SEED SIZE OF WOODY-PLANTS IN RELATION TO DISTURBANCE, DISPERSAL, SOILTYPE IN WET NEOTROPICAL FORESTS

Fresh and dry masses of seeds of woody species collected at Mabura Hil l, Guyana were evaluated according to dispersal mode, gap size prefere nce, and soil type. Data published for woody species from Manu, Peru a nd Barro Colorado Island (BCI), Panama were analyzed by dispersal mode and gap size preference for comparison. Larger seeds at the three sit es were significantly associated with canopy or emergent trees or lian as that are dispersed by mammals or gravity and recruit best in small gaps. Variation in seed size, after accounting for the effects of plan t height and life-form, could be explained by dispersal mode (Mabura H ill: 22%, Manu: 14%, BCI: 26%) and gap size preference (Mabura Hill: 9 %, Manu: 7%, BCI: 11%). Soil type preference, analyzed only for Mabura Hill, was not associated with seed size. Mean seed size at Mabura Hil l was significantly larger than at Manu or BCI. Short-term successiona l processes may explain the variation of seed size within sites; dispe rsal mode is particularly important in defining seed size selection du ring a the successional process. However, short-term successional proc esses cannot explain the variation of seed size among sites. It is sug gested that this variation may be attributed to differences in the eff ects of larger-scale variations in soils and disturbance on seed size among the three sites.