Effects of prescribed burning on fire regime dynamics in Amazonian savanna ecosystems

Prescribed burning has been adopted as a strategic tool within Integrated Fire Management (IFM) of pyrophytic ecosystems, and there is a growing need to provide evidence supporting its effectiveness in reducing wildfire occurrence. As the first study to systematically quantify the contributions of prescribed burning in Amazonian savanna ecosystems, it evaluates its effects on fire dynamics in the largest savanna enclave in the southern Brazilian Amazon, with emphasis on fire seasonality, fire size, and the extent of fire-affected sensitive vegetation. A fire-scar database was compiled using semi-automated classification procedures applied to Landsat imagery, and records were classified by fire type, seasonality, and size classes. The analysis was segmented into three periods that coincide with abrupt changes in the territorial fire management of the area: T1 (1998-2006), before establishment of Campos Amazônicos National Park; T2 (2007-2015), fire-exclusion policy; T3 (2016-2024), IFM with prescribed burns. Analysis of variance was used to determine whether statistically significant differences occurred among dependent variables derived from fire dynamics patterns across the study periods. Over the past 27 years, a total of 16,589 km² of burned area was detected, distributed across 2962 fires. The average percentage of sensitive vegetation burned in wildfires was 3.3 times higher than in prescribed burns (5.2 ± 13.4% for wildfires, compared with 1.6 ± 2.9% for prescribed burns). The use of prescribed burning in T3 was associated with a 31.4% reduction in the percentage prevalence of burned areas in the late dry season compared to T2 (F = 7.297; p = 0.00335), along with a 29.2% reduction in the annual proportion of fire-affected sensitive vegetation. The findings underscore the effectiveness of prescribed burning as a tool for reducing late dry season burned-area prevalence and protecting sensitive vegetation. Prescribed burning should be incorporated into IFM strategies in Amazonian open ecosystems to manage accumulated and continuous fuel in savanna and grassland environments and enhance ecosystem resilience under current and future climate conditions.