## 3 Results
### Net Radiation, Energy Balance, Bowen Ratio and Water Balance
Precipitation (P), evaporation (E, calculated as LE/L), and the difference between them (P-E) (without considering water from thawed permafrost) for the growing season are shown in Figure 5 and Table 1.  
accumulating \(\sim\)80 mm and 100 mm of rain by the end of the season in the pine forest and in the larch forest, respectively (Figure 5). Figure 5: Monthly precipitation (P) and evaporation (E) (**left**) and cumulative water balance (P–E) for the growing seasons (**right**) in the dry year (2004) and in the wet year (2008) in the Gmelin larch and (1999) and (2000) respectively in the Scots pine ecosystems. Daily, Seasonal, and Annual Dynamics of Ecosystem CO\({}_{2}\) Exchange: NEE, R\({}_{eco}\), and GPP  
The daily dynamics of the ecosystem CO\({}_{2}\)-exchange have similar patterns in our larch and pine stands over all observational years, although their curve shapes were different due to day lengths and NEE values: more compressed in NEE and prolonged in the day span in the larch pattern and, conversely, extended and shortened in the pine pattern (Figure 6 upper). Night-time respiration turned to day-time CO\({}_{2}\) assimilation at 3-9 a.m. in the larch forest compared to 6-8 a.m. in the pine forest. In the summer, photosynthetic activities (PAR \(>\) 10 umol m\({}^{-2}\) s\({}^{-1}\)) in the larch forest lasted longer than in the pine forest due to longer light days at the 64\({}^{\circ}\) N latitude vs. 60\({}^{\circ}\) N latitude (the \(\varprojlim\) day\({}^{>}\) effect): 16-18 h vs. 14-15 h a day. In mid-July, daily maximal half-hourly CO\({}_{2}\) flux reached \(-\)(9-11) umol m\({}^{-2}\) s\({}^{-1}\) in the larch forest and \(-\)(10-12) umol m\({}^{-2}\) s\({}^{-1}\) in the pine forest (not shown). However, the average daily maximum CO\({}_{2}\) uptake in June and July was smaller in the larch ecosystem (4 umol m\({}^{-2}\) s\({}^{-1}\)) than in the pine forest (7 umol m\({}^{-2}\) s\({}^{-1}\)). Figure 6 upper). Thus, a longer day effect in the larch forest did not yield a larger daily total CO\({}_{2}\) uptake. In the mid-summer, June-July, NEE crossed the null at midnight, becoming a CO\({}_{2}\) source and at 4 am, becoming a CO\({}_{2}\)-sink in the larch forest (Figure 6 upper). In early September, when the needles started yellowing, the daily total NEE became about a null or changed to a positive sign (Figure 6 middle). At the summer peak, the pine forest became a CO\({}_{2}\) source from 9 p.m. to 6 a.m., which was 5 h longer than the larch forest was a CO\({}_{2}\) source. In October, NEE became positive and stayed such till April. In general, daily CO\({}_{2}\) exchange rates were about twice as large in the pine forest than in the larch forest (Figure 6 middle). In the larch ecosystem, NEE was \(-\)0.1 mol CO\({}_{2}\) m\({}^{-2}\) day\({}^{-1}\) at the beginning of the  
Figure 6: Daily (**upper**), seasonal (**middle**) and cumulative (**lower**) NEE in the Gmelin larch (**left**) and Scots pine (**right**) ecosystems for the growing season (May–September, V–IX). vegetation season in June, reached its maximum, \(-0.22\) mol m\({}^{-2}\) day\({}^{-1}\), in July, and crossed null again at the end of August. The pine ecosystem performed a greater NEE during the growing season, starting at 0-0.2 mol m\({}^{-2}\) d\({}^{-1}\) in May, reaching 0.2-0.3 mol m\({}^{-2}\) day\({}^{-1}\) in midsummer, and crossing null again at the end of September. In the Gmelin larch forest, seasonal NEP (-NEE integrated over a long period [39] accumulated for the growing season varied from 63 to 106 g C m\({}^{-2}\), with an average of \(\sim\)83 g C m\({}^{-2}\) season\({}^{-1}\) for 2004-2008 (Tables 2 and 3). Assuming that winter respiration in the cold environment of interior Siberia was low, we concluded that both ecosystems stayed a C-sink year-round of different strength, though.