Journal of Tropical Ecology

Research Article

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

D. S. Hammonda1 p1

a1 School of Environmental Sciences, University of East Anglia, Norwich NR4 7TJ

ABSTRACT

Vertebrate attack accounted for 98.4% of all seed loss during the two months following dispersal. This accounted for, across all habitat types, 94% of Bursera, 76% of Spondias, 37% of Swietenia and 25% of Erythrina seeds artificially dispersed. Bursera, Spondias and Swietenia seeds in early successional habitat suffered significantly greater predation than in either older abandoned (30 y) or mature forest plots. Erythrina showed 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 of Bursera and Spondias were 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 in Bursera and Swietenia when they were dispersed to younger successional habitats.

At the early seedling stage, recruitment of Bursera and Swietenia was highest in the older secondary habitats. Seedlings of Erythrina showed 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.

(Accepted June 03 1994)

Correspondence:

p1 Present address: Department of Pure and Applied Biology, Imperial College – Silwood Park, Ascot, Berks SL5 7PY, UK.