# Effects of Precipitation and Fire on Land Surface Phenology in the Brazilian Savannas (Cerrado)
## 4 MODIS LSP metrics
### Pre- and Post-Fire Behavior of NDVI-Derived LSP Metrics from the MOD13Q1 and HLS Products
Figure 13: Seasonal variations in HLS-derived NDVI, highlighting the effects of 2021 fire event and resultant burned area on NDVI response of savanna grasslands. In comparison with the control site, this event is marked by a decrease in the NDVI (dashed circle in red) during the dry season (symbols in orange at the top of figure) of the 2020/2021 cycle, and by a notable post-burning vegetation recovery at the start of the subsequent rainy season (symbols in green at the top of figure) from the following 2021/2022 cycle. The dashed square indicates the intersection point of the NDVI response for burned and non-burned grassland sites. To ensure confidence in the data analysis, we plotted the relative frequency distribution of the 500 pixels sampled from both control and burned sites for the NDVI-derived HLS metrics SSI, BL, and VES. Results are shown across the seasonal cycles before the fire (2019/2020), during the fire event (2020/2021), and after the fire (2021/2022 and 2022/2023 cycles) (Figure 15). Confirming the previous MODIS results from Figures 11 and 12, the SSI in burned areas (represented by red histograms in Figure 15) increased compared to control sites (green histograms) in the 2020/2021 and 2021/2022 cycles, while the opposite trend was observed for BL and VES. For each metric, the differences between control and burned sites were small in the pre-fire cycle, as expected, increased during the 2020/2021 (fire occurrence) and 2021/2022 (vegetation recovery) cycles, and decreased again in the 2022/2023 cycle. Metrics like VES exhibited also changes in data variability, as reflected in the altered shape of the histograms (Figure 15). Finally, confirming the Hedge's G pattern observed for VSS in Figure 14, the spatial distribution of this metric was altered in the fire-affected site compared to the control site (Figure 16). Consistent with our previous results, the most significant changes in VSS occurred during the 2021/2022 cycle, following the major fire event in 2021, as indicated by the shift from green to orange and red colors in the burned area (Figure 16). For the VES (Figure A4 in Appendix A), the most significant effects of the disturbance were observed during the 2020/2021 cycle, aligning with the results (red line) presented in Figure 14. However, a detailed examination of the VES image in Figure A4 revealed residual fire effects in the 2021/2022 cycle for certain pixels within the burned area, though these effects were not substantial enough to impact the Hedge's G metric. Figure 14: Effect size of fire occurrence starting on 10 July 2021, on HLS-derived Land Surface Phenology (LSP) metrics, calculated from NDVI, for seasonal cycles ranging from 2019/2020 (pre-fire) to 2022/2023. The Hedge’s G metric was used to compare adjacent burned and non-burned (control) grassland areas. The burned area influenced the determination of LSP metrics beyond the shaded area, affecting both the seasonal cycle during which the event occurred (2020/2021) and the following cycle (2021/2022). Abbreviations are defined in the text. Figure 16: Spatial variation in the Value for the Start of Season (VSS) across control and burned sites, highlighting the effects on the subsequent seasonal cycle following the fire event on 10 July 2021. Results are presented for the seasonal cycle preceding the fire event (2019/2021), the cycle during which the fire occurred (2020/2021), and two post-fire cycles characterized by vegetation recovery (2021/2022 and 2022/2023). Figure 15: Pairs of Gaussian-fitted histograms for the control (Site 1) and burned (Site 2) grassland sites, illustrating relative variations in the HLS-derived phenological metrics: Small Seasonal Integral (SSI; **top**), Base Level (BL; **middle**), and Value for the End of the Season (VES; **bottom**). Results are presented for the seasonal cycle preceding the fire event (2019/2021), the cycle during which the fire occurred (2020/2021), and two post-fire cycles characterized by vegetation recovery (2021/2022 and 2022/2023).