Isolated Trees in a Fragmented Tropical Landscape: A View Through the Soil Seed Bank

Abstract

Tropical soil seed banks under isolated trees in pastures remain relatively understudied despite their important role in forest regeneration. Here, we investigated patterns of plant species diversity, abundance, and composition in the soil seed banks of cattle pastures, under fleshy-fruited, and nonfleshy-fruited trees within pastures, and in secondary forest patches at ten study sites in Brazil. We also examined how the fruit traits of isolated trees affected seed bank communities, predicting that fleshy-fruited trees are more connected to frugivory and seed dispersal networks than trees without fruit resources, and would therefore have richer seed banks. We found that the species richness and diversity of seed bank communities were higher in secondary forest patches and under fleshy and nonfleshy-fruited trees compared to soil samples from open pastures, although early successional plants were dominant across all habitats. The fruit traits of isolated trees also affected the richness of seeds dispersed by animals and abiotically. Seed banks under fleshy-fruited trees had more seeds of bird-dispersed plants compared to nonfleshy-fruited trees. Overall, our results show that soil seed banks under isolated trees are more similar to those in secondary forest patch seed banks, especially trees bearing attractive fruit resources that likely increase connectivity to frugivory and seed dispersal networks active in fragmented landscapes.