Investigating the relationship between species

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Investigating the relationship between species
richness and wilderness in the coastal temperate
rainforest of Southeast Alaska.
This poster represents part of a study of Prince
of Wales Island (PoW), Tongass National Forest,
Southeast Alaska. This work investigates how
species richness changes with distance from human
features, as an index of wilderness quality. Such
features include roads and forest tracks. This
has been facilitated by access to the 1998 USDA
Forest Service Southeast Alaska Inventory and
associated digital coverages such as roads for
the island. In addition, primary field data
collection enables a more detailed analysis of
the impact of recreational trails on species
richness at the micro scale and is the focus of
this poster.
Trampling impact Trails are one of the few
permitted impacts in designated wilderness
areas. Previous research has investigated how
trampling effects native flora but this has not
been done specifically for PoW. It has been
suggested that within short distances from the
trail there is little discernible impact on
species richness or compositionb, but what is the
form of this pattern on Prince of Wales Island?

Prince of Wales Island. From One Duck Trail
looking towards the Karta River Wilderness
In spite of a wide range in latitude in the
Pacific Northwest, a similarity in climate,
habitat structure and composition is found
throughout the regiona. In the global study,
climate was found to be a major determinant of
the distribution of species richness and
wilderness. Here, if there is any change in
species richness with wilderness quality we must
look towards explanations other than climate.
by Crewenna Dymond, School of Geography,
University of Leeds, UK

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Collecting field data from trails on Prince of
Wales Island Data collection took place in
June-July 2001 on PoW. In total six Forest
Service trails were surveyed and a total of 80
transects were taken. All tree, shrub and
herbaceous species were identified within the
transects. Four 1 m2 quadrats were taken at
distances of 0, 2, 5 and 10 m from the trail and
the abundance of herbaceous plants was recorded.
Shrubs, and by default, small trees (lt 5m in
height) were also identified within a 2 m wide
transect to 10 m from the trail. Distance of each
individual shrub from the trail was measured.
Trees (diameter gt12.5 cm) were identified within
a 10 m wide transect to 10 m from the trail and
again the distance of each individual tree from
the trail was measured.
Change in species richness
In the field a difference in composition was
observed between trails at low elevation, for
example on river corridors, and those that
climbed up into the hills. Analysis of the herb
quadrats revealed that at sites adjacent to the
trail (0 m), the mean species richness was higher
in the upland sites (2.56) than in valley ones
(1.877).
Slender bog orchid, Platanthera strictab. Found
throughout SE Alaska.
Figure 1 shows that the general trend is for
species richness to decline away from the trail
(all trails) and this pattern is also exhibited
by the valley trails.
In contrast, upland trails are more species rich
to begin with and the trail has less impact on
the species richness. If we accept that the
effect of trampling is not transmitted very far
into the forest, perhaps no more than 2 mb, we
can assume that at 10 m species richness is no
longer effected by the trail. At this distance,
unaffected by human impact, species richness is
lower than at the trail-side, in particular in
valley locations. The trail serves to unnaturally
increase the number of species that occupy the
site.
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Analysing composition with distance from trail
edge A Kruskal-Wallis test (non-parametric
one-way ANOVA) was used to determine difference
in the composition of herbaceous species with
distance from the trail. The test analyses the
medians of the populations at each of the quadrat
distances. If they are significantly different
they could be from different parent populations.
A significant difference (p 0.005) was found
between the sites. The z values indicate that
quadrats at 2, 5 and 10m are from the same
population whereas the population in 0 m quadrats
are statistically different. Furthermore, the
composition of 0 m quadrats in the valley
locations is different to those at 2 and 5 m and
that the 10 m quadrats were also distinct from
the others. As suggested by the analysis of
species richness, there was no significant
difference between the populations in the
quadrats of the upland trails.
Collecting data on One Duck, an upland trail
Summary Trails in valley locations have been
found to positively influence the species
richness of the surrounding vegetation. Upland
trail corridors do not seem to effect the species
richness of the surrounding vegetation to the
same extent. Further research using ordination
techniques is underway to further examine
compositional difference between the valley and
upland locations. On Prince of Wales Island
elevation has been found to contribute towards
the fluctuation in the response of species
richness to recreational trails. Minimal lateral
spread (lt10 m) in species richness from the trail
has been found to occur, but linear effects
should not be underestimated. Work is underway to
investigate the impact of clear cut forestry on
species richness to determine the relative
importance of trails as an impact in wilderness.
aPojar, J. MacKinnon, A. (Eds). 1994. Plants of
the Pacific Northwest Coast Washington, Oregon,
British Columbia and Alaska. BC Ministry of
Forests and Lone Pine Publishing, Vancouver.
bDale, D. Weaver, T. 1974, Trampling effects on
vegetation of the trail corridors of North Rocky
Mountain Forests. Journal of Applied Ecology. 11
767-772.