Rhizospheric bacterial communities respond to changes in rainfall exclusion throughout the North American Monsoon season
As dry climates begin to experience greater extremes in seasonal rainfall and warming, interactions between plants and belowground microbial communities may experience change. Rhizosphere microhabitats are temporally dynamic and covary with abiotic conditions, such as soil moisture. While there is extensive knowledge on how abiotic conditions affect rhizosphere microbial richness, more knowledge is needed to understand how sustained changes in abiotic conditions over seasonal time scales effect community composition. Here, we used Lupinus neomexicanus and the North American Monsoon season to test the following question: to what degree does rainfall exclusion treatments affect rhizosphere bacterial community composition across the monsoon season? Monsoon rainfall exclusion treatments were added to remove 60% (moderate exclusion), and 80% (high exclusion) of rainfall on the rhizosphere microhabitat. Additionally, soil abiotic factors (i.e., nitrogen and phosphorous content), were also measured at the beginning and at the end of the monsoon season. Our results presented in this study illustrate that bacterial communities varied in community structure and phylogenetic membership among rainfall exclusion treatments. After rainfall exclusion, bacterial community structure varied by phosphorous. Bacterial alpha diversity by the end of the monsoon season was predicted by rainfall exclusion treatment as well as ammonium. In addition, a shift in the main abiotic predictor of bacterial alpha diversity was observed from nitrate to ammonium. suggesting that bacterial communities can experience compositional shifts due to soil abiotic factors in addition to rainfall exclusion. We illustrate that rhizosphere bacterial communities can experience compositional shifts due to soil abiotic factors and seasonal rainfall events despite plant hosts providing an ecological buffer to external environmental stress.