Fire has played an important role in the plant dynamics and diversity of the Cerrado for millions of years. We evaluated fire behaviour in different fire seasons in areas of an open savanna, providing information for fire management plans. It has been hypothesised that early fires (May – end of the rainy season) will be less intense than those conducted in the middle and end of the dry season (July and October) owing to the amount of dead biomass accumulated. Therefore, we compared fire behaviour in early, mid- and late dry season, evaluating the main fire and environmental variables. Fire intensity was mainly influenced by the combination of dead fuel percentage and fuel load. Even though this combination was the best model to explain fire intensity variability, fire parameters (including fire intensity) did not differ between fire seasons. Flame height was best explained by dead fuel percentage + fuel moisture content, dead fuel percentage + fuel load and also by dead fuel percentage. Our study showed that, in areas with fire exclusion for 2 years, fire season did not influence fire parameters and fire behaviour and the main factors influencing fire intensity were the proportion of dead biomass and total fuel load.

Some invasive grasses have been reported to change fire behavior in invaded plant communities. Urochloa brizantha is an aggressive invasive grass in the Brazilian Cerrado, an ecosystem where fire is a common disturbance. We investigated the effects of U. brizantha on fire behavior in an open Cerrado physiognomy in Central Brazil. Using experimental burnings we compared fire behavior at both the community and the individual plant level in invaded (UJ) and non-invaded (NJ) areas burned in July. We also assessed the effect of fire season in invaded areas by comparing July (UJ) and October (UO) burnings. We evaluated the following variables: fuel load, fuel moisture, combustion efficiency, maximum fire temperature, flame height, and fire intensity. Additionally, we evaluated the temperatures reached under invasive and native grass tussocks in both seasons. Fuel load, combustion efficiency, and fire intensity were higher in NJ than in UJ, whilst flame height showed the opposite trend. Fuel amount and fire intensity were higher in October than in July. At the individual plant level, U. brizantha moisture was higher than that of native species, however, temperatures reaching C600°C at ground level were more frequent under U. brizantha tussocks than under native grasses. At the community level, the invasive grass modified fire behavior towards lower intensity, lower burning efficiency, and higher flame height. These results provide essential information for the planning of prescribed burnings in invaded Cerrado areas.

This work was accomplished in a trail located inside a legal reserve in the Campus of UNESP (Universidade Estadual Paulista) in Bauru, characterized especially by the "cerrado" vegetation (savanna). The area has been used for practical field activities of the project "Wandering and Learning in the cerrado" in which students are guided into a practical class about Ecology and Botany. The family Vochysiaceae was chosen for having the greatest representativeness in this environment, besides it holds species with typical morphology from cerrado species: twisted and corky stems and some species with leathery leaves. It also allows the illustration of various ecological interactions through live examples during the field practice class. The identified species were: Qualea cordata Spreng., Qualea grandiflora Mart., Qualea multiflora Mart., Qualea parviflora Mart., Vochysia cinnamomea Pohl and Vochysia tucanorum Mart. Such species were described and samples herborized. Information about ethnobotanical and ecological interactions were searched in the literature and observed in the field. With these data it was elaborated a species catalog, an identification key and a glossary. Such tools are intended to support the practical activity of the teacher in the practical activity and to promote motivation and interest among the students. Resumo: Este trabalho foi realizado em uma trilha localizada na Reserva Legal do Campus de Bauru da UNESP, caracterizada especialmente por vegetação de cerrado. Este espaço é utilizado para o desenvolvimento de atividades práticas de campo de um projeto denominado "Passeando e aprendendo no cerrado", no qual alunos dos três níveis de escolaridade são guiados para uma aula prática de Ecologia e Botânica. A família Vochysiaceae foi escolhida como objeto da proposta por ter grande representatividade neste ambiente e possuir elementos com morfologia típica das espécies de cerrado: caules tortuosos, suberosos e algumas espécies com folhas coriáceas. O grupo possibilita ainda a visualização de diversas interações ecológicas durante aula prática de campo. As espécies identificadas foram: Qualea cordata Spreng., Qualea grandiflora Mart., Qualea multiflora Mart., Qualea parviflora Mart., Vochysia cinnamomea Pohl e Vochysia tucanorum Mart. Tais espécies foram descritas, herborizadas e fotografadas. As informações sobre etnobotânica e interações ecológicas foram buscadas na literatura e observadas em campo. A partir destes dados, foram elaborados: um catálogo de espécies, uma chave de identificação e um glossário. Tais ferramentas propõem auxiliar a atividade prática do docente e tornar o estudo destes tópicos mais motivadores e interessantes aos alunos. Palavras-chaves: biodiversidade, ensino de botânica, aula prática de campo, cerrado.

Fire is a main disturbance structuring vegetation worldwide, but few studies have addressed differences in time since last fire and its relationship to fuel load characteristics and fire behavior in Neotropical savannas. We aimed to investigate fire behavior in a Cerrado open savanna of Central Brazil by conducting prescribed fires in areas with different fire-free intervals: one year (FI-1), two years (FI-2), and four years (FI-4). Specifically, we evaluated (1) the amount of live, dead, and total biomass (components of the fuel load); (2) fire behavior, including fire temperatures in three different heights (1 cm belowground, on the soil surface, and 50 cm aboveground), fire duration, residence time, fire intensity, rate of spread, and flame height; and (3) the relationship between soil heating, fuels, and fire by identifying the most important parameters driving soil heating. Total and dead fuel loads were greater in areas with longer fire-free intervals in comparison with areas burned the previous year, with the greatest increment to the fuel bed occurring in the first two years after fire. Greater fuel loads (consequently greater dead fuel loads) resulted in differences in belowground soil heating (-1 cm), where temperatures varied from 39 to 82°C in FI-2 plots and from 40 to 131°C in FI-4 plots; in FI-1 plots temperatures belowground varied from 29 to 68°C. Temperatures on the soil surface and 50 cm aboveground were also greater in plots with longer fire-free intervals, reaching over 400°C on the soil surface and exceeding 500°C 50 cm aboveground. Finally, amount of dead fuel was the best predictor of belowground soil heating, highlighting the importance of fuel loads, which is a key factor to be monitored in fire management plans of Cerrado open savannas.