Searching the soil: characterizing the effects of disturbance on soil microbial communities and plant productivity

Abstract

The effects of global climate change are accelerated and more pronounced in northern regions, and Alaska is at the forefront of that change. Permafrost, which underlies much of the Alaskan landscape, is rapidly thawing and degrading leading to shifts in hydrology, soil chemistry, and nutrient availability. As permafrost thaws, soil microbial communities have the potential to be influenced taxonomically and functionally. However, it is unclear how active layer microbial communities, which play a role in plant-microbe interactions, are affected by increasing soil disturbance, and how soil microbiomes can influence above ground plant communities. In this study, I aimed to understand how soil microbial communities from Interior Alaska are affected by increasing disturbance, and how they in turn drive the productivity of several plants found in boreal regions. Here I used a growth experiment and found that plant productivity was affected by the disturbance level of the microbial inoculant. Plants grown in soils inoculated with microbes associated with disturbed soils demonstrated significantly decreased productivity compared to plants inoculated with microbes from undisturbed soils. Through metagenomic sequencing, I observed broad scale shifts in community membership across the gradient of soil disturbance. I then continued to characterize the microbial communities used as inoculants in the greenhouse growth experiment through 16S rRNA amplicon sequencing. Microbial communities from disturbed soils were significantly more diverse than those from undisturbed soils, and the beta diversity of communities varied significantly based on the disturbance level. We found that within disturbance level community variation can be used to predict plant growth of bog blueberry, low-bush cranberry, and Labrador tea once the disturbance passes a threshold. These results suggest that as active layer microbial communities are affected by climate-driven soil disturbance, above ground plant communities may demonstrate decreased productivity, and consequently, decreased ecosystem health as the Arctic continues to warm.