Figure 2. Losses of native SOC from different horizons of arctic permafrost soils after 25 weeks of incubation (dark grey bars).

Losses induced by the addition of cellulose or protein in comparison to control samples are indicated in light grey. Bars represent means with standard errors, different letters indicate significant differences between horizons at p < 0.05. See Supplementary Fig. S1 for the development of SOC- and substrate-derived respiration over time.