Net soil carbon balance in afforested peatlands and separating autotrophic and heterotrophic soil CO<sub>2</sub> effluxes

Abstract. Peatlands are a significant global carbon (C) store, which can be compromised by drainage and afforestation. Quantifying the rate of C loss from peat soils under forestry is challenging, as soil CO2 efflux includes both produced heterotrophic decomposition tree roots associated fungal networks (autotrophic respiration). We experimentally terminated autotrophic below-ground respiration in replicated forest plots cutting through all living (trenching) measured surface flux, litter input, decay rate, temperature moisture over 2 years. Decomposition cut was fluxes were corrected for this, resulted large change fraction : suggesting that even years after trenching decaying root biomass makes contributions to flux. Annual (heterotrophic flux) 115 ± 16 g m−2 yr−1, representing ca. 40 % total respiration. needle accelerated presence an active rhizosphere, indicating priming effect labile inputs roots. This suggests our estimates mineralization trenched conservative underestimate overall rates loss. Considering also input trees, results indicate these 30-year-old drained afforested peatlands net sink C, since substantially more enters organic matter than decomposed heterotrophically. study does not account fluvial fluxes, represent small flux compared efflux; further, exudate deposition could source only partially sampled approach, adding plantations being potential sink. However, balance should taken lifespan order determine if sustained or become longer periods forestry.