Flowering phenology and its implications for management of big-leaf mahogany Swietenia macrophylla in Brazilian Amazonia

Abstract

Premise of the study: Flowering phenology is a crucial determinant of reproductive success and offspring genetic diversity in plants. We measure the fl owering phenology of big-leaf mahogany ( Swietenia macrophylla , Meliaceae), a widely distributed neotropical tree, and explore how disturbance from logging impacts its reproductive biology. • Methods: We use a crown scoring system to estimate the timing and duration of population-level fl owering at three forest sites in the Brazilian Amazon over a fi ve-year period. We combine this information with data on population structure and spatial distribution to consider the implications of logging for population fl owering patterns and reproductive success. • Key results: Mahogany trees as small as 14 cm diam fl owered, but only trees > 30 cm diam fl owered annually or supra-annually. Mean observed fl owering periods by focal trees ranged from 18–34 d, and trees fl owered sequentially during 3–4 mo beginning in the dry season. Focal trees demonstrated signifi cant interannual correlation in fl owering order. Estimated population-level fl owering schedules resembled that of the focal trees, with temporal isolation between early and late fl owering trees. At the principal study site, conventional logging practices eliminated 87% of mahogany trees > 30 cm diam and an estimated 94% of annual pre-logging fl oral effort. • Conclusions: Consistent interannual patterns of sequential fl owering among trees create incompletely isolated subpopulations, constraining pollen fl ow. After harvests, surviving subcommercial trees will have fewer, more distant, and smaller potential partners, with probable consequences for post-logging regeneration. These results have important implications for the sustainability of harvesting systems for tropical timber species.

Citation

Grogan, J.; Loveless, M. D. 2013. Flowering phenology and its implications for management of big-leaf mahogany Swietenia macrophylla in Brazilian Amazonia. American Journal of Botany. 100(11): 2293-2305.