O efeito do fogo sobre a inflamabilidade e a estabilidade de florestas estacionais deciduais do Parque Estadual do Pau Furado – MG

Abstract

Fire plays a crucial role in maintaining and balancing diverse ecosystems. In some, it is natural, while in others it represents a disturbance. In the Cerrado, savannas predominate, but patches of seasonal forests create mosaics. Inadequate management and land use practices have altered fire regimes, resulting in frequent fires in forests. These disturbances can modify vegetation and fire patterns, leading to a transition called “savannization”. This process involves opening the canopy after a fire, favoring the invasion of grasses and increasing flammability, making it difficult for trees to recover canopy. The objective of the present study was to investigate how the occurrence of frequent fires affects the flammability of seasonal forests and whether this process depends on the number of fires, the soil and anthropogenic influence. We also seek to analyze whether this process is reversible and estimate the time needed to recover the low flammability characteristic of forests. The study was carried out in the Pau Furado State Park – MG where collections were made in 31 plots distributed in 3 different classes: plots that burned once, twice or were never burned. Measurements were taken and samples were collected to determine values related to flammability such as fuel height layer, graminoid and non-graminoid biomass, branches of different thicknesses, litterbed and soil vegetation cover. Soil samples were also collected for physical analysis, and geographic coordinates were recorded to obtain data on fire history and proximity to pastures. To test whether fuel parameters were related to fire history and soil variables, we fit generalized linear models (GLM) with fuel parameters as response variables and fire and soil variables as predictors. The factors that best explained the variation in flammability were the time since the last fire and the proximity to pastures for grass biomass, the sum of bases for thin branches and the number of fires for thick branches. The increase in grass biomass in the investigated plots highlights that the influence of land use near the burned areas is the key factor in the transition of phytophysiognomy. The increase in the biomass of thin and thick branches changes the characteristics of the fire, making it more intense and lasting, reducing the resilience of the forests and accelerating the “savannization” process. Recognizing how the passage of fire and changes in its regimes can facilitate ecosystem transition in Cerrado mosaic formations is crucial for adequate management of land use and for the conservation and sustainability of ecosystems, particularly in Conservation Units.