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Title: Plant nitrogen uptake drives rhizosphere bacterial community assembly during plant growth

Author
item BELL, COLIN - Colorado State University
item ASAO, SHINICHI - Colorado State University
item Calderon, Francisco
item WOLK, BRETT - Colorado State University
item WALLENSTEIN, MATTHEW - Colorado State University

Submitted to: Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2015
Publication Date: 3/23/2015
Publication URL: http://handle.nal.usda.gov/10113/62019
Citation: Bell, C., Asao, S., Calderon, F.J., Wolk, B., Wallenstein, M. 2015. Plant nitrogen uptake drives rhizosphere bacterial community assembly during plant growth. Soil Biology and Biochemistry. Available: http://dx.doi.org/10.1016/j.soilbio.2015.03.006.

Interpretive Summary: In this experiment we show how plants can affect the microbial composition of soils via their effects on soil nitrogen. Plants like cheatgrass, which are notorious for their ability to out-compete other grasses in the High Plains of North America, have developed strategies to ensure their survival. In this manuscript, we show that cheatgrass can promote the rapid conversion of soil nitrogen into plant-available nitrogen at the same time that it changes the soil microbial composition to one that can survive under low soil nitrogen conditions. We propose that with this strategy, cheatgrass can enhance its competitiveness and establishment into new areas, as well as modifying soil biology to its own favor.

Technical Abstract: When plant species establish in novel environments, they often modify microbial communities and soil properties in ways that enhance their own success. Upon invasion, the C3 annual grass Bromus tectorum appears to support soil microbial communities that have higher soil nitrogen (N) mineralization rates, which facilitates higher plant N uptake compared to native grass species. We hypothesized that plant N uptake within the rhizosphere can influence microbial community assembly. We found that plant N uptake rates inversely corresponded to microbial biomass N and strongly correlated with shifts in microbial community structure within the plant rhizosphere during periods of plant growth. Furthermore, microbial community diversity and richness (i.e. Shannon’s Diversity and Chao 1) significantly dropped within plant rhizospheres early in the growing season when plant N uptake was high. This suggests that during periods of high plant N uptake, rapid depletion of soil N can lead to a rapid die-off within the rhizosphere microbial community, whereby only those microbes able to tolerate low N availability survive. Our results suggest that plant nutrient uptake is a key mechanism through which plants engineer microbial community structure and function.