Community Dynamics

The historical focus in community ecology on short-term experimental manipulations has resulted in an underappreciation of how dynamic communities and ecosystems actually are. We are interested in using long-term data to better understand how and why natural systems change. In particular, we are interested in how community structure and system-level properties respond to perturbations such as climate shifts, habitat change, and species extinctions or invasions.

example: responses to habitat change

As habitat has changed from grassland to desert scrub, the small mammals of the site have responded. Several species abundant early in the project have declined or gone locally extinct (Valone et al 1993) while others have colonized or increased, resulting in a major reorganization of the species composition (Ernest and Brown, 2001,Thibault et al 2004). However, despite major turnover many of the community-level properties (total abundance, total biomass, total energy use, species richness) have shown constrained variability

While community properties seem to be buffered against high variability in species composition, there are still long-term trends in many of those properties. Of particular interest is the decline in average body size at the site which seems to be driving a steady increase in total rodent abundance and a decline in total rodent biomass (White et al 2004). Despite changes in body size, abundance, and biomass, neither species richness nor community energy use has changed directionally. We think energy use is stable because resource availability is a constraint on the system—imposing zero-sum dynamics (sensu Hubbell 2001) on the community. Why species richness is also stable is an area of active research (e.g. Thibault et al 2004, Goheen et al 2005)