Influence of increasing temperature and nitrogen input on greenhouse gas emissions from a desert steppe soil in Inner Mongolia

Figures & data

Figure 1. Monthly precipitation (bars) and mean monthly air temperature (line) from January 2006 to December 2007 in a desert steppe. Data was measured at a micro-meteorological station located adjacent to the experimental site.

Table 1. Average desert steppe soil temperature (in °C) in heating (H₁) and no heating (H₀) treatment over the study period in different soil depth

Treatment	Season	Surface (0 cm)	7.5 cm	15 cm	30 cm	50 cm
H1	Spring	16.7 ± 0.1†	3.7 ± 0.5	4.5 ± 0.4	4.6 ± 0.5	2.7 ± 0.4
	Summer	27.2 ± 0.1	22.7 ± 0.3	21.7 ± 0.1	21.3 ± 0.1	19.8 ± 0.1
	Autumn	19.8 ± 0.1	16.8 ± 0.8	16.2 ± 0.5	16.6 ± 0.3	16.7 ± 0.3
	Winter	−6.3 ± 0.1	−4.4 ± 0.3	−3.9 ± 0.3	−5.4 ± 0.4	−7.7 ± 0.3
H0	Spring	15.1 ± 0.1	2.8 ± 0.2	3.3 ± 0.8	3.4 ± 0.9	1.6 ± 0.6
	Summer	26.2 ± 0.1	21.9 ± 0.2	20.9 ± 0.1	20.6 ± 0.1	19.2 ± 0.1
	Autumn	18.2 ± 0.1	15.6 ± 0.3	15.1 ± 0.4	15.6 ± 0.2	16.0 ± 0.3
	Winter	−8.0 ± 0.1	−4.6 ± 1.0	−3.8 ± 0.7	−5.7 ± 0.8	−8.3 ± 0.9
†Average and standard error, obtained using bi-weekly measurements over each season.

Figure 2. Soil volumetric moisture content in heated (H₁) and unheated (H₀) treatments recorded by sensors that were installed at three depths (10, 20 and 30 cm) during the entire study period.

Table 2. Average carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) concentration (in µL L⁻¹) in soil profile (0, 7.5, 15, 30 and 50 cm) in different seasons over the study period in a desert steppe†

	CO2				CH4				N2O
	Spring	Summer	Autumn	Winter	Spring	Summer	Autumn	Winter	Spring	Summer	Autumn	Winter
H^1	586B	861A	527B	392B	1.03C	1.32BC	1.41B	1.98A	0.337A	0.323A	0.332A	0.331A
H^0	566B	911A	524B	377B	0.95C	1.19BC	1.39B	1.93A	0.330B	0.321A	0.332A	0.331A
Surface
(0 cm)	404dA	448eA	409cA	410aA	2.04aA	2.00aA	2.00aA	2.00abA	0.325bA	0.319bA	0.330aA	0.327aA
7.5 cm	531cB	791dA	510abB	403aB	1.14bB	1.28bB	1.43bB	2.06aA	0.335aA	0.322abA	0.332aA	0.332aA
15 cm	572cB	898cA	498bB	386aB	0.66cC	1.11cB	1.27cB	2.04abA	0.335aA	0.323aA	0.332aA	0.332aA
30 cm	660abB	1117bA	567bB	360aB	0.54dC	0.95dB	1.15dB	1.92bA	0.338aA	0.324aA	0.336aA	0.332aA
50 cm	713aB	1174aA	641aB	364aC	0.57cdC	0.91dB	1.14dB	1.77cA	0.334aA	0.323aA	0.331aA	0.332aA
†Data in a column followed by different lowercase letters shown significantly different among different depth at P < 0.1. Different uppercase letters in row significantly different among different season at P < 0.05. H1, heating treatment; H0, no heating treatment.

Figure 3. The surface flux of greenhouse gases (a) carbon dioxide (CO₂), (b) methane (CH₄) and (c) nitrous oxide (N₂O) from a desert steppe soil in relation to heating and nitrogen fertilizer treatments (H₁F₀, heating no fertilizer application; H₁F₁, heating fertilizer application; H₀F₀, no heating no fertilizer application; H₀F₁, no heating fertilizer application).

Table 3. The effects of heating, soil nitrogen level, season and their interactions on seasonal greenhouse gas flux rates over the whole study period from a desert steppe soil†

	CO2 (mg cm^−2h^−1)				CH4 (µg C m^−2h^−1)				N2O (µg N m^−2h^−1)
Season	H1	H0	F0	F1	H1	H0	F0	F1	H1	H0	F0	F1
Spring	6.4bA	5.9bA	5.7bA	6.6bA	−37.2abB	−18.2aA	−24.3aA	−31.0abA	4.3aA	3.6aA	3.5aA	4.4aA
Summer	28.4aA	30.8aA	33.6aA	25.6aB	−40.2bA	−53.0bB	−52.6bA	−40.6bA	3.5abA	3.4aA	3.4aA	3.6abA
Autumn	13.8bA	12.6bA	12.1bA	14.2bA	−31.1abA	−42.7bA	−34.0abA	−39.8bA	3.2abA	3.1abA	2.8abA	3.5abA
Winter	4.2bA	8.6bA	7.7bA	4.9bA	−15.3aA	−15.5aA	−16.4aA	−14.5aA	3.0bA	2.1bA	1.9bA	3.2bA
†Data in a column followed by different lowercase letters significantly different between different seasons at P < 0.05. Uppercase letters significantly different between heating and no heating, fertilizer application and no fertilizer application at P < 0.05. H1, heating treatment; H0, no heating treatment; F0, no fertilizer application; F1, fertilizer 100 kg N ha^−1 application.

Table 4. Annual rate of carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) emissions over the experimental period from the desert steppe soil†

	CO2 (kg C ha^−1year^−1)		CH4 (kg C ha^−1year^−1)		N2O (kg N ha^−1 year^−1)
Parameter	F0	F1	F0	F1	F0	F1
H0	1580 ± 217	1163 ± 48	−3.22 ± 0.54	−2.93 ± 0.39	0.220 ± 0.059	0.315 ± 0.055
H1	1147 ± 125	1245 ± 186	−2.57 ± 0.43	−2.70 ± 0.34	0.296 ± 0.057	0.321 ± 0.081
†H1, heating; H0, no heating; F0, no fertilizer application; F1, 100 kg N ha^−1year^−1 fertilizer application.

Table 5. Relationships between mean daily greenhouse gas (GHG) flux rates and mean daily soil temperature (7.5 cm), moisture (10 cm) over the two year study period in the desert steppe

GHG flux†	Parameters	Intercept	Slope	r  ^2	P > F
CO2-C (mg C m^−2h^−1)
	Soil temperature (°C)	9.33	0.40	0.16	<0.001
	Soil moisture (m^3m^−3)	9.64	132.30	0.20	<0.001
CH4-C (µg C m^−2h^−1)
	Soil temperature (°C)	−26.71	−0.69	0.06	0.042
	Soil moisture (m^3m^−3)	−27.79	−152.28	0.09	0.006
N2O-N (µg N m^−2h^−1)
	Soil temperature (°C)	3.04	0.03	0.01	0.311
	Soil moisture (m^3m^−3)	2.89	5.03	0.02	0.266
†There are 104 daily GHG flux data points used in the linear regression model.