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

微生物群落是土壤有机质分解和养分循环的重要调节因子。在亚利桑那州和新墨西哥州等干旱地区，大约一半的年总降水量发生在夏季季风季节，此时植物生长迅速，养分需求高。本研究将探讨季风降雨和植物生长如何影响这些干旱地区的土壤微生物群落。将进行三个独立的实验，以评估土壤微生物群如何受到以下因素的影响：1)加水时间；2)湿度程度；3)植物生长。随着浇水，细菌群落组成预计会发生瞬时变化，而真菌群落的反应预计会延迟。在不保湿的地块上，细菌和真菌群落结构的变化预计不太明显。最后，植物去除有望防止许多真菌种群和一些细菌菌株的建立。干旱地区的生态系统正在发生变化，草原被沙漠灌木所取代。了解土壤微生物群落对季节性降雨的反应对于理解沙漠生态系统中的有机质分解和养分循环至关重要，而这反过来又对理解植被动态至关重要。与当地一所为美国原住民服务的K-8学校合作，将使研究人员能够将他们的研究带入课堂，课程以三姐妹种植计划为中心——一种传统的美国原住民玉米、豆类和南瓜的伴生种植。

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.