## 3 Results  
### Site General and Specific Climatology  
Our pine and larch sites were located in contrasting environments, in which the permafrost and cold soils of the larch site seemed to create a specific soil climate that was critical to control the carbon exchange. The descriptive long-term climatology of the annual and growing seasons of both sites is given in Table S1 (Supplementary File S3) based on the data of two weather stations: Tura (64.3\({}^{\circ}\) N and 102\({}^{\circ}\) E), located 20 km west of the larch site, and Sym (60.3\({}^{\circ}\) N and 87.8\({}^{\circ}\) E) located 30 km west of the pine site. The distance between these weather stations was about 650 km. Climatic data were derived from Reference books on climate (1965-1970) [45]. We compared the pre-1960 means found in these Reference books to the means we calculated for the 1960-1990 period, which was accepted as a baseline period in climate change studies. We found that the January temperature increased by 2-3 \({}^{\circ}\)C, the July temperature increased by 0.5 \({}^{\circ}\)C, and that annual precipitation increased by 10% on average at both sites [46]. We compared the January and July temperature and annual precipitation means for the baseline period of 1960-1990 and the means for the 1991-2009 period. We also compared the means for the years of eddy-covariance measurements 1998-2000 (Zotino site) and 2004-2008 (Tura site) and the means for the 1991-2010 period to typify how representative were the 3 and 4 years of our eddy-covariance measurements in two sites in the background of the two last decades (Figure S1, Supplementary File S3). The 1991-2009 period became warmer in both summer by 0.7 \({}^{\circ}\)C and winter by 1.3 \({}^{\circ}\)C in Sym (the pine site), especially in the north by 2.6 \({}^{\circ}\)C in Tura (the larch site). Precipitations increased in both study sites: only 11 mm/year (2%) in Sym and significantly 30 mm/year (7%) in dryer Tura. As for the periods of our eddy-covariance measurements, in Sym, the 1998-2000 period was 5 \({}^{\circ}\)C colder in winter and 80 mm/year dryer than during the 1991-2009 period; however, the summer was 0.6 \({}^{\circ}\)C warmer. In Tura, the 2004-2008 winter was 1 \({}^{\circ}\)C warmer, and summer was 0.7 \({}^{\circ}\)C cooler than during the 1991-2009 period; precipitation was 45 mm/year less (Table S1 and Figure S1, Supplementary File S3). The larch forest is in a cold, dry climate with very long, cold winters, which include a 40 cm snow pack. Summers are relatively warm but short, with low precipitation. The period with a positive temperature is 40% of the year span, of which 80% is the growing season which is accepted in ecological studies as the period when temperatures exceed the threshold of 5 \({}^{\circ}\)C. Cumulative degree days above 5 \({}^{\circ}\)C are only 845 \({}^{\circ}\)C, and negative degree days are extremely low, about \(-\)5000 \({}^{\circ}\)C. These climatic conditions result in a high continentality of climate characterized by a Conrad's index greater than 90. In turn, high continentality and low precipitation (slightly higher 300 mm yr\({}^{-1}\)) support continuous permafrost and low thawing (active) layer depths (ALD). Soils at the station Tura, under short grass cover, are not frozen at the surface during May-September, but stay frozen below a depth of 0.8 m prior to June and below a depth of 1.6 m prior to August and are never unfrozen at the 3.2 m depth. The pine forest exists in much milder conditions. Higher winter temperatures, longer growing seasons, warm soils with no permafrost, greater precipitation and a higher snow pack protecting soils from deep seasonal freezing and early thawing--all these climatic conditions favor the CO\({}_{2}\) exchange, higher carbon balance, and greater productivity of the pine forest in comparison to the larch forest.