Influence of stand age and physical environment on the herb composition of second-growth forest, Strouds Run, Ohio, USA
Historical land use in eastern North America and much of Europe has created a mosaic of successional forest stands of widely varying age. An estimate of the rate of successional community development would allow the conservation value of individual stands to be assessed. We estimate the rate of herb community development in secondary forests in our region, and the extent to which physical gradients determine herb distributions. Location
Second-growth forest in the Appalachian Oak section of the Central Hardwoods Region, southeastern Ohio, USA. Methods
Thirty-five plots were surveyed in old (82–193 years) and young (35–40 years since pasture) deciduous forest stands and pine plantations. In each plot, herb species cover and environmental factors were measured. Results
Herb community composition was clearly distinguishable between oak-dominated upland sites and mixed mesophytic stands in moist ravines. In both community types, young stands were compositionally distinct from old stands. Species lacking obvious seed dispersal mechanisms were disproportionately uncommon in young stands, implying dispersal limitation in the process of recolonization. Among old stands, distributions of many species showed significant regressions on the environmental variables, whereas few showed significance in young stands. Species with weak dispersal tended to be more frequently linked to environmental gradients in old stands than in young stands. Main conclusions
Early arriving forest species appear to assort rapidly along physical gradients, defining communities early in the successional trajectory. The re-assembly of the full forest community continues over a longer period as individual species assort on environmental gradients at rates determined by their dispersal abilities. Thus, long-established stands show more spatial variation than successional stands, and offer greater opportunities for conservation of the forest community.