Differences in surface roughness, energy, and CO2 fluxes in two moist tundra vegetation types, Kuparuk watershed, Alaska, USA

Roughly 70% of the tundra north of the Brooks Range, Alaska, can be classified as moist nonacidic (39%) and moist acidic tundra (31%). We investigated the differences in energy partitioning and carbon balance among these two important landscape types. Despite structural differences in plant growth forms, moss cover, and soil pH, the sensible and latent heat fluxes were quite similar. However, aerodynamic properties (i.e. roughness length), ground heat flux, and CO2 flux were significantly different: aerodynamic roughness of moist acidic tundra was 2.1 times higher than, and ground heat flux was 36% lower than the values obtained from moist nonacidic tundra. Daily carbon balance showed 26% more net CO2 uptake (with 34% greater ecosystem respiration and 30% greater gross primary production) in moist acidic tundra. The greater respiration rate in moist acidic tundra was explained by differences in surface soil temperatures, whereas the rate of gross primary production was only half of what was expected from observed differences in leaf area index. These differences suggest that understanding the controls of CO2 exchange in nonacidic moist tundra vegetation will be critical for determining the carbon budget of the Low Arctic region.