## 3 Results and Discussion
### The Response of NEE and LE Fluxes to Extreme Precipitation
#### 3.2.1 Variation in NEE and LE Flux in Warm Season  
In almost all forest types considered in our study, heavy precipitation led to increased CO\({}_{2}\) emissions into the atmosphere (red bars in Figures 11-16). There was also a slight increase in the NEE anomaly with increasing precipitation (Figure S6.1). In the mixed evergreen needleleaf and broadleaf forests, up to 40-70% of days with extreme precipitation were associated with positive NEE anomalies above STD (Figures 11a and 12a). In deciduous forests, the percentage was slightly lower: 30-50% (Figure 12b). The observedresponse may be related to the well-known \"Birch effect\" [34], which is manifested by a strong CO\({}_{2}\) release after rewetting of dry soils, resulting from increased soil moisture and enhanced decomposition and mineralization rates. The prolonged effect of soil wetting on NEE fluxes was estimated using the API index. It was more often associated with strong negative NEE anomalies (blue bars) than with extreme daily precipitation. Although CO\({}_{2}\) emissions (red bars) exceeded CO\({}_{2}\) uptake (blue bars) in mixed (Figure 14a) and evergreen needleaf forests (Figure 13a), as well as in deciduous broadleaf and needleaf forests (Figure 15a), the difference between the percentage of days with positive and negative anomalies was rather small (between 2 and 20%). Negative and positive NEE anomalies were evenly distributed during days with extreme API values in evergreen broadleaf forests (Figure 14a). The increase in CO\({}_{2}\) uptake during the period following heavy precipitation (API in our study was calculated as the weighted total precipitation for the preceding 14 days) was due to intensified photosynthesis in living plants in the case of sunny weather and sufficient soil moisture conditions [78]. The precipitation deficit, represented by extremely low API values, was associated with high CO\({}_{2}\) uptake in most considered forest ecosystems. In the absence of prolonged soil drought, this trend demonstrated the high adaptive potential of the most temperate and boreal forest ecosystems to adapt to short-term (less than 14 days) periods without precipitation. Figure 11: The percentage of days when NEE and LE anomalies greater than 1 STD occurred simultaneously with extremely high precipitation during the warm (**a**) and cold (**b**) seasons in evergreen needleleaf forests (see text for details). The number of cases where the anomalies of precipitation and NEE/LE were observed on the same day is shown above the bars. Figure 12: The percentage of days when NEE and LE anomalies greater than 1 STD occurred simultaneously with extremely high precipitation during the warm (**a**,**b**) and cold (**c**) seasons in mixed and evergreen broadleaf forests (**a**), deciduous broadleaf and needleleaf forests (**b**), and mixed deciduous broadleaf and needleleaf forests (**c**) (see text for details). The number of cases where the anomalies of precipitation and NEE/LE were observed on the same day is shown above the bars. Figure 13: The percentage of days when NEE and LE anomalies greater than 1 STD occurred simultaneously with extremely high (**a**,**c**) and low (**b**,**d**) API during warm (**a**,**b**) and cold (**c**,**d**) seasons in evergreen needleleaf forests (see text for details). The number of cases where the anomalies of API and NEE/LE were observed on the same day is shown above the bars. Figure 14: The percentage of days when NEE and LE anomalies greater than 1 STD occurred simultaneously with extremely high (**a**) and low (**b**) API during the warm season in mixed and evergreen broadleaf forests (see text for details). The number of cases where the anomalies of API and NEE/LE were observed on the same day is shown above the bars. Figure 15: The percentage of days when NEE and LE anomalies greater than 1 STD occurred simultaneously with extremely high (**a**) and low (**b**) API during the warm season in deciduous broadleaf and needleleaf forests (see text for details).