Influence of timber extraction routes on central African small-mammal communities, forest structure, and tree diversity

Despite increasing pressure to harvest timer from African tropical forests, the short- and long-term ecological effects of qualitative and quantitativ e variation in extraction practices rarely have been examined. At a site in the southwestern Central African Republic, we surveyed rodent and tree com munities and vegetation structure in unlogged forest and along skid trails and secondary and primary access roads at 12 and 19 years after logging. Th e most important source of variation among transects was the type of loggin g road: primary and secondary access roads showed the greatest change and s kid trails the least. An intercorrelated suite of changes occurred along th e margins of the roads, including changes in rodent community composition, increases in rodent abundance and diversity, changes in the height distribu tion of rodent abundance, increases in understory foliage density, and decr eases in sapling density and tree species richness. Ecological changes alon g the secondary roads were nearly as strong as those along primary roads, d espite the fact that secondary roads had been abandoned immediately after l ogging, whereas primary roads had been traveled up to the time of the resea rch. Continuing edge-induced effects along graded road margins at between 1 2 and 19 years after logging were indicated by differences in tree species composition, sapling and tree densities, and understory density. Our result s support conclusions of increased disturbance to rainforest communities wi th increasingly destructive road construction techniques and suggest that c anopy damage rather than stem damage is the most appropriate measure of log ging damage. Although minimizing the length of access roads is important in reducing ecological effects, it should not be achieved at the expense of i ncreased canopy damage. Rodent communities appear to be an easily measured indicator of these ecological changes and may be responsive to landscape-le vel changes in forest cover and degradation.