Carbon dioxide exchange between an old-growth forest and the atmosphere. Ecosystems 7:513–24

Eddy-covariance and biometeorological methods show significant net annual carbon uptake in an old-growth Douglas-fir64 forest in southwestern Washington, USA. These results contrast with previous assumptions that old-growth forest eco-systems are in carbon equilibrium. The basis for differences between conventional biomass-based carbon sequestration estimates and the biomete-orologic estimates are discussed. Annual net eco-system exchange was comparable to younger ecosystems at the same latitude, as quantified in the AmeriFlux program. Net ecosystem carbon uptake was significantly correlated with photo-synthetically active radiation and air temperature