I am interested in understanding how spatial patterns form in ecological systems. Historically such patterns were assumed to be the result of some underlying environmental heterogeneity. But it is well known that non-random pattern can form through the interaction of particles in a homogenous environment — self-organized spatial pattern formation. I want examine to what extend this process happens in ecological systems, and when it does how these self-organized pattern formation processes interact with underlying environmental heterogeneity.
I do this work from a theoretical perspective, but also in an empirical system. In 2003 a 12-ha plot of forest at the E.S. George Reserve was censused, with all trees larger than 10-cm girth at breast height identified, measured and spatially referenced. The forest was re-censused in 2008, and an additional 8 hectares were added. The forest, like many in northeastern North America, is undergoing a drastic shift in composition. It has an oak-hickory canopy but few oaks and hickory in the understory. And as they die these canopy trees die there are not enough in the understory to replace them. Instead the future canopy will be increasingly made up of maples and cherries.
The understory of the forest is strikingly spatially patterned, with red maples, black cherry and witch hazel — which make up 75% of the subcanopy — forming a tight jig-jaw-like mosaic. My research seeks to understand how this mosaic formed, and how long it will persist. Specifically will it persist into the time when the red maple and black cherry take over the canopy. If you would like a copy of this data set please email me, email@example.com.
Z. Brym, D. Allen, and I. Ibáñez. 2014. Community control on growth and survival of an exotic shrub. Biological Invasions: In press.
D. Jackson, D. Allen, I. Perfecto, and J. Vandermeer. 2014. Self-organization of background habitat determines the nature of population spatial structure. Oikos. In press
A. Belasen, E. Burkett, A. Injaian, K. Li, D. Allen, and I. Perfecto. 2013. Effect of sub-canopy on habitat selection in the blue-spotted salamander (Ambystoma laterale–jeffersonianum unisexual complex). Copeia 2013(2): 254–261. PDF
J. Sha, D. Allen, H. Liere, I. Perfecto, and J. Vandermeer. 2012. Mutualisms and population regulation: mechanism matters. PLoS ONE 7(8): e43510. (access)
S. Yitbarek, J. Vandermeer, and D. Allen. 2011. The combined effects of exogenous and endogenous variability on the spatial distribution of ant communities in a forested ecosystem (Hymenoptera: Formicidae). Environmental Entomology 40: 1067–1073. PDF
Z. Brym, J. Lake, D. Allen, and A. Ostling. 2011. Plant functional traits suggest novel ecological strategy for an invasive shrub in an understorey woody plant community. Journal of Applied Ecology 48: 1098–1106. PDF
D. Allen, J. Vandermeer, and I. Perfecto. 2009. When are habitat patches really islands? Forest Ecology and Management 258: 2033–2036. PDF
D. Allen and J. Vandermeer. Janzen-Connell in the temperate zone: contribution to the formation of spatial pattern in the subcanopy of a successional forest. In prep.