Soil seed bank, seed removal, and germination in a seasonally dry tropical forest in Veracruz, Mexico

Abstract

The soil seed bank has a limited role in the seasonal dry tropical forest regeneration process, but seed removal and germination can also be limiting factors during the early forest recovery. In central Veracruz, Mexico, the soil seed bank was determined en five fallows and two forests. Seed bank decreased from fallow to forest (1303 to 101 seeds m-2); herbs and grasses predominated thus the similarity between species composition of seed bank and vegetation was low. Seed removal and germination were evaluated for Acacia cochliacantha, Caesalpinia cacalaco, Ipomoea wolcottiana and Senna atomaria in contrasting habitats represented by pasture, fallow and forest. Seed removal was determined under treatments of total access, rodent exclosure, and insect exclosure. Caesalpinia (largest seeds) displayed the lowest seed removal (5%), whereas Senna (63%) and Ipomoea (29%) displayed the highest. Rodent exclosure reduced seed removal for Ipomoea (medium-sized seeds); and insect exclosure reduced removal for Senna and Acacia (small seeds). With the exception of Senna (18% germination), the scarified seeds displayed the highest germination percentage (53-99%). For all species, germination was higher in forest than in open habitats, only Senna seeds displayed the lowest germination percentage in the forest habitat. Results suggested that in the dry forest of Veracruz, seed removal may not limit forest regeneration; however seeds must be scarified for use in restoration activities.