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CO2, CH4 and N2O fluxes of upland black spruce (Picea mariana) forest soils after forest fires of different intensity in interior Alaska
Authors:Tomoaki Morishita  Kyotaro Noguchi  Yongwon Kim  Yojiro Matsuura
Affiliation:1. Shikoku Research Center, Forestry and Forest Products Research Institute (FFPRI), 2–915 Asakuranishimachi, Kochi, Kochi 780–8077, Japanmorisita@affrc.go.jp;3. FFPRI, 1 Matsunosato, Tsukuba, Ibaraki 305–8687, Japan;4. International Arctic Research Center, University of Alaska Fairbanks, 930 Koyukuk Dr., Fairbanks, AK 99775–7335, USA
Abstract:Abstract

Forest fires can change the greenhouse gase (GHG) flux of borea forest soils. We measured carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O) fluxes with different burn histories in black spruce (Picea mariana) stands in interior Alaska. The control forest (CF) burned in 1920; partially burned (PB) in 1999; and severely burned (SB1 and SB2) in 2004. The thickness of the organic layer was 22 ± 6 cm at CF, 28 ± 10 cm at PB, 12 ± 6 cm at SB1 and 4 ± 2 cm at SB2. The mean soil temperature during CO2 flux measurement was 8.9 ± 3.1, 6.4 ± 2.1, 5.9 ± 3.4 and 5.0 ± 2.4°C at SB2, SB1, PB and CF, respectively, and differed significantly among the sites (P < 0.01). The mean CO2 flux was highest at PB (128 ± 85 mg CO2-C m?2 h?1) and lowest at SB1 (47 ± 19 mg CO2-C m?2 h?1) (P < 0.01), and within each site it was positively correlated with soil temperature (P < 0.01). The CO2 flux at SB2 was lower than that at CF when the soil temperature was high. We attributed the low CO2 flux at SB1 and SB2 to low root respiration and organic matter decomposition rates due to the 2004 fire. The CH4 uptake rate was highest at SB1 [–91 ± 21 μg CH4-C m?2 h?1] (P < 0.01) and positively correlated with soil temperature (P < 0.01) but not soil moisture. The CH4 uptake rate increased with increasing soil temperature because methanotroph activity increased. The N2O flux was highest [3.6 ± 4.7 μg N2O-N m?2 h?1] at PB (P < 0.01). Our findings suggest that the soil temperature and moisture are important factors of GHG dynamics in forest soils with different fire history.
Keywords:Alaska  CH4  CO2  forest fire  N2O
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