Resumen

FLORES, Saúl  y  DEZZEO, Nelda. Variaciones temporales en cantidad de semillas en el suelo y en lluvia de semillas en un gradiente bosque-sabana en la gran sabana, Venezuela. INCI [online]. 2005, vol.30, n.1, pp.39-43. ISSN 0378-1844.

Seasonal variation in the total soil seed quantity and in seed rain were studied along a forest-savanna gradient consisting of primary forest (1: mature forest), forest slightly affected by fire (2: secondary forest), forest strongly affected by fire (3: matorral), and open savanna (4), at the Gran Sabana, Venezuela. Seed soil quantity was determined by collecting 10 samples of the organic surface layer or of the first 10cm of mineral soil with a 20×20cm steel frame in both dry and wet seasons. Seed rain through the year was examined by collecting every two weeks the seeds that fell into 10 trays 90×40cm each. During the dry season the soil seed number was lower (P<0.05) in the savanna than in 1, 2 and 3. During the wet season it was higher (P<0.05) in the secondary forest than in the 1, 3 and 4. Seed rain in the primary forest was low and variable, with no well defined production peaks. In the secondary forest the seed rain was slightly higher than in the mature forest, showed a clear peak in October and no production between November and January. In the matorral the seed rain was high and showed well defined production peaks in March and May; this can be associated with the presence of pioneer species in this community. In the savanna the seed rain was slightly higher than in the 1 and 2, with a production peak in February. Spatial heterogeneity in the soil seed quantity and in seed rain was observed in all vegetation types, which may be associated with the distribution of species within each community, and with differences in the reproductive periods of these species. Disturbances seem to accelerate the seed production and the germination processes in the soils of the Gran Sabana.

Palabras clave : Gran Sabana; Lluvia de Semillas; Producción de Semillas; Semillas en el Suelo.