Vegetative propagation of native tree species: an alternative restoration strategy for the tropical Andes

Abstract

Pastures in the Neotropics are usually planted with exotic forage grasses, which are one of the most challenging barriers to the restoration of tropical forests. We evaluated the efficacy of vegetatively planting large stakes or cuttings (approximately 2 m) of four tree species (Brugmansia arborea, Erythrina edulis, Ficus americana, and Trichanthera gigantea) in areas dominated by three common exotic pasture grasses previously used for forage (Cynodon nlemfuensis, Melinis minutiflora, and Pennisetum clandestinum). We monitored stake survival and growth metrics (e.g. height, diameter at breast height, and crown area) for 12 months and quantified changes in forage grass biomass during the same period. We evaluated how initial diameter of planted stakes, exotic grass species, and species identity influenced stake survival; the degree to which planting stakes reduced exotic grass biomass; and assessed interspecific stake survival, growth, and morphological parameters (crown area, number of resprouts). Across all forage grass treatments, E. edulis and B. arborea had the highest survival (81 and 64%, respectively) and growth in terms of height (2.2 and 1.8 m) and crown area (0.74 and 0.60 m2). Stake survival was strongly influenced by species identity and the exotic grass species into which stakes were planted. Survival was also tied to initial stake diameter, but to a much lesser degree. The biomass of the forage grass P. clandestinum was reduced by 45% in plots where E. edulis was planted, and by 18% in plots planted with B. arborea. Planting vegetatively propagated trees in the tropical Andes can help facilitate forest recovery by establishing woody vegetation that outcompetes aggressive forage grasses and improves conditions for plant community reassembly.