Reed canary grass cultivation mitigates greenhouse gas emissions from abandoned peat extraction areas

We studied the impact of reed canary grass (RCG) cultivation on greenhouse gas emission in the following sites of an abandoned peat extraction area in Estonia: a bare soil (BS) site, a nonfertilized Phalaris (nfP) plot, a fertilized Phalaris (fP) plot, and a natural bog (NB) and a fen meadow (FM) as reference areas. The C balance and global warming potential (GWP) were estimated by measuring CO2, CH4, and N2O emissions and aboveground and belowground biomass variations. The high CO2 flux from the nfP and fP sites and the low CO2 emission from the BS are due to the enhancement of mineralization by plant growth on planted sites and inhibited mineralization by the recalcitrant C of BS. The NB site emitted 24 kg CH4 ha(-1) yr(-1), whereas the almost zero CH4 emission from the Phalaris plots and the BS site was due to the high S concentration in peat, which probably inhibited methanogenesis. The N2O flux varied from <0.1 kg on the Phalaris plots and the NB to 2.64 kg N2O ha(-1) yr(-1) on the FM. The highest yield of RCG was obtained in autumn (13.9 t and 8.0 t dw ha(-1) on the fP and nfP, respectively). By spring, the biomass yield on the fP and nfP plot was 12.7 and 7.9 t dw ha(-1), respectively. The C balance of nfP and fP plots was negative in comparison to the BS (-3322, -5983, and 2504 kg CO2 ha(-1) yr(-1), respectively). This indicates that the cultivation of RCG transformed them from a net source of C into a net sink of C. The GWP for the fP and nfP sites was -5981 and -3885 kg CO2 eq ha(-1) yr(-1), respectively. The BS site had a total GWP of 2544 kg CO2 eq ha(-1) yr(-1).