Effects of post-fire on seed germination and seedling recruitment of a generalist savanna woody species.

Temperature and humidity are key factors influencing seed germination, varying across vegetation types and in response to disturbances such as fire. This study investigated germination, recruitment, and seedling growth of the generalist tree Vochysia tucanorum Mart. (Vochysiaceae) in natural environments of southern Brazil, including savanna, savanna - forest transition, and forest vegetation. Three months after a fire event, we established 12 nurseries for treatment (four per vegetation type, each containing 15 seeds) and monitored environmental conditions and seedling development from December 2022 to July 2023. Data on temperature, humidity, germination, mortality, seedling height, and cotyledon thickness were compared between burn and unburn treatments. Average temperature differed among vegetation types but not between burned and unburned areas, while humidity increased by 28% in burned plots. The number of seeds that germinated was significantly higher in burned areas across all vegetation types. Seedlings in the savanna were smaller (mean 16 mm) than those in the transition (29.6 mm) and forest sites. Cotyledon thickness varied over time and between treatments but was not affected by vegetation type. Despite the wide ecological distribution of V. tucanorum, germination and recruitment were rare events. The limited germination in savanna vegetation indicates that microclimatic constraints, particularly reduced water availability, restrict seedling establishment. Once germinated, seedling growth depends largely on cotyledon reserves, which deplete more slowly in burned environments. These results improve our understanding of post-fire regeneration in a generalist wood species and demonstrate how fire and microclimatic conditions jointly influence recruitment dynamics in fire-prone environments.