## 2 Materials and Methods  
The Macao municipality (Santarem district, Portugal) has an area of approximately 40,000 ha (Figure 1). The climate of Macao is warm and temperate (according to the Koppen-Geiger classification), with a rainy winter, and a hot and dry summer. Yearly average temperature is 15.9 \({}^{\circ}\)C and total annual rainfall average is about 840 mm. The highest precipitation occurs in January with an average of 122 mm, while July is the driest month with an average of 7 mm. January is the coldest month with an average temperature of 9.3 \({}^{\circ}\)C, while the warmest is August with an average temperature of 23.6 \({}^{\circ}\)C [34]. The altitude in the Macao municipality ranges from 30 to 640 m, with steep slopes (over 30%) in many areas. The forested area of Macao is mainly occupied by highly combustible species, for example, _Eucalyptus globulus_ Labill., _Pinus pinaster_ Ait., and bush. Landsat 5 and 8 (NASA), and MODIS Terra (NASA) used in this study were obtained from the United States Geological Survey (USGS) Earth Explorer [35]. Images were acquired in 1991, 2003, 2017 and 2019, the years with major wildfires in the region: (i) on 24 and 26 June, 17 July, and 13 August 1991; (ii) on 25 June, 19 July, and 2 August 2003; and (iii) on 1 and 23 July, 16 August, and 23 September 2017. A short wildfire that occurred on 20 July 2019 was also included in this study because it affected areas unburned in 2017. Table 2 identifies imagery used to characterize the area burnt by these wildfires obtained from the  
Figure 1: Location of study area. (light brown) Santarem district; (dark brown) Macão municipality. area, NDVI values were reclassified into four classes (Table 5). This reclassification is an adaptation from the studies of [PERSON] and [PERSON] (2017), and [PERSON] et al. (2018). The severity of the fires was quantified on the basis of the normalized burn ratio (NBR). According to [PERSON] and [PERSON] (2017), this ratio relates the near-infrared (\(\rho_{\text{NIR}}\)) with the medium-infrared (\(\rho_{\text{MIR}}\)) bands and is calculated for pre- and postfire scenarios (Equation (2)). The severity of the fire (dNBR; Equation (3)) can be given by the difference between NBRBF and NRBAF before and after the fire. \[\text{NBR}=(\rho_{\text{NIR}}-\rho_{\text{MIR}})/(\rho_{\text{NIR}}+\rho_{ \text{MIR}}) \tag{2}\]  
\[\text{dNBR}=\text{NBR}_{\text{BF}}-\text{NBR}_{\text{AF}} \tag{3}\]  
The severity of the fire was then classified from an adaptation of the study of [PERSON] and [PERSON] (Table 6) (2017). Carbon sequestration was quantified on the basis of the CO2 flux index (Equation (4)) ([PERSON] and [PERSON], 1991), where sPRI is the photochemical reflectance index (PRI) ([PERSON] and [PERSON], 1991), reclassified from 0 to 1 (Equation (5)). \[\text{CO}_{2}\text{flux}=\text{NDVI}\times\text{sPRI} \tag{4}\]  
\[\text{sPRI}=(\text{PRI}+1)/2 \tag{5}\]  
PRI shows the relationship between the blue (\(\rho_{\text{Blue}}\)) and green (\(\rho_{\text{Green}}\)) bands (Equation (6)). PRI allows for establishing the relationship between photosynthesis and the efficient use of radiation. Therefore, it is a good indicator of the photosynthetic function of plants, at both the leaf- and the canopy-level scales ([PERSON] and [PERSON], 1991). \[\text{PRI}=(\rho_{\text{Blue}}-\rho_{\text{Green}})/(\rho_{\text{Blue}}+\rho_{ \text{Green}}) \tag{6}\]  
The CO2 flux index was validated on the basis of the obtained GPP from one of the products of Terra/MODIS (MOD17A2H) ([PERSON] and [PERSON], 1991). This product is available with data aggregated over 8 days, a spatial resolution of 500 m, and a scale factor of 0.0001. GPP is based on the concept of efficiency of solar radiation used by vegetation, and the daily GPP can be obtained through Equation (7). IPAR is the active photosynthetic radiation incident on the surface of the vegetation (MJ/m\({}^{2}\)). FPAR is the fraction absorbed by the vegetation (dimensionless). \(\varepsilon\) is the light-use efficiency of the vegetation (gC/MJ).