| Sumario: | Mycorrhizas are mutualistic relationships between fungi and vascular plants. Mycorrhizal associations are important for plants because they provide minerals, especially phosphorous, and water, while the plant provides carbohydrates for the fungi. Trail edges affect plant community diversity by altering water runoff and soil moisture or encouraging growth of invasive species. Because trail edges impact plant communities, I hypothesize mycorrhizal colonization frequency may decrease as distance to a trail edge decreases. To test this hypothesis, Gutierrezia sarothrae [Asteraceae], a woody shrub native to the western United States, was sampled from two similar sites and at three distances from hiking trails and mycorrhizal colonization frequency was determined. Plant samples were collected 1 m, 10 m,, and 20 m from the edge of the hiking trail. Roots were cleared and stained with trypan blue. A statistical significance overall was determined via chi-square analysis (p<0.0001; X=47.41; df=2). It is important to note, after the study was completed, old aerial photographs were discovered showing the existence 10 years earlier of a hiking trail intersecting site B at the 20meter sample location. This trail had since been abandoned at the time of the study. Based on the elucidation of an old trail, the hypothesis was subsequently supported by illustrating the long-term effect on the microscopic community. The results showed differential mycorrhizal colonization frequency, suggesting a negative response near trail edges. Understanding how mycorrhizas respond to disturbance can help land managers understand the effects of recreational land use on plant communities.
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