PRELIMINARY ASSESSMENT OF THE EFFECTS OF LOGGING ON THE COMPOSITION AND STRUCTURE OF FORESTS IN THE VENEZUELAN GUAYANA REGION

Some effects of logging on the composition and structure of lowland ra inforests in the Venezuelan Guyana Region (Imataca Forest Reserve, Bol ivar State) are evaluated. The diagnosis comprises two of the main act ivities included in forestry management plans designed for this region : selective extraction of trees and establishment of silvicultural enr ichment strips. The disturbance of primary forests by cutting and mech anized carrying of logs, as well as the opening of extensive gaps in s ome sectors associated with those activities, produce a modification i n the forest's physiognomic matrix, as a consequence of I) deforestati on of areas for gathering and transportation of wood, 2) fragmentation of forest masses, 3) interruption of canopy continuity in those selec tively logged areas with the highest levels of disturbance; and 4) sub stitution of forest vegetation by communities of shrubs and grasses, w here colonizer species are the dominant components. Internally, forest s under. exploitation were typified by. I) less coverage; 2) higher in cidence of light at the lowest strata; 3) increase in density of veget ation at the understory level; 4) higher abundance of fallen rr trunks and truncated trees, 5) decrease in the abundance of vines during fir st stages of succession, and 6) reduction in density of trees in all d iametric categories, in magnitudes proportional to their relative abun dances. Additionally, silvicultural enrichment strips promoted the ext raction of an average of 1,186.5 trees/ha ((3)10 DBH) that represented at least 97 species, which, were discarded in the surrounding foreste d sectors, being substituted by plantations of tr ee species with a ra pid growth rate and a high demand in the forestry industry. Tendencies of these results show that the extractive methods used in the study a rea, although are theoretically selective, produce a negative impact o n all the components of the remaining arboreal strata, decreasing the regenerative potential of the forest and ifs ecological value as a res ource supplier for animal communities. Some implications of these aspe cts for the management of wood producer areas are discussed, with reco mmendations to conserve biological diversity in logged forests of the Venezuelan Guyana Region.