It is important to quantify carbon decomposition to assess the reforestation impact on the forest floor C stocks. Estimating the loss of C stock in a short-term perspective requires measuring changes in soil respiration. This is not trivial due to the contribution of both soil microbes and vegetation to the measured CO₂ flux. However, C stable isotopes can be used to partition the respiration and potentially to assess how much of the recalcitrant C stock in the forest floor is lost. Here, we measured the soil respiration at two forest sites where different regeneration methods were applied, along with an intact forest soil for reference. In so doing, we used a closed dynamic chamber for measuring respiration and the 13C composition of the emitted CO₂. The chamber measurements were then supplemented with the soil organic carbon analysis and its δ¹³C content. The mean δ¹³C-CO₂ estimates for the source of the CO₂ were -26.4, -27.9 and -29.5‰, for the forest, unploughed and ploughed, respectively. The ¹³C of the soil organic carbon did, not differ significantly between sites. The higher soil respiration rate at the forest, as compared to the unploughed site, could be attributed to the autotrophic respiration by the forest floor vegetation.