Temporal and Spatial Patterns of Woody Plant Establishment in Michigan Old Fields

Abstract

We investigated temporal and spatial patterns of woody plant establishment in the first 7 y of succession in southwest Michigan old fields. From the 2nd to the 7th y following agricultural abandonment we conducted annual demographic surveys of woody plants and mapped all stems in six 10 × 20 m permanent grids to measure temporal and spatial patterns of woody stem emergence, mortality, density and species richness. Woody plant succession was characterized by increases in the emergence, density and richness of woody species over time and a shift from early dominance by wind-dispersed species to later dominance by bird-dispersed species. The increase in abundance of bird-dispersed stems reflects both clonal reproduction by the dominant bird-dispersed species, Rhus typhina, and establishment from seed by a variety of other bird-dispersed species. Wind and bird-dispersed species differed in spatial pattern within the grids. Wind-dispersed species were distributed at random and bird-dispersed species were aggregated. Aggregation of bird-dispersed species was due to clonal stem production by R. typhina and the concentration of stems of other bird-dispersed species beneath the canopy of Rhus clones. The results highlight the importance of dispersal mode in controlling both the rate of woody plant succession and the development of spatial structure in plant communities.