Soil organic carbon and CO2 respiration at subzero temperature in soils of Arctic Alaska

Carbon dioxide respiration rates were measured in the laboratory at −2°C for 88 arctic Alaska soil horizon samples. Soil horizon samples represented most ATLAS C‐flux study sites to a 1‐m depth. Sites represented extend across the Alaska Arctic, from tundra at Prudhoe Bay (70°N, 149°W) in the northeast to the tundra–forest transition zone of the Seward Peninsula (64°N, 163°W) in the southwest, a range of nearly 1000 km. Results of an initial temperature sensitivity study indicated that at 4°C, organic horizons (>20% organic carbon [OC]) have average respiration rates that are twice as high as those found for the mineral horizons. However, as temperature dropped to −2°C, respiration in organic horizons was about the same as that for the low OC mineral horizons (with