Fixation of carbon dioxide by chemoautotrophic bacteria in grassland soil under dark conditions

Figures & data

Table 1. Description of plant characteristics of the study sites.

Sampling site	Species number	Coverage (%)	Aboveground biomass (g m^−2)	Shannon–Wiener Diversity Index	Dominant species
Grazing site	19	68.3 ± 7.6	156.7 ± 8.3	1.43 ± 0.27	Carex duriuscula; Cleistogenes squarrosa
Fenced site	22	91.7 ± 2.9	965.0 ± 54.1	1.16 ± 0.47	Leymus chinensis

Table 2. Primers used for amplification of cbbL gene.

Primer	Sequence (5′ to 3′)	Positions	Amplified region
cbbLRA	AARGAYGAYGARAAYATHAA	609–627	cbbL red-like gene
cbbLRB	ATNGTNCCNCCNCCRAAYTC	1206–1224
cbbLGA	GAYTTYACNAARGAYGAYGA	573–591	cbbL green-like gene
cbbLGB	TCYTCYTTDATYTCYTTCCA	1365–1383

Note: Y = C or T; S = G or C; R = A or G; H = A or C or T.

Table 3. Soil physicochemical characteristics of study sites in 0–5 cm layer.

Soil characteristic	GG	FG
Soil moisture (%)	6.94 ± 1.24	11.18 ± 1.13**
Soil pH (H2O)	6.97 ± 0.14	6.84 ± 0.07
EC (mS m^−1)	4.76 ± 0.87	9.02 ± 1.05**
Corg (g kg^−1)	18.81 ± 1.84	26.39 ± 2.60**
TN (g kg^−1)	2.00 ± 0.10	3.10 ± 0.41**
Soil C/N	11.18 ± 0.13	11.09 ± 0.26
Sand (%)	62.05 ± 3.59	56.87 ± 6.02
Silt (%)	14.43 ± 1.71	16.68 ± 2.11
Clay (%)	23.52 ± 2.03	26.45 ± 3.96
Exchangeable Ca^2+ (cmolc kg^−1)	11.03 ± 1.35	19.81 ± 1.83**
Exchangeable Mg^2+ (cmolc kg^−1)	2.70 ± 0.44	2.41 ± 0.07
Exchangeable K^+ (cmolc kg^−1)	0.77 ± 0.06	1.04 ± 0.14**
Exchangeable Na^+ (cmolc kg^−1)	0.21 ± 0.02	0.20 ± 0.03
Avail. P (mg kg^−1)	32.34 ± 7.38	39.21 ± 6.34
Cmic (mg kg^−1)	704.99 ± 127.20	1218.12 ± 118.22**
Nmic (mg kg^−1)	96.6 ± 21.53	159.4 ± 34.57**

Note: Average value and standard deviation; n = 5.

GG: grazing grassland site; FG: fenced grassland site; EC: electrical conductivity; C_org: organic carbon; TN: total nitrogen; soil C/N: soil carbon to nitrogen; Ca: calcium; Mg: Magnesuim; K: potassium; Na: sodium; Avail. P: available phosphorus; C_mic: microbial biomass carbon; N_mic: microbial biomass nitrogen.

*Significant difference between grazing and fenced grassland (P < .05).

**Significant difference between grazing and fenced grassland (P < .01).

Figure 1. The fixation rate of ¹⁴C-SOC and ¹⁴C-MBC in soils after incubation in darkness for 120 d.

Note: n = 3. GG and FG represent grazing grassland site and fenced grassland site, respectively.

Figure 2. Neighbor-joining phylogenetic tree of red-like cbbL genes in the grazing and fenced grassland soils.

Notes: Bootstrap values are known as percentage of 1000 bootstrap replicates. The bar indicates 10% estimated sequence divergence. Bootstrap values higher than 50% are shown at the branch points. G and F represent gene isolated from grazing and fenced site.