Various factors have been known to influence the percentage of mycorrhizal colonization in plants. However, it is unknown whether certain factors matter at different scales or if one or several factors have an overarching effect on controlling rates of mycorrhizal colonization in plants. In this thesis I assessed the percentage of mycorrhizal colonization in Schizhachyrium scoparium at 5 different sites that occur along a latitude gradient to determine which factors had an overarching effect and if there were site-specific differences in responses to nutrient addition. In the first chapter I present what factors affected the percentage of mycorrhizal colonization along a latitude gradient. I found that aridity was the only factor to contribute to changes in the percentage of mycorrhizal colonization. In my second chapter I used this information to account for differences between sites and assess responses in the percentage of mycorrhizal colonization among sites to see if there was a difference among sites. I found that the addition of nitrogen (N) decreased the percentage of mycorrhizal colonization in Schizachyrium scoparium across sites, but that the addition of phosphorus (P) had different effects among sites. Responses to the addition of P exhibited a U-shaped pattern in relation to ambient N:P ratio in soil at the sites. The results found in the first chapter of this thesis are novel and important to understanding plant-mycorrhizae relationships in plants while the results found in the second chapter agree with the current theory that exists to explain how resource stoichiometry affects the percentage of mycorrhizal colonization in plants.