This study undertook ecological and institutional analyses in four Tanzanian montane forests and adjacent villages, with the goal of elucidating policy-driven differences in local institutional arrangements for forest management, anthropogenic forest disturbance patterns, and ensuing changes in forest structure and composition. Outcomes are contrasted among centralized, comanaged and communal forest management situations, in the fragmented landscape of the West Usambara Mountains, part of the Eastern Arc Mountains biodiversity hotspot. An adjacent, minimally-disturbed research forest served as an ecological reference for comparison of forest results to that expected for a montane forest absent significant anthropogenic disturbance over the past 100 years.
Forest management strongly relates to issues of illegal logging in the study area, while ecological effects of cryptic selective logging and post-logging successional trajectories are poorly known. I additionally evaluated differences in biomass densities, forest structure and species composition among unlogged old-growth and two highly selective logging intensities typical for the region: (1) short term logging over a 9 year period, now 17 years into recovery; and (2) 50 years of ongoing logging.
The study explores substantive challenges for achieving decentralized forest management goals in human-dominated landscapes, finding that the communal management strategy showed comparatively stronger local institutional functioning, reduced illegal logging, and better conservation of forest integrity, while also demonstrating linked livelihood-conservation dilemmas common to both institutional models with local community participation. Communal forest outcomes demonstrated the importance of tenure security and management autonomy in successful devolved management.
Evaluation of selective logging effects on forest structure concluded that the cumulative effect of 50 years of ongoing highly selective non-mechanized logging has been increased dominance by species of high wood density in conjunction with a massive decline in the targeted medium wood density species Ocotea usambarensis , a structural shift towards dominance by many small trees and few large trees, but little change in broad measures of forest structure like overall basal area and biomass. Broad similarities in structure and species occurrence masked more subtle but fundamental differences among different anthropogenic disturbance intensities.
