The contributions of a silvicultural practice (enrichment planting technique) to ecosystem restoration, management and biodiversity conservation were assessed. Data were collected from eight 25 × 25 m plots located in the three forest types (Degraded Forest, Strict Nature Reserve and Enrichment Planting Forest) in Akure Forest Reserve, Nigeria, using a systematic line transect. Soil samples were also collected in each plot at three depths. The results indicated that there were 51 tropical hardwood species distributed into 24 families in the forest ecosystem. The Shannon-Weiner indices varied from 3.25 to 2.74. Enrichment Planting Forest was discovered to have the highest number of species, genera and families when compared to the other forest types. Also, highest biodiversity indices were obtained for it. All the variables were significantly higher (p < 0.05) in the forest regenerated through enrichment planting. There was generally no significant difference in soil properties among the forest types except for total nitrogen at depths of 30-45 and 45-60 cm for SNR. The enrichment planting silvicultural practice therefore possesses the potential for soil fertility improvement, volume yield increment and restoration of degraded forests. Its use is therefore recommended for forest restoration in developing countries where anthropogenic activities have adversely affected the natural forest ecosystem.

Two important West African timber tree species with differing successional status, Mansonia altissima A. Chev and Triplochiton scleroxylon K. Schum were investigated in this study. Triplochiton scleroxylon is a pioneer species found in open forests, whereas Mansonia altissima is a nonpioneer light-demanding tree species occurring in closed forests. Amplified fragment length polymorphism markers were used to compare the genetic diversities of these two timber species in stands with different degrees of human impact (isolated forest patch, logged forest, farmland, plantation, and primary forest). Contrasting effects of human impact on genetic diversity were detected for these two timber species. The results suggested severe effects of human impact on the genetic diversity of Mansonia altissima, a nonpioneer species. However, no adverse effect was recorded in Triplochiton scleroxylon, a pioneer species. These findings indicate that nonpioneer tree species could be more prone to genetic erosion than pioneer tree species as a result of adverse human impacts. Therefore, conservation of genetic diversity in both pioneer and nonpioneer tree species populations would likely necessitate different measures.

BackgroundGlobal species extinction rates due to forest conversions are increasing. Ecologists, conservationists and governments have adopted various conservation methods. Sacred grove is one conservation option that has gained attention in recent time. We assessed understory species diversity, regeneration and recruitment potentials of four sacred groves in southwestern Nigeria. number of seedlings > saplings > overstory trees or number of seedlings > saplings ≤ overstory trees. The good regeneration status was further confirmed by the good species recruitment in the understory. Some tree species were found to be unique to some sacred groves while some species that were absent in protected forests existed in the groves. The presence of these unique tree species indicated the potential of sacred groves in conserving important tree species. The high regeneration could be attributed to strict access restrictions in the groves, and the taboos and myths feared by the people. However, the high influx of people into sacred groves for festivals and rituals, which results in trampling and burning of seedlings, is a threat to the diversity, regeneration and recruitment potentials of the groves. ConclusionHigh regeneration and recruitment status maintained in all the sacred groves in this study were achieved using taboos, cultural and traditional methods. These methods could be incorporated in managing forest reserves in Southwestern Nigeria.

Timber harvest in natural forests and its implications on carbon sequestration were investigated in the Southwestern Nigeria. Data on timber harvest from forest estates for a 3-year period were collected from the official record of States' Forestry Department. The data registered the species, volume and number of timbers exploited during the study period. The data were analyzed accordingly for rate of timber harvest and carbon value of the exploited timbers using existing biomass functions. Values were compared for significant differences among states using one way analysis of variance. The results showed that the most exploited logs, in terms of volume and number of trees, have the highest amount of carbon removal. There was a variation in type of timber species being exploited from each state. The total number of harvested trees from Oyo, Ondo, Ogun, Ekiti and Osun were estimated at 100,205; 111,789; 753; 15,884 and 18,153 respectively. Total quantity of carbon removed for the 3-year period stood at 2.3 million metric tons, and this translated to 8.4 million metric tons of CO2. The annual carbon and CO2 removal therefore were estimated at 760,120.73 tons and 2.8 million tons/ year respectively. There were significant differences (p＜0.05) in the amount of CO2 removed from the five states. Based on our result, we inferred that there is increasing pressure on economic tree species and it is plausible that they are becoming scarce from the forests in Southwestern Nigeria.. If the present rate of log removal is not controlled, forests could become carbon source rather than carbon sink and the on biological conservation, wood availability and climate change may turn out grave. For the forest to perform its environmental role as carbon sink, urgent conservation measures and logging policies are needed to be put in place.

There are over 8,000 globally threatened tree species. For each species, there is a different story behind why they are threatened and what values we stand to lose if we do not find the means to save them. Mahogany, a member of Meliaceae, is a small genus with six species. Its straight, fine and even grain, consistency in density and hardness makes it a high valued wood for construction purposes. The bitter bark is widely used in traditional medicine in Africa. The high demand for bark has also led to the total stripping of some trees, complete felling of larger trees to get the bark from the entire length of the tree and bark removal from juvenile trees. These species are now threatened with extinction due to selective and polycyclic logging, and also excessive bark removal. The natural regeneration of mahogany is poor, and mahogany shoot borer Hypsipyla robusta (Moore) attacks prevent the success of plantations within the native area in West Africa. In developing countries, most of the Khaya species exists in the wild state; therefore, the regeneration and long-term conservation are at the mercy of the vagaries of nature and the profit driven herb collectors and timber merchants. It becomes urgently necessary by government of developing countries to place ban on further harvesting of mahogany species to allow the remaining few trees of mahogany in the forest to recuperate and produce substantial seeds for regeneration.