Long-term post-fire dynamics of alternative vegetation states in a seasonally dry subtropical forest

GIORGIS, MELISA A.; ZEBALLOS, SEBASTIÁN R.; JAUREGUIBERRY, PEDRO; LIPOMA, LUCRECIA; CINGOLANI, ANA M

Madrid

Simposio; 64th Annual Symposium of the International Association for Vegetation Science; 2022

IAVS

Background Fire is a key factor in maintaining alternative biome states in tropical and subtropical seasonal climates, potentially covered by forest. Several studies have explored the short-term dynamics of contrasting vegetation physiognomies following fire; while very few have tracked such responses in the longer term. Our aim was to evaluate how floristic composition and physiognomy vary over time in treeless physiognomies and forest patches with different fire histories in a subtropical dry forest. Material and methods In 2008 we selected 35 plots in forests, shrublands, and grasslands, resulting from different fire histories and other environmental factors. In September 2011 a fire burned 16 plots, including one forest and several shrublands and grasslands. Floristic and physiognomic surveys were performed at the end of each growing season in 2008, five months after the 2011 fire, and subsequently every two years until 2020. Results Burned shrublands recovered the pre-fire floristic composition after three growing seasons and their physiognomy after five seasons. Burned grasslands recovered their pre-fire floristic composition after five growing seasons and their physiognomy after only one season. The burned forest plot was transformed into a shrubland, and remained as such over time. Floristic composition and physiognomies of plots that did not burn in 2011 changed over time, but the changes were always less pronounced than in the burned sites. Conclusions Our 12-year tracking study shows that fire can have long-lasting effects on forest patches, transforming them into shrublands. Burned grasslands and shrublands can return to the pre-fire state in a short time, differing in the recovery times for floristic composition and physiognomy. Our results have important implications for fire management and the conservation of the different physiognomies in the region, where highly fragmented forest patches only account for 5% of the landscape cover, compared to 30 % for shrublands