Forty Years of Tropical Forest Recovery from Agriculture: Structure and Floristics of Secondary and Old-growth Riparian Forests in the Dominican Republic1

Abstract

Interest in tropical secondary forests has grown as large areas of agriculture have been abandoned in recent decades; yet, there are few long-term studies of post-agriculture vegetation recovery in the tropics. In this study, we compared the vegetation structure and floristic composition of old-growth and 40-year-old secondary riparian forests in the Cordillera Central, Dominican Republic. Canopy height and stem density of woody plants were similar between forest types, but basal area of trees was 27 percent lower in secondary forests. Introduced tree species comprised 20 percent of the basal area and dominated the understory of secondary forests. Life-form diversity was higher in old-growth forests as arborescent ferns, the palm species, and epiphytic bromeliads, orchids, and bryophytes were much more abundant. The number of species of epiphytic orchids and bromeliads, ground ferns, and herbaceous plants was also significantly higher in old-growth forests. The species density of woody plants and vines, however, was comparable between forest types, and vine abundance was significantly higher in secondary forests. The high importance of introduced tree species and the delayed recovery of several plant life-forms have important implications for the conservation of plant diversity in secondary forests in the tropics. The robust regeneration of woody structure despite the long land tenure (ca 60 yr) by farmers is probably due to the nutrient-rich alluvial soils and low-intensity agriculture. This study revealed the potential for the rapid recovery of woody plant diversity and structure in fertile secondary forests adjacent to mature forest seed sources and the more delayed recovery of nonwoody plant diversity and abundance.