Presentation on theme: "Investigating the relationship between species richness and wilderness in the coastal temperate rainforest of Southeast Alaska. This poster represents."— Presentation transcript:
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. In spite of a wide range in latitude in the Pacific Northwest, a similarity in climate, habitat structure and composition is found throughout the region a. 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. 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 composition b, but what is the form of this pattern on Prince of Wales Island? by Crewenna Dymond, School of Geography, University of Leeds, UK Prince of Wales Island. From One Duck Trail looking towards the Karta River Wilderness
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 m 2 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 ( 12.5 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. 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 stricta b. Found throughout SE Alaska. 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 m b, 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. Change in species richness 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.
a Pojar, 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. b Dale, D.; Weaver, T. 1974, Trampling effects on vegetation of the trail corridors of North Rocky Mountain Forests. Journal of Applied Ecology. 11: 767-772. 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. 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 (<10 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. Collecting data on One Duck, an upland trail