ABSTRACT
This chapter summarizes the mechanisms that maintain high plant species diversity in the system. It reviews the ecological theories that seek to explain community assembly and patterns of diversity at different spatial scales in species-rich plant communities. The chapter examines the empirical evidence addressing these theories. It focuses on field experiments where ecological processes have been manipulated in ways that help identify how plant community assembly occurs in natural or restored longleaf pine sites. Local- and regional-scale perspectives on community assembly can be organized along a continuum bounded at one extreme by niche-assembly theory and at the other extreme by dispersal-assembly theory, each embodying a large family of more detailed models and hypotheses. Processes occurring at fine spatial scales, such as spatial heterogeneity in fire, influence patterns of community assembly. Species richness attributed mechanisms of species co-occurrence to the elimination of woody competition and litter by fire and to phenological differences in biomass production by small- and large-stature species.
