Responses of Miombo to harvesting: Ecology and management

摘要

This study was undertaken to assess the effects of wood harvesting for energy on the miombo ecosystem and to determine factors that promote or constrain the recovery and productivity of miombo after felling. The study was carried out in dry miombo woodland in the Chakwenga area in central Zambia. It was not possible to replicate the study in wet miombo woodland which occurs in the northern parts of the country. Although this limits the application of the findings, the management implications are relevant to both types of miombo. Harvesting for charcoal production in miombo woodland removes about 50% of the wood biomass and this has no significant effect on soil productivity. Top soil moisture regime and nutrient stocks were similar in cut and uncut plots two years after cutting. Wood carbonization at the kiln sites increased soil pH, exchangeable phosphorus and potassium and cation exchange capacity but had no effect on other soil chemical properties. Miombo productivity was correlated to tree density and soil fertility. Tree density was several-fold higher in regrowth than old-growth miombo and this increased with each successive cutting. Productivity was highest at a site that had been clear-cut three times in the past 20 years. High light intensities appear necessary for rapid growth of old seedlings and saplings. Such levels of radiation are achieved by clear-cutting although isolated trees have little effect on such growth. The concern about dry miombo ecosystem degradation due to deforestation caused by charcoal production is not supported by the results of this study. If recruitment into regrowth miombo from the seedling pool after each cutting is not balanced by recruitment into the pool, biodiversity conservation may be endangered. This should be considered in determining rotation periods. 93 refs, 31 figs, 63 tabs