Seasonal rhythms and phenological plasticity of savanna woody species in a fallow farming system (south-west Burkina Faso)

Leafing, flowering and fruiting of the 24 most representative species of trees and shrubs in Sudanian savannas and fallows near Bondoukuy (Burkina Faso) were studied for 2 y (May 1992 toJune 1994). The period of defoliation was generally brief, and leaf flushing, flowering and fruiting occurred mostly in the dry season. The phenological behaviour varied nonetheless across species and indi- viduals. A classification taking into account synchrony/asynchrony and duration in foliation, flowering, fruit ripening and seed dispersal phases allowed comparison of species' phenological plasticity. Species were distributed along a scale of increasing plasticity, from trees to shrubs. Along this scale, species of the Leguminosae appeared to be separated from those of the Combretaceae, the latter being gener- ally considered as characterising fallow farming systems. These results provide new evidence about the effect of phylogenetic constraints on the phenological behaviour of the woody species of the Sudanian savannas.

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