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 CO 2 , CH 4 , and N 2 O emissions and aboveground and belowground biomass variations. The high CO 2 flux from the nfP and fP sites and the low CO 2 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 CH 4 ha À1 yr À1 , whereas the almost zero CH 4 emission from the Phalaris plots and the BS site was due to the high S concentration in peat, which probably inhibited methanogenesis. The N 2 O flux varied from <0.1 kg on the Phalaris plots and the NB to 2.64 kg N 2 O ha À1 yr À1 on the FM. The highest yield of RCG was obtained in autumn (13.9 t and 8.0 t dw ha À1 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 À1 , respectively.The C balance of nfP and fP plots was negative in comparison to the BS (À3322, À5983, and 2504 kg CO 2 ha À1 yr À1 , 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 À5981 and À3885 kg CO 2 eq ha À1 yr À1, respectively. The BS site had a total GWP of 2544 kg CO 2 eq ha À1 yr À1 .

In northern countries, Lolium perenne L. generally survives poorly when grown inland and north of 60°N because of extensive winter damage. With the projected future climate change, it could become a promising option for improving production efficiency of the agricultural sector in these regions. Here, we compare the biomass production potential of cultivars of diverse origin across five locations stretching from Estonia to Iceland over a period of three harvest years, and their freezing tolerance under artificial conditions. The aim was to relate the observed pattern of adaptation to the geographic origin of the cultivars and their response to prevailing agroclimatic conditions. Significant interactions were observed between cultivars and test environments (locations × years), and significant interactions between cultivars and years were detected at four of the five locations. Models of joint regression, additive main effects and multiplicative interaction (AMMI) and factorial regression using several agroclimatic indices showed that cultivars developed in northern countries showed greater yield potential across the test environments and were, thus, generally better adapted than cultivars from Central Europe. Diploid cultivars were more frost tolerant than tetraploid cultivars giving them an advantage in locations which were characterized by low temperatures during the hardening period in autumn and mild and rainy winters, such as at the Icelandic location. Only a few cultivars showed general adaptability to the environmental conditions at the test sites, the most stable cultivar being an admixture of diploids and tetraploids. In future breeding, the best strategy would be to hybridize cultivars developed in northern countries with more exotic materials that combine high yield potential, adequate winter survival and superior disease resistance under northern conditions.

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