Reproductive phenology of woody species in a north Australian tropical savanna

Interspecific and interannual variation in reproductive phenology was quant ified for 50 common species of trees and shrubs from a mesic savanna near D arwin, northern Australia. The presence of buds, Bowers, and fruit was note d over a 30-month period, from September 1992 to February 1995. Surveys wer e undertaken at: monthly intervals for the less common species, and at bimo nthly intervals for ten of the common trees and tall shrubs. The majority o f species flowered each year at about the same time. There was no evidence of sub-annual or continuous regimes of reproductive phenology. There was no supra-annual carryover of seed-bearing fruit in the canopy of any species. The peak flowering periods were the mid to late dry season (July-August) a nd the transition between the dry season and the wet season (October-Novemb er). The two dominant trees--Eucalyptus miniata and E. tetrodonta--flowered during the dry season, thereby providing resources for some elements of th e vertebrate Fauna. Flowering and fruiting were uncommon at the end of the wet season (February/March), although two species that flower and fruit ar this time (E. porrecta and Terminalia ferdinandiana) may provide resources to consumers at a time when floral or fruit resources are otherwise scarce. Because the peak of reproductive activity takes place during the late dry season, fruit maturity and seed dispersal have occurred prior to the onset of the rainy season for most species, and germination and seedling establis hment potentially may take effect in response to the first rains. Late dry season fires, which tend to be extensive and incense, are a potential threa t to the floral and fruit reserves within these savannas.