The effects of non-timber forest product cultivation on the plant community structure and composition of a humid tropical forest in southern Mexico

Abstract

The planting of non-timber forest products (NTFPs) in the understory of tropical forests is promoted in many parts of the world as a strategy to conserve forested lands and meet the economic needs of rural communities. While many studies of NTFP management have focused on the effects of harvesting on wild populations, the impacts of understory NTFP plantations, or enrichment plantings, on forest community composition and structure have not been investigated. We assessed the effects of understory plantations of the palm Chamaedorea hooperiana Hodel, on community composition and structure of an old growth tropical rain forest in the Los Tuxtlas Biosphere Reserve in southeastern Mexico. A blocked design consisting of four C. hooperiana plantation sites each paired with an adjacent site of unmanaged forest was used to compare the plant species richness and diversity, stem density, basal area and size class structure in plantations versus unmanaged forest. In each site, 12 10 m diameter plots were established for a total of 96 plots (4 blocks × 2 sites × 12 plots). Although the stem density, diversity, richness and basal area of large overstory trees (≥20 cm dbh) were unaffected by the establishment and management of understory palm plantations, the stem density, species richness and basal area of woody species in smaller size classes (<10 cm dbh) were significantly lower in plantation sites than in similar unmanaged forest sites. The density of naturally occurring, economically valuable palm species was unaffected by the C. hooperiana plantations, indicating that these understory species are spared when plantations are established and maintained. However, plantation sites showed significant reductions in the density of the midstory palm Astrocaryum mexicanum, the most abundant plant in unmanaged forest sites. The removal of vegetation in NTFP plantations may result in the fragmentation and/or elimination of local populations of understory and midstory plant species. In addition, changes to the composition of advanced regeneration due to the removal of canopy tree seedlings and saplings may have implications for future patterns of forest regeneration and composition. Nonetheless, NTFP cultivation offers a promising alternative to more destructive forms of land uses in the tropics and warrants further attention as a forest management strategy.