Post-dispersal seed and seedling mortality of tropical dry forest trees after shifting agriculture, Chiapas, Mexico

Abstract

ABSTRACTVertebrate attack accounted for 98.4% of all seed loss during the two months following dispersal. This accounted for, across all habitat types, 94% ofBursera, 76% ofSpondias, 37% ofSwieteniaand 25% ofErythrinaseeds artificially dispersed.Bursera, SpondiasandSwieteniaseeds in early successional habitat suffered significantly greater predation than in either older abandoned (30 y) or mature forest plots.Erythrinashowed generally low loss to predation in all plots. Seeds attacked were more often removed from, rather than buried or eaten at, the dispersal site. In young secondary habitats, however, seeds ofBurseraandSpondiaswere more frequently eaten at the site. Seeds dispersed individually rather than in larger aggregations (5, 10) were more likely to survive in mature forest and late secondary habitat. This advantage was lost inBurseraandSwieteniawhen they were dispersed to younger successional habitats.At the early seedling stage, recruitment ofBurseraandSwieteniawas highest in the older secondary habitats. Seedlings ofErythrinashowed the lowest overall losses to any of the mortality factors identified during the first two months of establishment. Seeds of forest tree species arriving in secondary habitat were more vulnerable to attack by non-flying vertebrates than in mature forest. Survival of seedlings of these species was most closely related to the moisture-conserving status of the habitat.