Title:
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Ecological and genetic impacts of reduced-impact logging in the Brazilian Amazonian Forest : the case of Hymenaea courbaril L
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This study explores the present forest management systems in place and
their impact on the genetic diversity and the ecology of Hymenaea courbaril in
the Brazilian Amazon forest, specifically in the Tapaj6s National Forest. As
part of the Dendrogene Project (EMBRAPAIDFID), this study has as its main
objective to evaluate the effects of Reduced Impact Logging on the species'
genetic variability and ecological processes and to predict the likely impacts in
the short- and long-term. The specific objectives of this thesis are to verify the
quality of the. forest inventory used in RIL at Tapaj6s National Forest, to
determine impacts of harvesting on forest structure and the species'
reproductive population and spatial pattern, to determine Hymenaea .
courbarifs genetic diversity, spatial genetic structure, pollen flow and mating
system, and assess the impact of logging on these processes, and finally to
infer on the impact of logging on Hymenaea courbarifs sustainability in the
long-term using the modelling software Eco-gene. The results demonstrate
the critical importance of correct botanical identification for the sustainability of
forest management. The assessed forest inventory was highly inaccurate in
relation to botanical identification and severely underestimated trees diversity
which might compromise the capacity of accurately analysing species' spatial
distribution and forest timber stock. The results also show that current forest
management practices have negative impacts on the H. courbaril species
including a reduction in reproductive population, spatial distribution and
demography. The results of logging scenarios run through Eco-gene suggest
that the harvesting cycle for Hymenaea courbaril should be between 120 and
150 years in order to reach pre-logging levels. More importantly, the model
suggests that current logging practice strongly affect the species' population
both ecologically and genetically in the long-term. These impacts were also
observed for scenarios up to 90 years unless logging intensity is very low (10
- 30%). Moreover, the model results indicate that the current practise is not
economically viable as the volume to be logged in future harvests will be
acutely reduced. The results of this thesis provide forest planning and
management with specific scientific criteria from a heavily logged species
which can help to more effectively manage not only H. courbaril, but can also
be used to move toward the sustainability of other tree species in the Amazon
forest.
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