Do savanna trees mast? Phenological dynamics of flowering and fruiting in savanna tree species.

Abstract

A priori, it is not clear if masting should be expected in savannas and few studies have attempted to detect masting in savannas. We tracked the flower and fruiting phenology of 18 savanna woody species on a monthly basis in Kruger National Park for 8 years. We used multiple metrics to detect masting including phenological intensity and its CV, phenological volatility, synchrony and the proportion of failure years. Additionally, we used a process-based model of plant growth to test whether resource matching could explain the observed phenological behaviour. Overall, the measured masting metrics provided no unequivocal evidence for masting. For 4 of the 18 study species, the fruiting CV, synchrony and volatility were consistent with masting. The process-based model of plant growth could reproduce observed flowering and fruiting behaviour, suggesting that resource matching could explain the observed phenological behaviour of the species. We propose that future research should explore the possibility that masting may not be selected for in savannas due to the prevalence of generalist pollinators, dispersal agents and seed predators. Although masting does not appear to be a prevalent phenological strategy in savannas, we detected large between species variation in reproductive phenology, which is likely to have consequences for the trophic dynamics of the study system.