limited. Priority effects might not be the only causal factor for alternative stable states.