CH₄ emission from different stages of thermokarst formation in Central Yakutia, East Siberia

Figures & data

Figure 1 Stages of thermokarst formation in Central Yakutia (after Bosikov 1991). The main feature of this region is the underground ice-wedge complex.

Figure 2 Thermokarst landscape of the taiga forest in Central Yakutia.

Figure 3 Location map of the study region. The highlighted figure is the lowland region of Central Yakutia. The study sites are located between the Lena and Aldan rivers.

Figure 4 Different stages of thermokarst: I, Bullar; II, Dyede; III, Tuumpu; IV, mature Alas. The observation plots are shown in the photographs with arrows.

Table 1 Parameters for estimation of CH4 storage in the permafrost layer

Layer	Depth (m)	Thickness (m)	Type	Volumetric soil or ice content in the ground (%)	Air bubble ratio in soil (or ice) (%)	CH4 concentration in air bubble (p.p.m.v.)	CH4 storage at each layer (mg C m^−2)	Total CH4 storage mg C m^−2 (g C m^−2)
Active layer	0–1.2	1.2	–	–	–	–	–	259 (0.259)
Upper permafrost	1.2–3.0	1.8	Frozen soil	50	5	2,000	48.4
			Ice wedge	50	5	1,500	36.3
Lower permafrost	3.0–15.0	12	Frozen soil	50	5	1,000	161
			Ice wedge	50	5	80	12.9
Air pressure in the bubbles was assumed to be 1 atm. Data source: Brouchkov and Fukuda 2002.

Table 2 Soil temperature (5 cm) and soil moisture (0–5 cm) at each measurement

Ecosystem	Location	Soil or water temperature (°C)		Soil moisture (m^3 m^−3)
		6/15/2007	8/14/2007	6/15/2007	8/14/2007
Forest	Stage II	6.9 ± 0.9	15.5 ± 0.2	0.28 ± 0.005	0.05 ± 0.008
	Stage III	7.1 ± 0.2	13.5 ± 0.4	0.36 ± 0.009	0.15 ± 0.006
	Stage IV	8.0 ± 0.5	16.9 ± 0.3	0.28 ± 0.019	0.08 ± 0.003
Grassland	Stage I, on polygon	16.0 ± 0.5	22.2 ± 1.2	0.36 ± 0.009	0.33 ± 0.039
	Stage I, between polygon	11.2 ± 3.0	18.6 ± 0.3	0.41 ± 0.015	0.38 ± 0.004
	Stage II, near the pond	16.9 ± 0.9	22.8 ± 0.8	0.39 ± 0.009	0.39 ± 0.005
	Stage IV, dry	17.0 ± 0.5	21.0 ± 1.1	0.21 ± 0.012	0.07 ± 0.034
	Stage IV, near the pond	18.3 ± 0.1	19.4 ± 0.5	0.41 ± 0.007	0.41 ± 0.003
Pond	Stage II	18.0^†	26.2^†	–	–
	Stage III	18.6^†	21.2^†	–	–
	Stage IV	19.3^†	24.0^†	–	–
Values indicate mean ± standard deviation. ^†Water temperature.

Table 3 CH4 fluxes from different thermokarst stages and measurement times (June and August)

Type of CH4 flux	Ecosystem	Plot	CH4 flux (μg C m^−2 h^−1)		Difference
			6/15/2007	8/14/2007	Plots	Measurement times
CH4 emission from soil (or water) surface	Forest	Stage II	−12 ± 2.9	−34 ± 7.8	a	ns
		Stage III	−16 ± 6.5	−1.3 ± 1.5	b
		Stage IV	−14 ± 6.2	−26 ± 13	ab
	Grassland	Stage I, on polygon	0.9 ± 2.4	−5.4 ± 7.1	a	*
		Stage I, between polygon	13 ± 14	11 ± 12	a
		Stage II, near the pond	3.6 ± 6.0	11 ± 12	a
		Stage IV, dry grassland	0.7 ± 4.4	−9.1 ± 5.3	a
		Stage IV, near the pond	104 ± 2.9	285 ± 71	b
	Pond	Stage II	700 ± 194	8.0 × 10^3 ± 4.3 × 10^3	a	ns
		Stage III	657 ± 72	1.7 × 10^3 ± 1.3 × 10^3	a
		Stage IV	3.3 × 10^3 ± 5.3 × 10^3	4.1 × 10^3 ± 2.5 × 10^3	a
CH4 emission from whole ecosystem	Grassland and pond	Stage II, near the pond	54 ± 57	241 ± 250	–	–
		Stage IV, near the pond	308 ± 59	1.9 × 10^3 ± 167	–
		Stage II, pond	190 ± 48	4.3 × 10^4 ± 3.0 × 10^4	–
		Stage IV, pond	1.4 × 10^3 ± 410	1.7 × 10^4 ± 8.6 × 10^3	–
Values indicate mean ± standard deviation. Asterisks (*) and letters indicate significant differences between measurement times and among plots, respectively, within the same ecosystem (P < 0.05, two-way ANOVA; ns, not significant).

Figure 5 Relationship between CH4 flux and (a) soil moisture or volumetric soil water content and (b) soil temperature (°C) at the forest (F) and grassland (G) sites. NS, not significant.

