Flood effect on CH₄ emission from the alas in Central Yakutia, East Siberia

Figures & data

Figure 1 Study site location.

Table 1 Annual air temperature and precipitation

Year	Average air temperature (°C)												Annual temperature
	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
2006	−42.9	−35.4	−21.1	−3.7	7.5	17.3	18.6	15.9	7.0	−8.3	−25.4	−35.4	−8.8
2007	−30.4	−36.5	−18.6	−1.7	9.0	16.5	16.7	16.7	7.0	−4.9	−25.6	−32.6	−7.0
2008	−37.8	−30.1	−12.8	−5.5	10.0	19.2	20.3	16.7	5.4	−3.9	−26.8	−40.1	−7.1
2009	−34.0	−37.2	−18.8	−3.3	7.6	19.5	20.5	15.2	7.8	−5.3	−28.7	−36.2	−7.7
100 years average†	−40.7	−35.5	−21.7	−6.2	6.7	15.7	19.0	15.1	6.2	−8.0	−28.3	−38.9	−9.7
Year	Monthly precipitations (mm)
	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec	Annual precipitations
2006	3	4	4	1	11	13	27	151	54	14	35	9	326
2007	22	4	5	16	22	39	63	37	30	26	16	8	288
2008	16	9	21	11	5	16	50	41	34	34	13	10	260
2009	6	1	12	5	29	3	26	46	27	33	6	3	197
100 years average†	9	7	6	8	18	29	39	39	26	18	14	10	223

Gray color: summer period from May to September; †: Average for last 100 years.

Figure 2 Spatial distribution of the studied thermokarst depression each July from 2006 to 2009.

Table 2 Inter-annual fluctuation of biome spatial distributions in the studied thermokarst depression

	2006	2007	2008	2009
Locations (biomes)	Area (ha)
Dry grassland	19.2	17.1	11.1	10.7
Wet grassland	24.1	3.3	6.2	8.7
Lake	20.4	43.3	46.5	44.4
(Lake vegetation area†)	(10.2)	(26.0)	(23.2)	(17.7)
Total depression area	63.7	63.7	63.7	63.7

†: lake vegetation area was included in the lake area.

Figure 3 Scheme of bubble traps. (a) summer trap; (b) winter trap.

Table 3 Cumulative values of diffusion methane (CH₄) flux from different locations and measurement years during the measurement period (April–October) [mean ± standard deviation (SD) of different months]

Location	Cumulative CH4 flux (kg C ha^−1)
	2006*	2007*	2008*	2009*
Forest	−0.56 ± 0.09	−0.34 ± 0.14	−1.04 ± 0.18	−0.88 ± 0.21
Dry grassland	−0.07 ± 0.07	−0.11 ± 0.11	0.26 ± 0.31	0.15 ± 0.12
Wet grassland	1.72 ± 1.31	2.99 ± 0.63	397 ± 240	4.89 ± 0.81
Lake water	140 ± 90	56.8 ± 44.9	284 ± 169	250 ± 195

C: carbon. Asterisks (*) indicate significant differences among measurement locations, and years [P < 0.05, two-way analysis of variance (ANOVA)].

Table 4 Cumulative methane (CH₄) flux via plant body and its contribution to the whole ecosystem CH₄ emission [mean ± standard deviation (SD)]

Location	Year	Diffusion flux (kg C ha^−1)	Whole ecosystem flux† (kg C ha^−1)	Flux via plant body (kg C ha^−1)	Contribution to the whole ecosystem emission (%)
Wet	2007	2.99 ± 0.61	17.40 ± 1.39	14.4	82.8
grassland	2008	397 ± 240	313 ± 319	−84.3	−27.0
	2009	4.89 ± 0.82	33.49 ± 22.52	28.6	85.4
Water*	2007	56.8 ± 44.9	143 ± 66	86.5	60.4
	2008	284 ± 169	458 ± 500	175.1	38.1
	2009	250 ± 195	2406 ± 1018	2155.2	88.4

C: carbon. Asterisks (*) indicate significant differences among locations [P < 0.05, two-way analysis of variance (ANOVA)]. †: Whole ecosystem flux including soil-water and plant body flux. Flux via plant body = whole ecosystem flux – diffusion flux. Contribution given in % of flux via plant body to the whole ecosystem flux.

Table 5 Averaged methane (CH₄) concentration in bubble and air volume in traps during winter and summer times of measurement and emission from lake water surface via ebullition [mean ± standard deviation (SD)]

	CH4 concentration (g C m^−3)			Ebullition rate of air (mL m^−2 day)			CH4 emission via ebullition (kg C ha^−1)
Season	Edge	Middle	Center	Edge	Middle	Center	Edge	Middle	Center	Average
Summer (Jul.–Sep., 3 months)*	3.7 ± 2.3	14.6 ± 5.3	13.7 ± 3.2	282.9 ± 2.2	282.9 ± 2.1	237.1 ± 2.4	5.12 ± 2.2	4.11 ± 2.1	2.99 ± 2.4	4.07 ± 1.1
Winter (Oct.–Apr., 7 months)	9.9 ± 3.5	11.0 ± 4.1	10.1 ± 6.5	20.9 ± 0.1	13.6 ± 0.1	7.5 ± 2.6	5.11 ± 0.1	5.11 ± 0.1	3.24 ± 2.6	4.48 ± 1.1
Other season (May and June, 2 months)*	–	–	–	–	–	–	1.3	1.3	1.3	1.3
Total annual ebullition	–	–	–	–	–	–	11.5 ± 2.2	10.5 ± 1.9	7.5 ± 1.1	9.9 ± 1.6

C: carbon; *: significant difference of CH₄ between seasons (winter–summer) and locations at P < 0.05.

Table 6 Emission of methane (CH₄) from thermokarst depression during 2006–2009. Different location values given in Mg carbon (C) area⁻¹ (%: contribution of total emission)

	2006			2007			2008			2009
	Area	CH4 emission		Area	CH4 emission		Area	CH4 emission		Area	CH4 emission
Locations	ha	Mg C area^−1	%	ha	Mg C area^−1	%	ha	Mg C area^−1	%	ha	Mg C area^−1	%
Dry grassland	19.2	−0.0013	−0.02	17.1	−0.0019	−0.04	11.1	0.0029	0.01	10.7	0.0016	0.00
Wet grassland	24.1	0.0415	0.73	3.3	0.0098	0.19	6.2	2.444	12.16	8.7	0.0423	0.08
Wet grassland, via plant body†	[24.1]	0.219‡	3.85	[3.3]	0.047	0.91	[6.2]	---	---	[8.7]	0.247	0.50
Lake	20.4	2.85	50.03	43.3	2.46	47.30	46.5	13.17	65.52	44.4	11.11	22.18
Lake, via plant body†	[10.2]	2.36‡	41.64	[26.0]	2.25	43.22	[23.2]	4.06	20.20	[17.7]	38.25	76.35
Lake, ebullition†	[20.4]	0.199§	3.49	[43.3]	0.422§	8.12	[46.5]	0.453§	2.26	[44.4]	0.433	0.86
Total CH4 emission		5.7	100		5.2	100		20.1	100		50.1	100

†: area of “wet grassland, via plant body” was included in area of “wet grassland”, and areas of “lake, via plant body” and “lake, ebullition” were also included in area of “lake”; ‡: estimated by using average of contribution rate of CH₄ flux via plant body in other years (2007–2009, except for 2008 in wet grassland) and diffusive flux measured in 2006; §: estimated by multiplying the ratio of ebullition to diffusive CH₄ emission measured in 2009 by diffusive CH₄ emissions of each year.