# Effects of Precipitation and Fire on Land Surface Phenology in the Brazilian Savannas (Cerrado)
## 4 Discussion  
Our study contributes to the understanding of vegetation phenology in the Brazilian savannas (Cerrado) in several ways. It provides insights into fire-related variability for further long-term trend analyses of satellite-based indicators of vegetation phenology. We found that certain metrics increased in response to both precipitation and fire, with the effects of fire generally being more pronounced than those of precipitation. Given that LSP metrics are often used as input data for classifying savanna vegetation, our findings suggest also that the selection of seasonal cycles influenced by droughts, and consequently by rising fire frequency, can introduce significant variability into the classification results. Our work contributes also to future research employing diverse or more in-depth approaches to better understand savanna dynamics in the face of climate change and fire disturbance. This knowledge is important for developing appropriate conservation strategies in the Brazilian savanna areas. In the Cerrado, fire is an important ecological element in maintaining its vegetation. However, fire frequency and intensity have been increasing due to climate change, land-use and land-cover changes, and overall human occupation, particularly in the new agricultural frontiers of the Brazilian savannas (e.g., MATOPIBA region) [14; 15]. Consequently, there is a reduction of the biome's regeneration capacity, causing loss of woody species. Under predicted scenarios of warmer and drier conditions, the occurrence of fire is expected to spread, making the monitoring of vegetation phenology with satellites essential. Land-degraded areas are projected to increase in the near future, and the recovery of savanna vegetation will vary among woody species. In our study, fire and vegetation recovery in burned areas introduced data variability into LSP metrics, likely influencing the correlations between phenological metrics and precipitation. The effects were observed during both the cycle in which the disturbance occurred and the post-fire cycle. In this context, the study of the relationships between vegetation phenology and precipitation is important for understanding vegetation productivity, carbon storage, and carbon cycle in terrestrial ecosystems [44]. Distinct responses of savannas to rainfall variability may be also influenced by the ratio of woody to herbaceous biomass. In general, higher woody biomass fractions promote greater stability and resilience to potential scenarios of climate change [50]. In the Brazilian savanna, precipitation and the resultant soil moisture availability are the primary drivers of vegetation structure and diversity [51]. Precipitation, soil moisture conditions, and the availability of dry biomass (fire fuel) are also key factors controlling fire occurrence in the Cerrado biome [11; 52]. Our results confirmed that the interannual variations in rainfall had distinct effects on the determination of phenological metrics in grassland and woodland areas of the ENP over the studied seasonal cycles. In grassland areas, MODIS NDVI-derived LSI and SSI were the most sensitive LSP metrics to rainfall during vegetation growing cycles, as evidenced by the positive correlations between accumulated precipitation in the rainy season and these TIMESAT metrics. In woodland areas, AMP, EOS, LSI, RIBS, and SSI also increased in response to seasonal cycles of higher precipitation. Therefore, seasonal cycles of higher precipitation extended the local growing season, increasing vegetation greenness at the start of the season, and enhancing overall NDVI variability and vegetation activity throughout the growing period, as indicated by the behavior of these LSP metrics with increased precipitation. In the literature, these metrics are also important for monitoring other ecosystems. For example, EOS is valuable for evaluating vegetation dynamics in response to severe droughts, while AMP reflects the intensity of vegetation seasonality and its resilience to extreme climatic events.