The impact of elevation and proximity to trails on plant biodiversity in mountain ecosystems surrounding Flagstaff, AZ, USA

Abstract

The objectives of this project were to compare biodiversity along an elevation gradient in the mountains surrounding Flagstaff, Arizona. In addition, identify the presence or absence of four specific non-native species being monitored using the Mountain Invasion Research Network (MIREN) protocol: common yarrow (Achillea millefolium), red clover (Trifolium pratense), white clover (Trifolium repens), narrowleaf plantain (Plantago lanceolata). The study used T-shaped transects at randomly selected sampling locations to collect data on richness and abundance of plant species up to 22 m from four hiking trails. Measured sample location was the middle point of the trailside or "near" sample unit. The "near" sample unit (2 m deep * 10 m parallel) was parallel with the trail. The other two sample units "middle" and "far" were perpendicular to the trail, starting 2 m from the measured sample location. Simpsons (1-D) and Shannon's Index were used to determine alpha biodiversity (diversity within a community (Magurran & McGill, 2011) along the elevation gradient. Jaccard Index and Morista-Horn Index used to compare dissimilarity of beta diversity (diversity between communities (Magurran & McGill, 2011)) between elevation zones and proximity to the trail. Dissimilarity is the amount of difference between communities. The study demonstrated species richness decreased as sample location elevation increased. Species richness also decreased as the distance from the trail increased. Simpson's and Shannon's biodiversity indices both showed a statistically significant difference in biodiversity values decreasing with an increase in elevation. Dissimilarity index values for both beta diversity indices indicated a statistically significant difference in dissimilarity based on proximity to the trail. The presence of common yarrow was only found at two sampling locations preventing further analysis. All trails had similar relative abundances but the dominant species along each trail was different. Elevation plays a determining role in the richness and diversity of species in mountain ecosystems surrounding Flagstaff, Arizona.