Isoprene Fluxes from a Tundra Ecosystem

Whole-system fluxes of isoprene from a moist acidic tundra ecosystem and leaf-level emission rates of isoprene from an important species in that same ecosystem (Salix pulchra) were measured during two separate field campaigns to assess the contribution of biogenic volatile organic compounds on the chemistry of the Arctic atmosphere. The field campaigns were conducted during the summers of 2005 and 2010. The measurements took place in the Imnavait Creek watershed near the Toolik Field Station on the north slope of the Brooks Range (69° N, 149° W). The whole system fluxes were measured in conjunction with a project that is determining the net carbon exchange of the ecosystem (Arctic Observatory Network). Significant whole-system isoprene fluxes were observed during both campaigns. The maximum rate of isoprene flux measured was over 1 mg C m-2 hr with an air temperature of 22° C and a PAR level over 2000 μmol m-2 s-1. Leaf level isoprene emission rates for S. pulchra reached 20 nmol m-2 s-1 (38 μg C gdw -1 hr-1), which was over 1% of the net carbon assimilated. In addition, several moss species emitted significant amounts of isoprenes. These significant rates of isoprene emission need to be further investigated in field studies and will have major impacts of efforts to model tropospheric chemistry in the Arctic. Imnavait Creek AON flux tower