Abstract:

The release of CO₂ from summer ice-free tundra of the high Arctic plays an important role in the global carbon cycle. These net ecosystem exchanges (NEEs) and their influence factors from Seabird Sanctuary Tundra (TSB), Tundra in Non-Seabird Colony (TNS) and Tundra in Transition Zone (TTR) were measured using the closed chamber method during the Fourth Arctic Scientific Exploration (26 July–5 August 2008) in the High Arctic. The spatial variations of NEE show that TSB was a sink for CO₂, with an average NEE of (−39.0±6.0) mg·m⁻²·h⁻¹_. Typically, absorption of CO₂ in areas with high vegetation cover and strong seabird usage was greater than in areas with lower vegetation cover and seabird usage. In contrast, TNS and TTR were emission sources for CO₂, with average NEEs of (12.0±6.3) mg·m⁻²·h⁻¹ and (40.5±29.3) mg·m⁻²·h⁻¹, respectively. Highland TTR ((106.4±23.1) mg·m⁻²·h⁻¹) was the strongest emission source, while peatland TTR [(−58.3±9.5) mg·m⁻²·h⁻¹] was a strong sink. Spatial variation of NEEs was linked to differences in vegetation cover and hydrological conditions related to seabird activity in all tundra types. Physical and chemical properties of tundra soils also affected NEE values, showing negative correlations with soil moisture (r=−0.44, P=0.003) in TSB and TNS, but a positive correlation with soil temperature (r=0.32, P=0.06) and negative correlations with NH₄⁺-N (P<0.05) and NO₃^–-N (P<0.05) concentrations in TSB.

Key words: CO₂, Net CO₂ fluxes, Arctic, Ny-?lesund, High Arctic tundra