Artificial regeneration in gaps and skidding trails after mechanised forest exploitation in Acre, Brazil

The natural regeneration of some desirable species under exploitation pressure in Amazon is often very poor or non-existent. The traditional techniques of enrichment planting have presented low performance of the planted seedlings and high costs for its implementation. This study analyzes the first 5 years of growth and survival of five tropical tree species (Bertholletia excelsa, Ceiba pentandra, Torresia acreana, Swietenia macrophylkla and Cedrela fissilis) planted in skidding trails and exploitation gaps. The basic planting technique consisted in using the cleared areas after forest harvesting for the establishment of seedlings of species ecologically adapted to the gap environment. The study was carried out in the EMBRAPA-CPAF-ACRE (Agroforestry Research Centre of Acre) in Acre State in West Amazon. The diameter increment varied from 0.30 cm year(-1) for Bertholletia to 0.52 cm year(-1) for Swietenia and Torresia. After 5 years the height growth was similar for all species around 3.0 m. In the first year Bertholletia presented a high mortality, around 80%, caused by severe predation by rodents. Ceiba also presented a high mortality after the second year of planting probably due the canopy closure. The best survival percentage was presented by Torresia, over 90%. The Meliaceae (Swietenia and Cedrela) species had a similar survival, around 70 to 75%. The Hypsipyla grandella attack was more severe in Cedrela than in Swietenia, but in both cases (9.37 and 31% after 7 and 5 years respectively for Swietenia and Cedrela) was still low when compared with other enrichment plantings. (C) 2000 Elsevier Science B.V. All rights reserved.