## 3 Results and Discussion
#### 3.2.1 Relationships between Daily Precipitation and CO\({}_{2}\) Flux Anomalies  
Analysis showed that abundant precipitation mainly leads to increased CO\({}_{2}\) emissions (Figure 3b) in savannas: during 25-37% of the days with extreme precipitation (exceeding 95% quantile), the positive anomalies of CO\({}_{2}\) fluxes exceeded 1 STD. This trend was confirmed by the inverse relationship: 18-22% of the days with CO\({}_{2}\) flux anomalies higher than 1 STD corresponded to the days with extreme (>95% quantile) precipitation (Figure 5b). Figure 6: The same as Figure 5 but for tropical evergreen, deciduous needle leaf, tropical rain, and dry or seasonal forests. This was due to the watering of the soil horizons and was a consequence of the increased activity of soil biota resulting in increased CO2 emissions from the soil surface. An exception to this rule was the station Au-RDF located in the north of Australia, where the extreme precipitation almost equally entailed strong positive and negative CO2 flux anomalies (Figure 3b). This may have been due to limited soil organic carbon stocks, leading to reduced soil respiration, as well as the rapid response of the photosynthetic apparatus of plants to increased water availability in the root zone. Noteworthy, this station was very close to the AU-Dry station, where the increase in CO2 emissions was only connected with abundant precipitation (Figure 1). Precipitation deficit in savannas led to an increase in CO2 uptake on the African continent: negative CO2 flux anomalies exceeding 1 STD occurred within 28-100% of days, with daily rainfall below 5% (Figure 3d). Half of the days with CO2 flux anomalies lower than \(-1\) STD (50%) coincided with precipitation amounts lower than 5% quantile in Sahel (SN-Dhr). At the other stations, the percentage was much lower (Figure 5d). On the other continents, the relationship \"increased CO2 uptake/precipitation deficit\" was not evident, and the CO2 flux anomalies did not exceed the STD during the days with the lack of precipitation. The increased CO2 uptake under dry conditions may have resulted from the combined effects of the reduced ER and non-significantly changed GPP in savanna ecosystems due to their adaptation to drought conditions. The water supply from deeper water layers may have been a key factor influencing the high rate of plant photosynthesis. This was despite the fact that the seasonal GPP variations in semi-arid ecosystems were mainly controlled by near-surface soil water [52; 53]. An increase in CO2 release in evergreen broadleaf forests was associated with extreme precipitation over 20-30% of days (Figure 4b), resulting from soil wetting and intensive soil respiration. This was the main feature of all analyzed flux stations located in evergreen tropical rainforests on different continents. A lack of precipitation (Figure 4d) led to an increase in CO2 uptake (16-23% of days). The latter may have been due to the increase in GPP values at high solar radiation (during the days without precipitation and clouds) and optimal soil moisture conditions that remained in evergreen forests even in the absence of precipitation. The inverse relationship was significant for positive CO2 flux anomalies that often were accompanied by heavy rainfall (Figure 6b) but was not significant for negative anomalies that were observed with no relevance to the precipitation extremes (Figure 6d). In tropical rainforests (e.g., flux station in South East Asia--BNS), the relationships between precipitation and CO2 fluxes were less evident, and the extreme precipitation usually did not correspond to the anomalies of CO2 fluxes. The grasslands and permanent wetlands were characterized by the response of CO2 fluxes to the precipitation variability, similar to rainforests (Figure 3b,d): the strong CO2 release resulting from heavy rainfall (up to 33% of the days) and increased CO2 uptake associated with the lack of precipitation (up to 25% of the days).