Effects of selective logging on advanced regeneration of timber species in the Asenanyo river forest reserve, Ghana

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Selective logging is the most commonly adopted method for the extraction of timber resources from natural forests in most tropical countries including Ghana. This low intensity logging system results in less damage to the residual forest and soil, and ensures sufficient regeneration but is often associated with adverse impacts on advanced regeneration and soil due to the use of heavy logging machines. However, such effects have received little scientific scrutiny. In this study, the composition and structure of advanced regeneration of timber species, and soil physico-chemical properties at varied levels of disturbance were investigated in the Asenanyo River Forest Reserve to provide insights into the effects of logging, and to help inform sustainable management of production reserves. Floristic and soil samples were collected from forty 25 m × 25 m plots randomly laid in five habitats representing three disturbance levels (i.e., undisturbed, slightly and heavily disturbed sites) and two post-logging times (i.e., 5 and 15 years). Shannon and Simpson diversity indices were somewhat higher in the slightly disturbed habitat compared to the other habitats. Means of basal area and density were significantly higher in the undisturbed and slightly disturbed sites, respectively (P < 0.05). Soil properties analyzed did not differ significantly among studied habitats with the exception of water holding capacity. Post-logging time had the highest explanatory power for the diversity indices whilst the level of disturbance best explained the evenness and density of advanced regeneration in the reserve. The basal area of advanced regeneration best explained by interaction of site and post-logging time. A non-metric multidimensional scaling ordination showed considerable similarities in species composition among the studied habitats except between the undisturbed and the heavily disturbed (15 year post-logging). Results generally suggest minimal effects of selective logging on advanced regeneration of timber species and soil physico-chemical properties. However, a slight improvement in the composition and structure of advanced regeneration in the slightly disturbed habitats reflects a positive impact of moderate disturbances in line with the intermediate disturbance hypothesis. Reducing logging disturbances that result from movements of machinery such as skidders and timber trucks, and training staff to ensure minimal adverse effect on soil and advanced regeneration, and promote sustainable timber production.
A thesis submitted to the Department of Theoretical and Applied Biology in partial fulfillment of the requirement for the award of the Master of Science degree in Environmental Science.