Vertical Distribution of Wetland Plant Roots and their Associated Bacteria in Groundwater-Fed Wetlands

As part of the effort to understand the community structure of bacteria and archaea in groundwater fed wetlands, the vertical distribution of plant root density and species presence was studied in correlation with the change in associated bacterial and archaeal communities. Three sampling sites at a local groundwater fed wetland were selected based on surface plant community structure: Site 1 was dominated by Carex stricta, site 2 was dominated by Eleocharis erythropoda, and site 3 was dominated by a 50/50 mix of C. stricta and E. erythropoda. Core samples at 4 depths down to 1.2 m were taken to collect data on soil moisture, root density, organic matter content, plant species presence, bacteria taxa presence, and quantification of bacteria taxa. DNA sequences were used to identify plants, bacteria, and archaea. Between 13,000 – 25,000 bacterial and archaeal species are estimated to be present at each depth, with the greatest diversity found in the upper layers. Species estimates were positively correlated with soil moisture, organic content, and root mass. In total, 242 microbial classes were found with a Simpson\u27s dominance index \u3c 0.09, Shannon\u27s diversity index \u3e 3.13, and Shannon\u27s equitability \u3e 0.60, indicating a high diversity and somewhat even abundance. Compared to other wetlands, diversity indices are highest in wetlands with hydrology similar to fens (sub-surface vertically-flowing water). All soil parameters significantly (p \u3c 0.05) influenced overall microbial community composition; most significantly the presence of dechlorinators, ammonia oxidizers, and methane oxidizers. Sub-surface samples revealed a greater species richness of plants than was expected from surface sampling; 22 species were found through surface survey and 25 species were found through DNA analysis. E. erythropoda (p \u3c 0.05) significantly influenced overall changes in microbial communities. Of the 25 plants, 12 plants were correlated with specific functional groups, with at least one plant strongly (p \u3c 0.10) correlated with each functional group