## 3 Results and Discussion
#### 3.2.4 Combined Effect of Temperature and Precipitation Extremes on Daily CO\({}_{2}\) Fluxes
Negative anomalies could be associated with an increase in savanna greenness and GPP, especially after the dry season [57]. Positive CO\({}_{2}\) flux anomalies were mainly the result of higher rates of heterotrophic and autotrophic respiration under elevated temperatures [58] and sufficient soil water supply [42]. It was notable that the high positive CO\({}_{2}\) flux anomalies occurred during hot/wet conditions with almost the same probability as during cold/wet periods in the savannas (Figure 7a,b). This confirmed the hypothesis of the dominant influence of precipitation and soil moisture content on CO\({}_{2}\) fluxes in the semiarid tropical regions. The hot/dry (HD) weather conditions had a maximum impact on the CO\({}_{2}\) fluxes in the tropical forests (evergreen, seasonal deciduous, and deciduous needle-leaf). During 22-100% of the days with extremely high temperatures and extremely low precipitations, increased CO\({}_{2}\) uptakes (anomaly exceeds \(-1\) STD) were found. These may have been the result of the very high GPP of tropical forests under sufficient soil moisture conditions. The reduced precipitation, in this case, was not a limiting factor in the optimal plant water supply. A similar effect of the hot/dry weather conditions on CO\({}_{2}\) fluxes occurred in the savanna in Congo (Figure 7c). However, in the Australian forest savanna (station AU-Dry), 30% of the days with HD conditions corresponded to the abnormally high CO\({}_{2}\) release. It was an interesting result because, according to an analysis of [PERSON] et al. [59], the soil CO\({}_{2}\) efflux in the northern Australian savanna during the most part of the dry season was much lower than the CO\({}_{2}\) efflux during the wet season. The very high CO\({}_{2}\) release under hot/dry weather conditions may have been due to the contribution of the forest canopy (reduced GPP and high ER) into the total CO\({}_{2}\) flux [60]. The effect of cold/dry (CD) anomalous weather events on CO\({}_{2}\) fluxes (during more than 20% of the days, the simultaneous CD and CO\({}_{2}\) flux anomalies were observed) was detected in several ecosystems in western Africa, northern Australia, the Malaysian peninsula, and Southern Africa. Negative anomalies prevailed, although there was one positive (AU-Fog). The effect of CD anomalies on CO\({}_{2}\) fluxes in other studied ecosystems was very small. The maximum negative CO\({}_{2}\) flux anomaly was found in Sahel (SN-Dhr) and the deciduous broadleaf forest in western Zambia in Africa (ZM-Mon) and was evidently connected with seasonal variations in GPP [61] and the adaptation of woody landscapes to dry conditions [62]. The positive CO\({}_{2}\) flux anomaly in a seasonal wetland in the wet-dry tropics of Northern Australia (AU-Fog) could be associated with variation in soil water content and groundwater depth, influencing GPP and ER [63]. The reduction in GPP under cold/dry anomalies while maintaining CO\({}_{2}\) emissions from the wetted peat may have been the main reason for this trend. It should be noted that the response of CO\({}_{2}\) fluxes to weather anomalies evidenced in our study was somewhat different from the previously documented relationships. [PERSON] et al. [8] evidenced that positive extremes in CO\({}_{2}\) fluxes were associated with dry and hot conditions in tropical forests. We detected the same CO\({}_{2}\) flux responses in Australian forest savannas, whereas higher CO\({}_{2}\) emission occurred during periods of extreme positive temperature anomalies in several types of evergreen and seasonal forests. However, the opposite feedback was revealed for most of the considered monitoring stations: intense CO\({}_{2}\) emissions, associated with cold/wet and hot/dry weather conditions, were accompanied by strong CO\({}_{2}\) uptakes.