Effect of abandoned exotic and native species plantations on the natural regeneration of a montane forest in Colombia

Vegetation surveys were carried out during 1994 in 0.1. ha plots in abandon ed plantations of Pinus radiata, Cupressus lusitanica, Eucalyptus globulus, Alnus acuminata and in a secondary upper montane rain forest in the Centra l Andes of Colombia. The regeneration forest had the higher number of plant species (33) followed by the E. globulus (26) and A. acuminata (16) planta tions. Abandoned plantations of P. radiata and C. lusitanica, had only thre e species. There were only eleven species in common between the regeneratio n forest and the plantation of E. globulus (Baccharis latifolia, Cordia cyl indrostachya, Dunalia solanacea, Leandra melanodesma, Lippia hirsuta, Monni na angustata, Solanum aff scorpioideum, S. aphydendron, Sphaeropteris quind iuensis, Tobouchina mollis and Verbesina nudipes), and only seven when comp ared to the A. acuminata plantation (Abatia parviflora, Asploddianthus pseu dostuebelli, Bocconia frutescens, Leandra melanodesma, Lippia hirsuta y Sol anum aff. scorpioideum y Verbesina nudipes). With the exception of Cordia c ylindrostachya, Bocconia frutescens and Tibouchina mollis, all other specie s are understory shrubs dispersed by wind or birds. In the understory of th e P. radiata plantation there was abundant regeneration of the Colombian na tional tree, Ceroxylon quindiuensis. Tree height and basal area were signif icantly higher in the P. radiata and C. lusitanica plantations than in the regeneration forest. Of the environmental and biological variables measured in this study, the accumulation of needles under P. radiata and C. lusitan ica plantations, and the high biomass of fine roots under the C. lusitanica plantation, could be the main limiting factors for the establishment of a higher number of species of the native forest. The chemical properties of t he soils varied;greatly, and there were no consistent differences between t he soils under exotic and native species.