Table 4 CH4 emission via plants and its contribution to CH4 emission from the whole ecosystem at wet locations (wet grassland near the pond and pond water surface)

Ecosystem	Plot	CH4 emission via plants (μg C m^−2 h^−1)		Contribution (%)
		6/15/2007	8/14/2007	6/15/2007	8/14/2007
Wet grassland	Stage II, near the pond	50 ± 31	230 ± 131	93	95
	Stage IV, near the pond	203 ± 31	1.7 × 10^3 ± 119	66	85
Pond	Stage II	NA	3.5 × 10^4 ± 1.7 × 10^4	NA	81
	Stage IV	NA	1.3 × 10^4 ± 5.5 × 10^3	NA	76
Values indicate mean ± standard deviation. The emission via plants was calculated as the difference between the measurements with and without vegetation plots in considered locations. NA, data is not available because the CH4 emission from the soil or water surface was higher than the CH4 emission from the whole ecosystem.

Table 5 CH4 flux from different boreal ecosystems

Location	Latitude/Longitude	Permafrost presence	Ecosystem type	CH4 flux (μg C m^−2 h^−1)	Reference
Forest
Central Yakutia, Russia	62°19′N, 129°30′E	Yes	Larch forest	−17 to −3.4	Morishita et al. (2003) & Takakai et al. (2008)
Central Yakutia, Russia	62°11′ N, 130°33′E	Yes	Larch forest	−34 to−1.3	This work
Asa, South Sweden	57°08′ N, 14°45′E	No	Spruce forest	−15 to 22	von Arnold et al. (2005)
West Siberia, Russia	56°52′ N, 83°17′E	Yes	Birch–Pine forest	−283 to −91	Nakano et al. (2006)
Grizedale, UK	54°59′N, 1°30′E	No	Larch forest	−98 to −89	Bradford et al. (2000)
Dry grasslands
Central Yakutia, Russia	62°54′N, 130°33′E	Yes	On polygon, Bullar	−5.4 to 0.9	This work
Central Yakutia, Russia	62°19′ N, 129°30′E	Yes	Dry grassland, mature Alas	−28 to 4.8	Morishita et al. (2003) & Takakai et al. (2008)
Central Yakutia, Russia	62°08′N, 130°30′E	Yes	Dry grassland, mature Alas	−9.1 to 0.7	This work
Wet grasslands
North East Siberia, Russia	68°N, 161°E	Yes	Tundra, tussock	6.3 × 10^3 to 9.4 × 10^3	Corradi et al. (2005)
Smith Lake, Alaska	64°52′N, 147°51′W	Yes	Tundra, on tussock	45 to 325	Whalen and Reeburgh (1992)
Smith Lake, Alaska	64°52′N, 147°51′W	Yes	Tundra, between tussock	62 to 2.0 × 10^3	Whalen and Reeburgh (1992)
Smith Lake, Alaska	64°52′N, 147°51′W	Yes	Tundra, edge of pond	8.7 to 2.7 × 10^4	Whalen and Reeburgh (1992)
Central Yakutia, Russia	62°54′N, 130°33′E	Yes	Stage I, between polygon	11 to 12	This work
Central Finland	62°49′N, 30°59′E	Yes	Fen grassland	8.3 × 10^3 to 2.5 × 10^4	Nykänen et al. (1995)*
Central Yakutia, Russia	62°19′N, 129°30′E	Yes	Mature Alas (Stage IV), edge of pond	2.2 × 10^3 to 4.8 × 10^3	Morishita et al. (2003)
Central Yakutia, Russia	62°19′N, 129°30′E	Yes	Mature Alas (Stage IV), edge of pond	4.3 × 10^3 to 4.1 × 10^4	Takakai et al. (2008)*
Central Yakutia, Russia	62°11′N, 130°33′E	Yes	Stage II, near the pond	4 to 241	This work*
Central Yakutia, Russia	62°08′N, 130°30′E	Yes	Stage IV, near the pond	104 to 2.0 × 10 ^3	This work*
Pond without vegetation
East Siberia, Russia	69°N, 161°E	Yes	Tundra, pond	237	Zimov et al. (1997)
West Siberia, Russia	65°52′N, 74°58′E	Yes	Tundra, pond	253 to 392	Repo et al. (2007)
Central Yakutia, Russia	62°19′N, 129°30′E	Yes	Mature Alas (Stage IV), pond	600 to 2.4 × 10^3	Morishita et al. (2003)
Central Yakutia, Russia	62°11′N, 130°33′E	Yes	Stage II, pond	700 to 8.1 × 10 ^3	This work
Central Yakutia, Russia	62°11′N, 130°34′E	Yes	Stage III, pond	654 to 1.7 × 10 ^3	This work
Central Yakutia, Russia	62°08′N, 130°30′E	Yes	Stage IV, pond	3.3 × 10 ^3 to 4.1 × 10 ^3	This work
West Siberia, Russia	60°59′N, 70°10′E	Yes	Tundra, pond	1.0 × 10^3 to 5.0 × 10^3	Repo et al. (2007)
Positive values of CH4 flux indicate net emission from the ecosystem and negative values indicate net uptake from the atmosphere. The asterisk (*) indicates CH4 flux from the whole ecosystem, including the soil and via plants.

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