Seed rain in an econtonal region between Cerrado and Caatinga in Piauí, Brazil

Abstract

Studies on seed rain can provide useful information on the spatial distribution, density, and richness of species. This study aimed to sample the seed rain in “capões” with the presence and absence of Copernicia prunifera (Carnaúba), characterizing the seeds as for their dispersion syndrome and life forms, and explore the relationship between the monthly rainfall totals and the density and number of species in the seed rain and the seasonality in seed deposition. The research was conducted in 20 capões, (10 with the presence and 10 with the absence of Copernicia prunifera). Three collectors of 0.50 m2 were placed in each capão. A total of 1,666 diaspores (55.5 seeds/m2), belonging to 17 families and 32 species, were collected. There was a negative relationship between rainfall and the number of seeds (r =-0.73 and p<0.05) and between rainfall and number of species in the seed rain (r =-0.78 and p<0.01). There was an increase in the number of species in the seed rain with an increase in the number of seeds (r = 0.74 and p<0.001). Twelve zoochoric, 12 anemochoric, and 7 autochoric species were recorded, which accounted for 908, 502, and 256 seeds, respectively. Trees had 895 seeds collected, distributed in 12 species, followed by shrubs (574 seeds and 10 species), lianas (133 seeds and 7 species), and palms (61 seeds and 2 species). Anemochoric and zoochoric dispersion syndromes predominated in the dry period, with a predominance of zoochory in all months. There was a difference in the species composition in the seed rain between the capões with the presence and with the absence of Copernicia prunifera. The distance between the capões did not influence the seed rain composition (Mantel r =-0.11 and p = 0.74). There was no relationship between areas of capões and the number of seeds in the seed rain (R2 = 0.013 and p = 0.95).