Arbuscular mycorrhizal fungal communities vary as a response to short-term rainfall exclusion in the Sonoran Desert

Background/Question/Methods

Dry, arid ecosystems around the world are projected to experience shifts towards reduced and more infrequent precipitation events. The effects of reduced rainfall are well understood for plants and aboveground interactions, however the effect of rainfall on belowground microbial interactions remains understudied. Many recent studies have illustrated the importance soil moisture plays on arbuscular mycorrhizal (AM) fungal colonization and persistence in greenhouse studies. Here, we illustrate the effect that manipulative rainfall exclusion shelters and sampling date have on the composition and relative abundance of AM fungal communities throughout the Sonoran Desert monsoon season. Additionally, we used these rainfall exclusion treatments to further understand the impact soil moisture has on labile forms of nitrogen and phosphorous in a natural environment. Rainfall exclusion treatments were installed to remove 0% (control), 60% (moderate removal), and 80% (high removal) of rainfall over a single wet season.

Results/Conclusions

AM fungal community composition and relative abundance varied among rainfall treatments across the monsoon season. Phosphorous content was also shown as a strong predictor for AM fungal composition and relative abundance. By the end of the season, the difference in AM fungal richness was influenced by rainfall exclusion, with moderate removal showing the greatest positive change in richness. Lastly, AM fungal pairwise community turnover was predicted by rainfall exclusion treatments where rainfall contributed to greater turnover in the control treatment in comparison to other treatments. This study further illustrates the complex association between soil edaphic factors, how they are influenced by environmental stress at a regional scale, and how in turn cause shifts in AM fungal communities.