Impacts of Selective Logging and Agricultural Clearing on Forest Structure, Floristic Composition and Diversity, and Timber Tree Regeneration in the Ituri Forest, Democratic Republic of Congo

Abstract

Abstract. Mature tropical forests at agricultural frontiers are of global conservation concern as the leading edge of global deforestation. In the Ituri Forest of DRC, as in other tropical forest areas, road creation associated with selective logging results in spontaneous human colonization, leading to the clearing of mature forest for agricultural purposes. Following 1-3 years of cultivation, farmlands are left fallow for periods that may exceed 20 years, resulting in extensive secondary forest areas impacted by both selective logging and swidden agriculture. In this study, we assessed forest structure, tree species composition and diversity and the regeneration of timber trees in secondary forest stands (5-10 and ~40 years old), selectively logged forest stands, and undisturbed forests at two sites in the Ituri region. Stem density was lower in old secondary forests (~40 years old) than in either young secondary or mature forests. Overall tree diversity did not significantly differ between forest types, but the diversity of trees >10 cm dbh was substantially lower in young secondary forest stands than in old secondary or mature forests. The species composition of secondary forests differed from that of mature forests, with the dominant Caesalpinoid legume species of mature forests poorly represented in secondary forests. However, in spite of prior logging, the regeneration of high value timber trees such as African mahoganies (Khaya anthotheca and Entandrophragma spp.) was at least 10 times greater in young secondary forests than in mature forests. We argue that, if properly managed and protected, secondary forests, even those impacted by both selective logging and small-scale shifting agriculture, may have high potential conservation and economic value.

Seed and seedling survival of African mahogany (Entandrophragma spp.) in the Central African Republic: Implications for forest management

“…The installation of sawmills has transformed isolated villages into logging towns, abruptly linking them to the global economy (Robinson et al, 1999). The subsequent cascade of effects on the local environment -increased immigration, increased land conversion for agriculture, increased reliance on the forest for construction materials and non-timber forest products, and the commercialization of hunting -has been well documented and much discussed (Wilkie et al, 1992;Makana and Thomas, 2006;Zhang et al, 2006).…”

“…As with the true mahogany, Swietenia macrophylla, the highly selective ''high grade'' logging practiced throughout Central Africa often leads to regeneration and/or recruitment failure where natural regeneration is insufficient to replace harvested stems on a time scale required for sustainable timber production (Hall et al, 2003b;Grogan and Galvão, 2006). Because poorly conceived logging operations in the tropics are often the precursors to degradation and forest conversion (Plouvier, 1998;Curran et al, 2004;Makana and Thomas, 2006), it is essential that management interventions be designed to foster long-term sustainability.…”

Floristic and structural changes in secondary forests following agricultural disturbances: the case of Lama forest reserve in Southern Benin

“…"Space-fortime" analyses have been used to reconstitute temporal succession from one time spatial sequence of forest regrowth but are constrained by the assumption of the unique pathway (Kassi and Decoq, 2008). However, multivariate analyses on floristic tables, used by that method, have shown separation between secondary and primary forests plots according to their floristic composition (Makana and Thomas, 2006;Kassi and Decoq, 2008). Each particular floristic composition of secondary forests represents a pathway of secondary succession, and each particular floristic composition of mature stand represents a probable endpoint of such succession (Mesquita et al, 2001).…”

“…Scholars have considered tree density, basal area and diameter structures, as simple parameters to account for the reconstitution of forest biomass (Bonino and Araujo, 2005;Makana and Thomas, 2006). It is expected that the changes in tree size and density must be linked to competition at the cost of small trees while forest is growing (Coomes and Alen, 2007).…”

Assessment of the Diversity and Distribution of the Threatened Tree Species in a Logged Forest in Vietnam

“…After logging, the species richness is generally reduced and the composition changed in favor of pioneer trees [5,6,7]. However, human-induced disturbances in tropical forests span a wide gradient, depending on land-use type and intensity [8]. For Ashton [9], little information is as yet available on the impact of successive felling cycles in biodiverse tropical rain forests, and such research is now a critical requirement.…”