# Effects of Precipitation and Fire on Land Surface Phenology in the Brazilian Savannas (Cerrado)
## 4 Discussion
Persistent alterations in AMP may indicate areas undergoing ecological degradation that should be monitored [44]. When combined with SSI, which indicates vegetation vigor in the season, these metrics can help identify areas with potential for restoration or those requiring prioritization for conservation [45]. Monitoring these metrics in protected areas, such as the ENP, is crucial for guiding adaptive vegetation strategies, including controlled burns and firebreak maintenance. In the burned grassland site, vegetation recovery began a few days after the fire disturbance that occurred on 10 July 2021 during the local dry season of the 2020/2021 cycle. Vegetation recovery accelerated in October and November 2021 following the first rainfall events of the new seasonal cycle (October 2021 to September 2022), resulting in greener grasses (higher NDVI compared to the control site) from November through the end of the subsequent dry season, extending into September 2022. These results emphasize the superior adaptability of the Cerrado vegetation to fire events, particularly when compared to semi-arid ecosystems, where recovery may take up to two years after a fire due to severe drought conditions [13]. However, when compared to grasslands, the recovery of the structure and floristic composition of burned woody species may take up to eight years, as reported by [PERSON] et al. [56]. In the northern portion of the Cerrado biome, [PERSON] et al. [57] noted that areas with higher fire frequencies exhibited slower recovery rates of woody species, with significant effects on phenological metrics like the SOS and EOS. Our study has some limitations that should be addressed in future investigations. First, we used the MODIS MOD13Q1 vegetation index product, which is provided at 16-day intervals and a 250-m spatial resolution. While this product allows for consistent spatial and temporal comparisons of vegetation canopy greenness, an eight-day composite product would likely be a better alternative for LSP studies of savanna vegetation. However, due to the large field-of-view of MODIS, bidirectional and atmospheric effects resulting from view-illumination geometry during data acquisition could introduce additional uncertainties in the analysis. In reality, a comparison of MODIS-based LSP estimates in Canadian prairie grasslands has shown no significant difference in the phenological metrics derived from daily reference observations and multi-day NDVI resampled at a time step less than 18 days [58]. Second, another limitation is the current version of the TIMESAT software (version 3.3), which is not designed to handle irregular time series of vegetation indices like those produced by the HLS product, demanding data regularization steps. A new version of TIMESAT that can process irregular time-step data is expected to be released for the remote sensing community in the near future. In our study, we used interpolation and gap-filling techniques to overcome this limitation, converting the HLS product into a regularly spaced five-day product with near-nadir viewing. Third, it is important also to note that our analysis of the relationship between precipitation and LSP metrics did not detect severe dry or wet seasonal cycles during the selected period of MODIS observations (2002-2023) when compared to the long-term precipitation measured by the meteorological station (1983-2023). In addition to the influence of burned areas on the results, the absence of severe wet and dry seasonal cycles may have reduced data variability, potentially affecting the magnitude of the observed correlations between phenological metrics and precipitation, which were generally lower than 0.60. Finally, our approach, which primarily relies on statistical analyses, may not fully capture complex nonlinear relationships with LSP metrics. For instance, interrelated factors such as soil moisture, soil composition, and vegetation type, represented here by two broad classes (grasslands and woodlands), were not examined in detail.