Feedback Between Ecological Interaction and Spatial Pattern in a Transitional Michigan Forest

Abstract

Ecology has traditionally thought of spatial patterns in one of two ways: (1) as a consequence of some underlying environmental heterogeneity and (2) as something to ignore in models to make them more tractable. But both of these views have changed, and in the last 20 years ecologists have increasingly considered the joint feedback that spatial pattern and ecological interactions can have on each other. Going in one direction the spatial pattern of organisms can greatly affect how their ecological interactions play out, and in the other direction local-scale ecological interactions can give rise to emergent, self-organized spatial patterns of organisms. This dissertation examines both directions of this feedback in the context of a mid-successional Michigan forest. The three dominant species in the understory of the forest exhibit strong nonrandom spatial patterning. Here we suggest that this spatial pattern emerges from biotic interactions -- the combined effect of local dispersal and Janzen-Connell, density-dependent seed and seedling mortality of two of these three species -- acting on an initial distribution of trees determined by the fire history of the area. That is ecological interactions give rise to spatial pattern, but this can only be understood in light of the history of the forest. We also suggest that this spatial pattern will affect how the succession of the forest; if the species were completely well-mixed the succession of the forest would take place differently. So we show that the spatial arrangement of organisms affects ecological processes.