Dissertation Research: Impact of monsoon rains on soil microbial communities in an arid grassland

Northern Arizona University, Flagstaff AZ

Investigators

Abstract

Microbial communities are important regulators of organic matter decomposition and nutrient cycling in soils. In arid regions such as Arizona and New Mexico about half of the annual total precipitation occurs during the summer monsoon season when plant growth is rapid and nutrient requirements are high. This study will investigate how monsoon rains and plant growth impact the soil microbial community in these arid regions. Three separate experiments will be conducted to assess how soil microbial biota is influenced by 1) timing of the water addition, 2) degree of moisture, and 3) plant growth. Instantaneous changes in bacterial community composition are expected with watering, while a delayed response is predicted for the fungal community. In plots where moisture is withheld, changes in the structure of both bacterial and fungal communities are predicted to be less pronounced. Finally, plant removal is expected to prevent establishment of many fungal populations and some bacterial strains. Arid land ecosystems are undergoing change with grasslands being replaced by desert shrubs. Understanding how the soil microbial community responds to seasonal rains is critical to understanding organic matter decomposition and nutrient cycling in desert ecosystems, which in turn, is important for understanding vegetation dynamics. A partnership with a local Native American-serving K-8 school will allow the researchers to bring their research into the classroom, with lessons centering on the three sisters planting scheme -- a traditional Native American companion planting of corn, beans, and squash.