Influence of Overstory Composition on Understory Colonization by Native Species in Plantations on a Degraded Tropical Site

background

This study evaluates forest understory regeneration in a 4.5 year-old plantation in Puerto Rico. The plantations, established in 1989, were planted on abandoned pasture in mixtures or monocultures of three exotic species: Casuarina equisetifolia, Eucalyptus robusta, and Leucaena leucocephala.

Conclusions & Takeaways

After the first two years of the plantation, the authors noted an increase in bat-dispersed species. By 4.5 years since establishment, 19 species of native and naturalized woody plants (from 14 families) were found. No woody seedlings were found in the control plots which were in unplanted abandoned pasture. The species with the highest density of regeneration were animal-dispersed (Citharexylum fruticosum, Cordia polycephala, Schinus terebinthifolius, and Calophyllum brasilense). The overstory of Casuarina equisetifolia had the lowest abundance of regeneration likely due to the dense shade and slowly decomposing litter. Regeneration density was highest in the plantations of Leucaena leucocephala which offered moderate to light shade and a readily decomposing leaf litter. However, the authors warn that Leucaena is very prolific and the seeds of the plantation trees may have a competitive advantage over native species. The authors suggest that plantation design and species selection can have an important influence on the ability of native species to regenerate. They assert that thoughtfully designed plantations can catalyze natural forest successional processes by attracting seed dispersers and improving microclimate conditions needed for regeneration of secondary successional species.