per hour (pre-fencing) to less than one per hour, while in the open sector the
trampling intensity remained relatively constant during the study period.
In May 2007, immediately after the fencing systems had been put in place,
random vegetation sampling was performed in the three dune sectors using
georeferenced points located with a GPS (10 points in each sector, for a total of 30
points). At each randomly assigned point, all vascular plant species were sampled
in a 2-m 9 2-m (4-m
2 ) plot. In each of these plots we recorded plant species found
along with the percentage cover of each species using a 10 %-interval rank scale.
In 2007, just after the erection of the fences, the three sectors showed no significant difference in cover (linear mixed-effects model of vegetation cover in relation to the sector of each plot and distance from the sea as a correction factor).
Sampling was repeated during the same period of the year and at the same points
from 2007 to 2010.
12.3.2 Effects of Limitations to Human Trampling
on Vegetation Cover and Richness
As of 2010, only 4 years after the enclosures were set up, the two fenced sectors
showed a considerable increase in vegetation cover, which in both cases had
become significantly higher than that of the open sector. Moreover, plant cover in
both the north and south fence increased linearly during the study period
(Fig. 12.3). For the most part this observed trend was due to an increase in cover of
pre-existing species (species sampled in 2007 at the beginning of the study), and
not to the colonization by new, incoming species.
Species richness was also strongly influenced by enclosure, but in a slightly
different way. As was the case for plant cover, by 2010 species richness in both of
the fenced areas had increased and had become significantly greater than that of the
open sector. However, whereas cover increased linearly through time, the response
in species richness showed a lag period and the increase in the number of species
recorded per plot only occurred after the second year of enclosure (Fig. 12.4). In
terms of the composition of the new species pool, results were particularly
encouraging. Indeed, for the most part the increase in richness was attributable to
colonization by species characteristic of coastal dune habitats. Among these were
annuals such as Lagurus ovatus, Silene canescens, and Vulpia fasciculata, but also
important sand dune geophytes like Pancratium maritimum. These species are
widespread pioneers that produce a large number of seeds dispersed along the dunes
by wind and waves (Watkinson 1978; Balestri and Cinelli 2004).
Another interesting result that emerged from the present study was the important
role played by the environmental gradient that characterizes dune ecosystems.
Factors of stress and disturbance, such as sea or wind erosion, salt spray, and sand
burial, are typical of dune ecosystems and play a major role in shaping plant communities (Wilson and Sykes 1999; Forey et al. 2008; Maun 2009). The degree of
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A. T. R. Acosta et al.
trampling intensity remained relatively constant during the study period.
In May 2007, immediately after the fencing systems had been put in place,
random vegetation sampling was performed in the three dune sectors using
georeferenced points located with a GPS (10 points in each sector, for a total of 30
points). At each randomly assigned point, all vascular plant species were sampled
in a 2-m 9 2-m (4-m
2 ) plot. In each of these plots we recorded plant species found
along with the percentage cover of each species using a 10 %-interval rank scale.
In 2007, just after the erection of the fences, the three sectors showed no significant difference in cover (linear mixed-effects model of vegetation cover in relation to the sector of each plot and distance from the sea as a correction factor).
Sampling was repeated during the same period of the year and at the same points
from 2007 to 2010.
12.3.2 Effects of Limitations to Human Trampling
on Vegetation Cover and Richness
As of 2010, only 4 years after the enclosures were set up, the two fenced sectors
showed a considerable increase in vegetation cover, which in both cases had
become significantly higher than that of the open sector. Moreover, plant cover in
both the north and south fence increased linearly during the study period
(Fig. 12.3). For the most part this observed trend was due to an increase in cover of
pre-existing species (species sampled in 2007 at the beginning of the study), and
not to the colonization by new, incoming species.
Species richness was also strongly influenced by enclosure, but in a slightly
different way. As was the case for plant cover, by 2010 species richness in both of
the fenced areas had increased and had become significantly greater than that of the
open sector. However, whereas cover increased linearly through time, the response
in species richness showed a lag period and the increase in the number of species
recorded per plot only occurred after the second year of enclosure (Fig. 12.4). In
terms of the composition of the new species pool, results were particularly
encouraging. Indeed, for the most part the increase in richness was attributable to
colonization by species characteristic of coastal dune habitats. Among these were
annuals such as Lagurus ovatus, Silene canescens, and Vulpia fasciculata, but also
important sand dune geophytes like Pancratium maritimum. These species are
widespread pioneers that produce a large number of seeds dispersed along the dunes
by wind and waves (Watkinson 1978; Balestri and Cinelli 2004).
Another interesting result that emerged from the present study was the important
role played by the environmental gradient that characterizes dune ecosystems.
Factors of stress and disturbance, such as sea or wind erosion, salt spray, and sand
burial, are typical of dune ecosystems and play a major role in shaping plant communities (Wilson and Sykes 1999; Forey et al. 2008; Maun 2009). The degree of
192
A. T. R. Acosta et al.