Characteristics and environmental factors controlling methane emission from a Sphagnum bog with different plant cover types in a subalpine area, southwest of Hubei, China

doi:10.17521/cjpe.2020.0292

Abstract

Abstract:

Aims Wetlands are important sources of atmospheric methane (CH₄), but there are few reports on the CH₄ emissions of subtropical and subalpine wetlands. In particular, the accurate estimation of CH₄ emissions from plots with different types of plant cover and the controlling environmental factors are not clear. The objective of this study is to study characteristics and influencing factors of CH₄ emission fluxes from a Sphagnum bog with different plant cover types in a subalpine area, southwest of Hubei Province.
Methods A Sphagnum bog in the subalpine area in southwest of Hubei Province was selected, and CH₄emission fluxes were measured in the Sphagnum bog with three types of plant cover using closed static chamber and gas chromatography method from November 2018 to October 2019. Simultaneously, air temperature, soil temperature of 5 cm depth, and groundwater level were recorded.
Important findings (1) Under sunlight, the CH₄-C fluxes from the bare land plot (B), the Sphagnum paluster plot (S), and the Polytrichum commune plot (P) varied throughout the year within the following ranges: 0.012- 1.372, 0.022-1.474 and 0.027-3.385 mg·m^-2·h^-1, respectively; under shading treatment, the variation range of CH₄-C flux throughout the year from B, S and P plots were 0.012-1.372, 0.009-1.839 and 0.017-2.484 mg·m^-2·h^-1, respectively, indicating CH₄emission sources for all types. At the same time, for all plant cover types, CH₄ emissions under sunlight conditions were slightly higher than those under dark conditions, but the difference was not significant. (2) For all plant cover types, CH₄ emissions showed obvious seasonal variations, with the order of summer > autumn > spring > winter; and summer emissions were significantly greater than emissions in other seasons, accounting for about 57% to 84% of the annual cumulative flux. This study found that the flux of CH₄ emission was highly related to air temperature and soil temperature of 5 cm depth showing exponential relationships, which indicated that temperature is the main environment factor affecting the temporal variations of CH₄ emission from the Sphagnum bog. (3) Plant cover types significantly affected CH₄ emissions from theSphagnum bog. The annual average and cumulative CH₄ emissions from the three cover types were in the order of: P > S > B. P plot showed significantly higher emission than B plot. This study found a significant correlation between vegetation types and CH₄ emissions, indicating that plant cover type is the main influencing factor of the spatial variations of CH₄ emissions from the Sphagnum bog. (4) CH₄ emissions were not significantly related to the groundwater levels. This study further enriched the mechanisms of CH₄ emission in the Sphagnum bog and provided basic data for regional carbon cycling.

Key words: subtropical, vegetation type, marshland, methane emission

MOU Li, WU Lin, LIU Xue-Fei, LI Xiao-Ling, WANG Han, WU Hao, YU Yu-Rong, DU Sheng-Lan. Characteristics and environmental factors controlling methane emission from a Sphagnum bog with different plant cover types in a subalpine area, southwest of Hubei, China[J]. Chin J Plant Ecol, 2021, 45(2): 131-143.

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https://www.plant-ecology.com/EN/Y2021/V45/I2/131

Figures/Tables 10

Fig. 1 Distribution patterns of three cover types in the studied Sphagnum bog.

Fig. 2 Diurnal changes of methane (CH4) emission fluxes in the Sphagnum bog (mean + SE). ▲, bare land plot; ■, Sphagnum paluster plot; ●, Polytrichum commune plot. The lines represent soil temperature at 5 cm depth, the lines with points represent CH4 emission fluxes, the bars represent air temperature. * represents a significant difference among the three cover types at the same time (p < 0.05), ** represents a significant difference among the three cover types at the same time (p < 0.01).

Table 1 Results of repeated measures ANOVAs on the effects of vegetation type, season, and their interactions on methane emission fluxes of the Sphagnum bog

方差来源 Source of variance	自由度 df	光照 Light			黑暗 Dark
方差来源 Source of variance	自由度 df	均方根 Mean square	F	p	均方根 Mean square	F	p
季节 Season	3	9.33	39.99	<0.01	4.55	39.67	<0.01
植被类型 Vegetation type	2	1.12	8.97	0.022	0.36	60.53	0.003 8
季节×植被类型 Season × Vegetation type	6	0.42	1.80	0.17	0.11	0.92	0.523

Fig. 3 Seasonal changes in methane emission fluxes in the Sphagnum bog (mean ± SE). B, bare land plot; P, Polytrichum commune plot; S, Sphagnum paluster plot. Different uppercase letters indicate significant difference among the same cover type in different seasons (p < 0.01); different lowercase letters indicate significant difference among the annual methane emissions of three cover types (p < 0.05). * represents a significant difference among the three cover types at the same season (p < 0.05); ** represents a significant difference among the three cover types at the same season (p < 0.01).

Fig. 4 Relationship between methane emission fluxes and air temperature in the Sphagnum bog. B, bare land plot; P, Polytrichum commune plot; S, Sphagnum paluster plot.

Fig. 5 Relationship between methane emission fluxes and soil temperature of 5 cm depth in the Sphagnum bog. B, bare land plot; P, Polytrichum commune plot; S, Sphagnum paluster plot.

Fig. 6 Relationship between methane emission fluxes and water table in the Sphagnum bog. B, bare land plot; P, Polytrichum commune plot; S, Sphagnum paluster plot.

Fig. 7 Schematic diagram of methane emission flux of the Sphagnum bog in different regions. This comprehensive diagram is based on methane emission flux measured by Nykanen et al.(1998), Beetz et al.(2013), Hanson et al.(2016) and this study.

Table 2 CH4-C emission fluxes from the Sphagnum bog in different regions

研究区 Study area	沼泽类型 Wetland type	研究方法 Research method	排放区间 Emission range (mg·m^-1·h^-1)	年总排放量 Total annual emissions (g·m^-1·a^-1)	参考文献 Reference
芬兰 Finland	雨养泥炭沼泽 Bog	静态箱 Static chamber	0.038-1.403	3.3	Nyk?nenet al., 1998
芬兰 Finland	矿养泥炭沼泽 Fen	静态箱 Static chamber	0.013-16.016	11.4	Nyk?nenet al., 1998
中国神农架 Shennongjia, China	雨养泥炭沼泽 Bog	涡度相关 Eddy covariance	-0.337-1.340	4.2	Chen et al., 2020
中国鄂西南 Southwest Hubei, China	雨养泥炭沼泽 Bog	静态箱 Static chamber	0.022-1.474	3.4	本研究 This study

Fig. 8 Average methane emission fluxes from different cover types of the Sphagnum bogs. B, bare land plot; P, Polytrichum commune plot; S, Sphagnum paluster plot.

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