Enrichment planting in a tropical secondary forest in Veracruz, Mexico.
The first 8 years of growth and survival of 4 tropical tree species planted under different levels of canopy closure were analysed. Three canopy closure levels were established in a 10-year-old secondary forest by removing different canopy layers which gave 17, 37 and 68% of light transmission. All species showed the highest growth rates with the 68% light transmission treatment, among which Cordia alliodora was the fastest-growing species. The lowest survival rate was observed with the 17% treatment in Cordia alliodora and Swietenia macrophylla, while Brosimum alicastrum displayed the lowest survival rate in the open. Cedrela odorata had almost 100% mortality in all treatments and for this reason was left out of the analysis. Primary forest species (B. alicastrum) and late secondary forest species (S. macrophylla) displayed lower growth rates and showed smaller differences in growth within the treatments than secondary forest species (C. alliodora). The experiment was particularly helpful in assessing the possibility of manipulating secondary forest canopies to optimize growth and survival of species introduced in enrichment planting schemes. It was also concluded that it is advisable to plant both primary or late secondary forest species together with secondary forest species, which permits full exploitation of the environment. From authors' summary. KEYWORDS: TROPAG | Cordia alliodora Swietenia macrophylla Brosimum alicastrum Cedrela odorata | Miscellaneaous Crops and Forestry | forest trees | growth rate | light | canopy | secondary forests | Mexico | Veracruz.