Figure 2: Plant-effect ratio for (a) bacteria and (b) denitrifier abundance associated with the rhizosphere of three plant species (Juncus effuses, Peltandra virginica, and Typha latifolia). Values are plotted as means and standard errors. A plant-effect ratio of “1” (dashed horizontal line) indicates that abundance in the rhizosphere samples was the same as abundance in the reference (unvegetated) soil. Bars with (for 0.01 ) and (for ) above them indicate the period when rhizosphere samples had significantly greater abundance than reference soils as determined via t-test. For bacteria (a), two-factor ANOVA of the effect ratios found no significant plant or site effects for either sampling date. For denitrifiers (b), main effects of site and plant type were significant for both sampling dates. Results of Tukey’s HSD post hoc tests comparing plant types are presented using letters beneath each bar (lowercase for November and uppercase for June).