The stable carbon isotope ratio (δ13C) is a key tool in tracing the source of carbon within and across ecosystems. In isotope mixing models dissolved organic carbon (DOC) from terrestrial sources is often assigned a fixed δ13C of roughly -28‰ to -27‰ in C3 plant-dominated areas. However, the claim of a uniform δ13C distribution for terrestrial DOC sources of different reactivity has seldom been tested. We leached DOC from 40 sources in the Fennoscandinavian boreal forest, including four decay stages of litter from five dominant species and three organic soil types. Additionally incubations were applied in combination with the Keeling plot method to resolve the δ13C of the labile DOC. The results show a clear split between litter derived (~-32‰) and wetland soil derived DOC (~-26‰). Furthermore the labile subfraction of litter derived DOC was relatively deplete in 13C compared with bulk DOC while in wetland soils the labile pool has a relatively heavier 13C signature. As a result both sources show a labile pool comparable to the initial 13C values of ~-32‰ and ~-26‰ respectively, while the resistant pools of DOC show equal 13C values around ~-27.5‰. Chemical measurements of pre- and post-incubation DOC show clear differences between labile pools of DOC from different sources, indicative of different fractionation processes contributing to the differences seen in 13C values of the respective labile pools. These results suggest that the use of 13C mixing models might lead to misjudging the true amount of terrestrial derived - and in particularly labile - DOC within boreal aquatic systems.
|Number of pages||1|
|Publication status||Published - 2018|
|Event||ASLO Summer Meeting 2018 - Victoria, Canada|
Duration: 2018 Jun 10 → 2018 Jun 15
|Conference||ASLO Summer Meeting 2018|
|Period||2018/06/10 → 2018/06/15|