CO 2 and CH 4 exchanges between moist moss tundra and atmosphere on Kapp Linné, Svalbard

[摘要] 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 netecosystem exchange (NEE) during the summer (9 June–31 August) was negative(sink), with − 0.139  ±  0.032  µ mol m −2  s −1 correspondingto − 11.8 g C m −2 for the whole summer. The cumulated NEE over the wholegrowing season (day no. 160 to 284) was − 2.5 g C m −2 . The CH 4 fluxduring the summer period showed a large spatial and temporal variability.The mean value of all 214 samples was 0.000511  ±  0.000315  µ mol m −2  s −1 , which corresponds to a growing season estimate of 0.04 to0.16 g CH 4  m −2 . Thus, we find that this moss tundra ecosystem isclosely in balance with the atmosphere during the growing season when regardingexchanges of CO 2 and CH 4 . The sink of CO 2 and thesource of CH 4 are small in comparison with other tundra ecosystems inthe high Arctic. Air temperature, soil moisture and the greenness index contributed significantly to explaining the variation in ecosystem respiration ( R eco ), while active layer depth, soil moisture and the greenness index were the variables that bestexplained CH 4 emissions. An estimate of temperature sensitivity of R eco and gross primary productivity (GPP) showed that the sensitivityis slightly higher for GPP than for R eco in the interval 0–4.5  ∘ C; thereafter, the difference is small up to about 6  ∘ C and then begins to rise rapidly for R eco . The consequence of this, for a small increase in air temperature of 1 ∘ (all other variables assumed unchanged), was that the respiration increasedmore than photosynthesis turning the small sink into a small source (4.5 g C m −2 ) during the growing season. Thus, we cannot rule out that thereason why the moss tundra is close to balance today is an effect of thewarming that has already taken place in Svalbard.

[学科分类] 大气科学