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

Fresh and dry masses of seeds of woody species collected at Mabura Hill, Guyana were evaluated according to dispersal mode, gap size preference, and soil type. Data published for woody species from Manu, Peru and Barro Colorado Island (BCI), Panama were analyzed by dispersal mode and gap size preference for comparison. Larger seeds at the three sites were significantly associated with canopy or emergent trees or lianas that are dispersed by mammals or gravity and recruit best in small gaps. Variation in seed size, after accounting for the effects of plant height and life-form, could be explained by dispersal mode (Mabura Hill: 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 Hill was significantly larger than at Manu or BCI. Short-term successional processes may explain the variation of seed size within sites; dispersal mode is particularly important in defining seed size selection during a the successional process. However, short-term successional processes cannot explain the variation of seed size among sites. It is suggested that this variation may be attributed to differences in the effects of larger-scale variations in soils and disturbance on seed size among the three sites.