Determination of respiration and photosynthesis fractionation factors for atmospheric dioxygen inferred from a vegetation–soil–atmosphere analogue of the terrestrial biosphere in closed chambers

Abstract. The isotopic composition of dioxygen in the atmosphere is a global tracer which depends on biosphere flux toward and from (photosynthesis respiration) as well exchanges with stratosphere. When measured fossil air trapped ice cores, relative concentration 16O, 17O, 18O O2 can be used for several applications such core dating past productivity reconstruction. However, there are still uncertainties about accuracy these tracers they depend integrated discrimination different biological processes production uptake, we currently have very few independent estimates. Here determined respiration photosynthesis fractionation factors atmospheric experiments carried out replicated vegetation–soil–atmosphere analogue terrestrial closed chambers growing Festuca arundinacea. values during soil dark leaves equal to -12.3±1.7 ‰ -19.1±2.4 ‰, respectively. In chambers, also found value attributed photosynthetic +3.7±1.3 ‰. This last estimate suggests that contribution Dole effect may been underestimated previous studies.