Effects of soil temperature on fungal diversity and composition
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Cryptic species, such as soil fungi, represent a highly diverse and undiscovered group. These organisms are responsible for important ecological processes and ecosystem services that regulate the environment and provide economic value. Their composition and diversity directly impact these processes (Hunt et al., 2002, Wagg et al., 2013) Examining how different environmental factors drive their diversity and composition has been difficult in the past, but due to advances in molecular techniques we are now able to explore them further. Experimental studies suggest that pH, root exudates, concentrations nitrate and ammonium, C:N, soil moisture, and latitude all play a role in fungal composition; however, we lack an observational study isolating long- term temperature effects on soil fungal composition. Short term soil warming experiments have found significant changes in fungal composition and no changes in diversity. Due to the timescale of these experiments, ecological processes, such as immigration and emigration, do not have time to occur. This is necessary for stable shifts in community structure and adaptations to occur. Our aim is to determine if long term increases in soil temperature result in distinct communities and increased fungal diversity. We conducted a field study of four sites in Idaho (USA) surrounding hot springs to assess differences in fungal community composition between thermal (soils near the hot spring) and control (soils away from the hot spring) treatments at each site. We used next generation sequencing to determine fungal taxa abundance. We collected soil cores from the A horizon of plant associated soils at thermal (22.8-26.8⁰C) and control (16.8-17.9⁰C) treatments and quantified soil properties including: C:N, nitrate, ammonium, pH, and temperature. Based on a Permutational Multivariate Analysis of Variance we found a significant effect of treatment on fungal composition across sites (p<0.001). Fungal diversity, based on measures of species richness and Shannon-Weiner index, did not differ between treatments in three of the four sites. However, Weir creek hot spring, with the highest soil temperatures, had significantly higher diversity in thermal soils.