The effect on coastal vegetation of trampling on a parabolic dune

This paper examines the effect of trampling activity and intensity on the vegetation growing up the central axis of a tropical coastal parabolic dune at La Mancha, Veracruz State, Mexico. A trampling path was established across the dune with slopes varying from 1° to 34°, and the vegetation cover and richness was sampled after 0, 10, 30, 50, 70 and 100 tramplings. There was a significant decline in relative cover over time as the trampling intensity increased, and rare species disappeared after only 10 tramplings. As the slope increased the rate of decline of relative cover of the dominant species also increased. Within the steeper slope segments of the path (21-25, >25, crest, and relic slipface down-slope segments) between 40% and 80% of the number of species disappear from the survey transect by 100 cumulative tramplings, whereas, only 13-30% of the number of species disappeared from the survey transect within the low/moderate slope segments by 100 cumulative tramplings. Within the 21-25° slope segment, a staircase morphology was gradually created, while at higher slopes, shearing occurred and linear debris slopes were formed. There was a greater decrease in richness values on steep slopes compared to low/moderate slope angles, independent of trampling intensity. Apart from the 21-25° slope, the creation of bare surface area does not appear to be related to slope angle as trampling increases.