The Effects of Soil Heating on AM Fungal Colonization in Two Desert Grasses.

Climate change is causing an increase in extreme climate events such as heat waves. Although understudied, these events may create legacy effects on future plant growth by affecting soil microbes. We selected two dominant grass species in a desert meadow, Bouteloua gracilis (C₄) and Festuca arizonica (C₃), and grew seeds for four months using potting soil and a small amount of rhizosphere soil collected from the same grass species. Before planting, we exposed rhizosphere soil to three heating disruption treatments: “heat-waved” at 45ºC, sterilized (microwaved), or left intact. After four months of growth in the greenhouse, the C₄ grass demonstrated a decrease in height, leaf number, chlorophyll and aboveground mass within heated and sterilized treatments. However, the C₃ grass performed the best when grown with sterilized soil. We hypothesize that C₃ and C₄ grasses exhibit differential interactions with their rhizosphere microbiome, with B. gracilis containing more microbial mutualists and F. arizonica containing more parasitic microbial communities. Currently, we are evaluating associated impacts to belowground biomass and AM fungal colonization within heated, intact, and sterilized soil treatments.