We aerobically incubated soil samples from a polygon center (P3, 72° 22.5 N, 126° 29.4 E) on Samoylov, Northeast Siberia for 150 days. We used three soil layers ((i) surface active layer, (ii) bottom active layer, (iii) permafrost), three different temperatures ((i) 1°C, (ii) 4°C, (iii) 8°C), and two treatments ((i) control without substrate addition, (ii) amended with 13C labeled Carex aquatilis. For each sample we used 4 aliquots. CO2 production was measured via gas chromatography. The isotopic signature of the produced CO2 was measured via isotope-ratio mass spectrometry. To differentiate between soil organic matter- (SOM-) and Carex-derived CO2 in amended samples, we used an isotopic mixing model. In control incubations all CO2 is SOM-derived.
