# Effects of Precipitation and Fire on Land Surface Phenology in the Brazilian Savannas (Cerrado)
###### Abstract
In addition to precipitation, disturbances such as fire, both natural and human-induced events, change the vegetation physiognomy and structure, influencing species abundance and diversity [10; 11; 12; 13]. Projected climate change scenarios indicate a likely increase in fire frequency and a reduction in plant growth, driven by warmer and especially drier conditions [14]. In the Brazilian savannas, this is expected to result in shorter fire-free periods affecting the development of grasslands and woodlands. The problem is exacerbated by the use of fire as a management tool in agricultural practices, especially in the northern portion of the Cerrado biome, which serves as a major ignition source for wildfires spreading into surrounding native vegetation. The increasing human occupation and the modification in the natural fire regime have contributed to Cerrado accounting for approximately 70% of Brazil's burned areas [15]. Fire affects foliage cover and introduces variability in the phenological metrics of the different vegetation physiognomes. It has immediate effects on both vegetative and reproductive phenophases, affecting the number of flowers and fruits of woody species, and enhancing vegetative propagation of herbs and shrubs [16]. However, as reported by [PERSON] et al. [16], the long-term persistence of fire effects and their influence on the timing of vegetative phenological events in the savanna physiognomies of the Brazilian Cerrado remain unclear. Although these events are common throughout the biome and frequent during the local dry season (June to September), the impact of this disturbance on the determination of phenological metrics, such as Amplitude (AMP), Start (SOS), and End (EOS) of the growing season, and seasonal integrals, remains largely unexplored in the Brazilian savannas. Understanding how vegetation phenology varies in response to changes in precipitation, as well as the effects of fire and post-fire savanna regrowth in affected areas, is crucial for conservation planning and monitoring [17; 18]. Thus, given that changes in environmental conditions can influence vegetation responses [19; 20; 21], this research is important for understanding phenological variations under climate change and, consequently, for supporting strategies to conserve the biome [22]. In savanna-protected areas in Brazil, studies of Land Surface Phenology (LSP), which derive vegetation phenological metrics from satellite observations, are the only viable option for conducting large-scale investigations. These studies can complement field phenological observations, which typically focus on individual species [23; 24]. However, research analyzing the LSP of native vegetation from the Cerrado biome remains limited,hindering our understanding of the relationships between precipitation, fire, and various phenological metrics that describe vegetation dynamics across different seasonal cycles. From the set of available orbital instruments, the Moderate Resolution Imaging Spectro-radiometer (MODIS) offers valuable opportunities for monitoring vegetation changes in shrubland and grassland ecosystems [25]. However, one reason for the scarcity of LSP studies using MODIS in the Cerrado is the small size of some protected areas, including ecological stations, parks, or conservation units. With a few exceptions, most of these preserved areas are inadequately viewed at the 250-m spatial resolution of MODIS. However, for large protected areas such as the EMAS National Park (ENP), observations from the MODIS MOD13Q1 product provide over 20 years of temporal coverage at 16-day composite intervals and 250-m spatial resolution [26]. In principle, this product enables long-term analysis of the NDVI response of Brazilian savannas to changes in precipitation across dry and wet seasonal cycles, as captured through long-term rainfall data from meteorological stations.