Vegetation Effects on Bacteria and Denitrifier Abundance in the Soils of Two Tidal Freshwater Wetlands in Virginia

Table 1

Soil physicochemical properties and microbial abundance data reported as means and standard errors.

Date	Site	Plant	Soil moisture (%)	Redox (mV)	pH	Organic matter (%)	C : N ratio	Bacterial abundance	Denitrifier abundance
November 2011	Rice	Reference soil	66 (8)^b	−15 (3)^b	6.6 (0.5)	16 (4)^B	15.7 (1.0)^A	230 (74)	9.0 (3.5)^C
		Juncus	46 (2)^c	276 (60)^a	6.9 (0.3)	6 (1)^C	15.5 (0.7)^A	378 (59)	22.1 (1.4)^B
		Peltandra	76 (2)^ab	−42 (12)^b	7.3 (0.5)	21 (1)^A	15.1 (1.3)^AB	232 (42)	16.3 (2.2)^B
		Typha	78 (2)^ab	2 (22)^b	7.8 (0.1)	25 (2)^A	13.8 (0.5)^B	417 (81)	42.0 (6.5)^A
		Overall	67 (4)	55 (36)	7.2 (0.2)^†	17 (2)^†	15.0 (0.4)	314 (37)	22.3 (3.6)
	James	Reference soil	80 (1)^ab	77 (17)	6.0 (0.1)	18 (2)^B	15.7 (0.8)^A	160 (40)	4.8 (0.6)^C
		Juncus	84 (1)^a	88 (34)	6.1 (0.1)	15 (2)^C	16.3 (0.4)^A	101 (27)	12.5 (5.8)^B
		Peltandra	81 (1)^ab	−3 (25)	5.8 (0.1)	26 (2)^A	14.9 (0.3)^AB	153 (38)	24.6 (7.4)^B
		Typha	78 (3)^b	−8 (35)	6.0 (0.1)	24 (2)^A	13.1 (0.6)^B	486 (162)	114.5 (47.4)^A
		Overall	81 (1)	39 (17)	6.0 (0.0)^‡	21 (1)^‡	15.0 (0.4)	189 (60)	39.1 (15.7)
June 2012	Rice	Reference soil	55 (3)^B	2 (40)^B	5.3 (0.2)^b	13 (1)^A	13.9 (0.7)^B	5 (1)^C	0.6 (0.2)^C
		Juncus	39 (6)^C	321 (45)^A	4.8 (0.1)^c	9 (2)^B	19.4 (2.4)^A	39 (13)^A	2.1 (0.8)^B
		Peltandra	56 (1)^AB	−29 (34)^B	5.7 (0.1)^ab	13 (2)^A	15.6 (0.6)^B	15 (2)^B	5.9 (0.9)^B
		Typha	62 (2)^A	16 (40)^B	5.8 (0.0)^a	14 (1)^A	13.8 (1.0)^B	13 (4)^B	6.3 (0.4)^A
		Overall	53 (3)^†	77 (37)	5.4 (0.1)	12 (1)	15.7 (0.8)^†	18 (4)^†	3.7 (0.6)^†
	James	Reference soil	62 (5)^B	−61 (31)^B	6.2 (0.1)^b	15 (2)^A	13.2 (0.5)^B	21 (7)^C	12.8 (4.3)^C
		Juncus	37 (3)^C	210 (21)^A	6.6 (0.1)^a	10 (2)^B	16.1 (1.0)^A	129 (25)^A	70.8 (22.0)^B
		Peltandra	70 (2)^AB	−37 (20)^B	6.6 (0.1)^a	24 (2)^A	12.9 (0.4)^B	63 (11)^B	63.8 (16.1)^B
		Typha	75 (2)^A	−37 (19)^B	6.7 (0.1)^a	24 (2)^A	12.4 (0.3)^B	55 (14)^B	65.6 (20.2)^A
		Overall	61 (4)^‡	11 (26)	6.5 (0.1)	18 (2)	13.6 (0.4)^‡	67 (12)^‡	53.2 (9.5)^‡

Each sampling date was analyzed using a two-factor ANOVA testing for site and plant effects. Whenever a significant site-by-plant interaction was obtained (), each site was reanalyzed separately, and Tukey’s HSD post hoc tests are reported using lowercase letters to distinguish plant effects at each location. In cases where the interaction effect was not significant, main effects are reported using uppercase letters (Tukey’s) for differences across plant types, and ^†/‡overall site effects. Units for abundance data are (×10⁶) gene copies gDW soil⁻¹.