THE EFFECT OF LOGGING ON SPECIES DIVERSITY AND EXOTIC SPECIES PRESENCE IN TEMPERATE HARDWOOD FOREST

Abstract

Anthropogenic disturbance is linked to loss of global plant biodiversity through several processes, including habitat destruction and displacement by introduced species. I examined the relationship between disturbance severity, changes in plant diversity, and exotic species invasion in a central Maryland secondary hardwood forest in which a silviculture demonstration project had been established six years previously. I compared total species richness, exotic species richness and percentage of exotic species in plots subject to five different logging regimes (clearcut, seed tree, shelterwood, single-tree selection and group selection) and uncut control plots, at one and six years after cutting. I found significantly greater species richness in even-aged logged plots than in unlogged plots, but no difference between logged and unlogged plots in uneven-aged stands. There was a significant increase in total species, exotic species and percentage exotic species along the increasing disturbance gradient from group selection to clearcut, but no significant difference in any of the dependent variables between logged plots cut in 1991 and 1997. There was no statistically significant evidence for the intermediate disturbance hypothesis. The results of the study can be explained largely by the density effect on diversity; other explanations are discussed. Disagreement between these findings and the work of other researchers may be eliminated by clarification of descriptions and definitions of study sites.