Greater change in arbuscular mycorrhizal fungal richness as a response to short-term rainfall exclusion across the North American Monsoon season

Arid ecosystems around the world are projected to experience reduced and moreinfrequent precipitation events. The effects of reduced rainfall are well understood forplants and aboveground interactions, however the effect of rainfall on belowgroundmicrobial interactions remains understudied. Here, we illustrate the strength anddirection of change short term manipulative rainfall exclusion treatments have on thecomposition and relative abundance of Arbuscular Mycorrhizal (AM) fungalcommunities throughout the monsoon season in the Sonoran Desert. Additionally, weuse these rainfall exclusion treatments to further understand the impact of soil moistureon labile forms of nitrogen and phosphorous in a natural environment. Rainfallexclusion treatments were installed to remove 0% (control), 60% (moderate exclusion),and 80% (high exclusion) of rainfall over a single wet season. AM fungal communitycomposition varied among rainfall treatments and across the monsoon season, wherechange was dependent on initial conditions within treatments. Phosphorous contentwas also a strong predictor of AM fungal composition and relative abundance. By theend of the season, the difference in AM fungal richness was influenced by rainfallexclusion, with the greatest positive change in richness in the moderate removaltreatments. Lastly, AM fungal community turnover was predicted by rainfall exclusiontreatments where rainfall contributed to greater turnover in the control treatment incomparison to other treatments. This study further illustrates the complex associationbetween soil abiotic factors, how they are influenced by environmental stress, and howin turn cause shifts in AM fungal communities.