N2O emission and its influencing factors in subtropical streams, China

Ecological Processes

Table 2 Sediment physicochemical variables of Jinshui River and Qi River

Sampling season	River	Sampling area	s-NO₃⁻(mg kg⁻¹)	s-NH₄⁺(mg kg⁻¹)	SOC (g kg^− 1)	SOC/NO₃⁻
High flow season	Jinshui River	Downstream	6.04 ± 2.12^a	5.74 ± 1.95	7.42 ± 1.87^b	1.30 ± 0.39
		Midstream	5.97 ± 4.47^b	4.83 ± 0.98	3.14 ± 0.48^c	2.09 ± 1.66
		Upstream	6.70 ± 2.34^a	5.99 ± 1.39	10.06 ± 0.80^a	1.80 ± 0.49
	Qi River	Downstream	6.79 ± 0.42^ab	6.17 ± 1.24^b	5.55 ± 2.39	1.35 ± 0.39
		Midstream	7.98 ± 0.74^a	8.61 ± 1.05^a	7.93 ± 6.14	0.65 ± 0.68
		Upstream	5.33 ± 1.74^b	5.52 ± 0.55^b	4.38 ± 0.72	1.03 ± 0.49
Normal flow season	Jinshui River	Downstream	1.34 ± 0.09	0.80 ± 0.47	3.47 ± 2.05	2.62 ± 1.61
		Midstream	0.82 ± 0.25	0.89 ± 0.55	5.74 ± 4.53	4.85 ± 4.71
		Upstream	1.22 ± 0.07	0.60 ± 0.10	9.48 ± 3.88	5.09 ± 2.83
	Qi River	Downstream	0.98 ± 0.22	1.19 ± 0.46	2.58 ± 3.43	7.01 ± 3.11
		Midstream	0.83 ± 0.32	1.13 ± 1.02	1.79 ± 1.13	5.32 ± 2.34
		Upstream	1.06 ± 0.73	1.26 ± 0.79	5.50 ± 3.53	7.50 ± 6.14
Low flow season	Jinshui River	Downstream	0.60 ± 0.16	3.43 ± 0.97	2.64 ± 1.11	4.59 ± 2.29
		Midstream	1.00 ± 0.07	2.19 ± 1.14	5.21 ± 3.46	3.32 ± 3.25
		Upstream	1.03 ± 0.37	2.44 ± 1.92	2.72 ± 0.40	5.36 ± 0.75
	Qi River	Downstream	1.81 ± 1.43	2.89 ± 0.67	2.87 ± 1.75	5.16 ± 1.21^a
		Midstream	0.94 ± 0.25	2.10 ± 0.72	1.47 ± 0.64	5.06 ± 0.27^a
		Upstream	0.58 ± 0.32	1.73 ± 0.59	3.26 ± 1.00	2.74 ± 4.39^b

Values are presented as mean ± SD (n = 3); different letters indicate significant differences among sampling areas by linear mixed modeling (P < 0.05). Abbreviations: the NO₃⁻ and NH₄⁺ concentration of sediment are denoted by s-NO₃⁻ and s-NH₄⁺. Sediment organic carbon concentration is denoted by SOC. The ratio of sediment organic carbon to NO₃⁻ in sediment is denoted by SOC/NO₃⁻