Early species selection for tropical reforestation: A consideration of stability

Third year growth data from a species screening trial established by the Organization for Tropical Studies (OTS) at the La Selva Biological Station in Puerto Viejo, Heredia, Sarapiquí, Costa Rica from 1987 to 1990 serve as the basis for analysis. Both exotic and native timber species were tested for survival, growth, and form. The species x site sum of squares was partitioned in order to identify high yielding species that are generalists and high yielding species that may be specialists. The contribution of each species to the species x site interaction term was determined: four species were found to contribute 61% of the interaction ( Ochroma pyramidale, 26.5%; Gmelina arborea, 13.1%; Terminalia superba, 11.2%; and Acacia mangium, 10.3%). If three additional species are added ( Pseudobombax septenatum, 9.4%; Terminalia amazonia, 8.7%; and Terminalia ivorensis, 7.4%) 86% of the species x site interaction effect is explained. If each species contributed equally to the variance, each would have an ecovalence of 4.55%. Three stable species with above average tree volume ( Vochysia guatemalensis, Jacaranda copaia, and Goethalsia meiantha) show potential for reforestation over large regions where plantation maintenance is minimal. The identification of several high yielding unstable exotic species helps to explain their uneven success in plantations in Costa Rica. Some lower yielding, but more stable, native species may offer greater yields where site conditions are poor and maintenance limited.