Impacts of trails on cliff-edge forest structure

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Abstract
Plant community structure and soil characteristics were quantitatively studied along forested cliff edges of the Niagara Escarpment in southern Ontario, Canada. The objective of the study was to try to differentiate between the effects of two gradients on vegetation structure: the environmental gradient between the cliff edge and dense forest, and an anthropogenic gradient, generated by the presence of major hiking trails parallel to the cliff edges. Species frequencies were determined along 69 transects distributed over eight sites with different amounts of past and present trampling disturbance. The data were analyzed using cluster and ordination analysis as well as analyses of variance. The results showed that soil characteristics were the major influence organizing the vegetation of cliff-edge forests and that soil properties and plant community structure were more strongly influenced by anthropogenic factors than by the environmental gradient between cliff edge and forest. Trampled plots had some properties in common with cliff-edge plots. Species richness was highest at intermediate trail-use levels; abandonment of heavily disturbed trails resulted in the restoration of species richness, but most new colonizing plants were disturbance-tolerant ruderals. Soil properties did not completely recover even after 10 years of trail abandonment. The results suggest that the current use of cliff edges along the Niagara Escarpment is nonsustainable, and reversing its effects on cliff-edge forest structure may take a considerable amount of time. Key words: Niagara Escarpment, plant community ecology, disturbance, trampling, cluster analysis, ordination.