Seasonal Flowering and Fruiting Patterns in Tropical Semi-Arid Vegetation of Northeastern Venezuela

Abstract

Flowering and fruiting phenology were studied for thorn woodland (annual precipitation of 1179 mm) and thorn scrub (annual precipitation of 578 mm) stands in northeastern Venezuela. The global phenology of each vegetation type was assessed using multivariate techniques (ordination and chronological clustering). All species and their respective phenophases were analyzed simultaneously. The flowering of trees and tall shrubs occurred in both vegetation types at the end of the dry season and lasted throughout the entire rainy season. Short-duration rains late in the dry season may have triggered and synchronized flowering. Fruiting activities of trees and tall shrubs occurred in all months, whereas fruiting maturation was limited to the dry season and the beginning of the rainy season. The fluctuation in the abundance of fruits was related principally to the production of a large amount of dry, lightweight seeds during the dry season, whereas fleshy and dry, heavyweight fruits were more or less steadily produced throughout the year. This suggests an adaptation to favor wind dispersion of seeds during the dry season when the vegetation is leafless, as well as the maintenance of animal populations as dispersal agents throughout the year. Periods of similar phenological characteristics were statistically defined and compared to annual rainfall and soil moisture. Annual reproductive phenology was more synchronized for thorn scrub than for thorn woodland. This may be due to the fact that thorn scrub vegetation is subjected to more severe drought conditions and consequently responds more punctually to the reappearance of rain or soil moisture.