Concentration and δD of molecular hydrogen in boreal forests: Ecosystem-scale systematics of atmospheric H2

We examined the concentration and δD of atmospheric H2 in a boreal forest in interior Alaska to investigate the systematics of high latitude soil uptake at ecosystem scale. Samples collected during nighttime inversions exhibited vigorous H2 uptake, with concentration negatively correlated with the concentration of CO2 (−0.8 to −1.2 ppb H2 per ppm CO2) and negatively correlated with δD of H2. We derived H2 deposition rates of between 2 to 12 nmol m−2 s−1. These rates are comparable to those observed in lower latitude ecosystems. We also derive an average fractionation factor, α = D:Hresidual/D:Hconsumed = 0.94 ± 0.01 and suggestive evidence that α depends on forest maturity. Our results show that high northern latitude soils are a significant sink of molecular hydrogen indicating that the record of atmospheric H2 may be sensitive to changes in climate and land use.