Seed germination of herbaceous and woody species of the Sudanian savanna-woodland in response to heat shock and smoke

Fire-related cues (smoke and heat) contribute largely to changes in vegetation communities in fire prone habitats. The germination responses of seeds of species from Combretaceae, Leguminosae and Poaceae to smoke, heat or their interaction were examined. Half of the seed batch was first exposed to cold aerosol smoke for 60 min. Untreated and smoked seed batches were then subjected to heat treatment by incubating them at 40 °C, 80 °C or 120 °C for 2.5 min. The results showed that the seed germination of fire-adapted species, Terminalia avicennioides (p < 0.01) and Pteleopsis suberosa (p < 0.05), was stimulated by smoke, while the germination of fire-sensitive species, Anogeissus leiocarpus (p < 0.001) and Andropogon gayanus (p < 0.05) was inhibited by heat and smoke, respectively. Seeds of fire-tolerant species (Combretum glutinosum and Combretum nigricans) germinated favorably in response to heat and smoke treatments. The germination response of leguminous species was not significant with respect to the smoke and heat levels applied. In conclusion, there was no persistent pattern across all species that can easily explain their responses to fire-related cues, which can be related to species-specific requirements for a given dosage–response level, which in turn is attributed to the levels of heat shock and smoke treatments adopted in the present study. Testing different exposure times to heat shock and varying doses of smoke on large number of species is needed before generalization about community level response to fire could be drawn.