Moist moss tundra on Kapp Linne, Svalbard is a net source of CO2 and CH4 to the atmosphere

• Main Authors: Lindroth, Anders, Pirk, Norbert, Jónsdóttir, Ingibjörg S., Stiegler, Christian, Klemedtsson, Leif, Nilsson, Mats
• Format: Text
• Language: English
• Published: 2021
• Subjects: Arctic; Svalbard; Tundra
• Online Access: https://doi.org/10.5194/bg-2021-308; https://bg.copernicus.org/preprints/bg-2021-308/

We measured CO 2 and CH 4 fluxes using chambers and eddy covariance (only CO 2 ) from a moist moss tundra in Svalbard. The average net ecosystem exchange (NEE) during the summer (June–August) was −0.40 g C m −2 day −1 or −37 g C m −2 for the whole summer. Including spring and autumn periods the NEE was reduced to −6.8 g C m −2 and the annual NEE became positive, 24.7 gC m −2 due to the losses during the winter. The CH 4 flux during the summer period showed a large spatial and temporal variability. The mean value of all 214 samples was 0.000511 ± 0.000315 µmol m −2 s −1 which corresponds to a growing season estimate of 0.04 to 0.16 g CH 4 m −2 . We find that this moss tundra emits about 94–100 g CO 2 -equivalents m −2 yr −1 of which CH 4 is responsible for 3.5–9.3 % using GWP 100 of 27.9 respectively GWP 20 . Air temperature, soil moisture and greenness index contributed significantly to explain the variation in ecosystem respiration (R eco ) while active layer depth, soil moisture and greenness index were the variables that best explained CH 4 emissions. Estimate of temperature sensitivity of R eco and gross primary productivity showed that a modest increase in air temperature of 1 degree did not significantly change the NEE during the growing season but that the annual NEE would be even more positive adding another 8.5 g C m −2 to the atmosphere. We tentatively suggest that the warming of the Arctic that has already taken place is partly responsible for the fact that the moist moss tundra now is a source of CO 2 to the atmosphere.