Tree height-diameter relationship can be used as an important input component in forest growth and yield models, and description of stand dynamics. Five nonlinear growth functions were fitted to tree height-diameter data of a 21-year-old Gmelina arborea plantation in Ibadan, Nigeria. The data consisted of three sets obtained in 2004, 2008 and 2011 for total tree height and diameter at breast height (DBH). According to the model statistics, the five growth functions fitted the data equally well, but resulted in different asymptote estimates. Modified exponential fit was observed to give the best fit for the three data sets based on least square error, coefficient of determination and significance. The predicted values follow the same nonlinear pattern and formed close to the line of best fit without much outlier. The result of this study revealed that the ability of DBH in determining height is not strong enough based on the model's goodness of fit and the model's ability for predictive purposes. Hence, more variables such as age, crown area and soil fertility were recommended to be incorporated in future prediction of the tree height in the study area.

This study examines the effects of population growth on deforestation in Nigeria between 1991 and 2016. Anthropogenic factors especially population growth were identified to be the major forces responsible for deforestation in Nigeria. The Augmented Dickey Fuller (ADF) test was used to establish stationarity among the variables and the Johansen cointegration test was used to establish a long run relationship between population growth and deforestation in Nigeria. Population growth was found to have a negative effect on the available forest cover in Nigeria. The study therefore recommends the development of rural areas, enactment of policies aimed at reducing population growth and sensitization to protect the available forest resources in Nigeria. Keywords: forests, deforestation, population growth

An inventory of the entire tree species ≥10cm diameter at breast height (dbh) was carried out within Forestry Research Institute of Nigeria (FRIN) investigation 133 Shasha in Osun State, Nigeria. This study was carried out to ascertain the tree species diversity, conservation status and utilization potentials in the study area. The results were obtained from 16 sample plots of 50×50m in four tracts located through cluster sampling technique. In all, an average total of 295 stands distributed among 66 tree species and 28 families were encountered. High value of Shannon-Weinner index H'=3.73 and Evenness of E=0.89 were obtained for the reserve. At present, only few trees have attained the merchantable size of 48cm dbh. The 63 tree species in the study site were categorized into four groups namely, stable, vulnerable, endangered and threatened status. The result revealed that stable group had 1.59%, vulnerable 4.76%, endangered 44.44% and threatened 49.21%. Result of the Utilization potentials revealed that utility classes 7 - 8 accounted for 55.6% (comprises of tree species with no potential use for sawn timber), while 45.4%. of trees in classes 1 – 6 comprises of trees with timber potentials. This study highlighted species population diversity, conservation status and utilization potentials of the study site and called for ecological application in the management of forest reserves in Nigeria.

Education spreads its tentacles to all areas of life; it is the bedrock of socio-political and economic development. This study was conducted in two of the NIHORT's adopted villages namely Egbeda and Baayaoje established in 1997 in Oyo State, Nigeria to investigate whether the training given to the community members on the method of agroforestry practices actually yielded any positive impact within the last 10years. The training given includes rapid multiplication of seedlings, crop processing and utilization, cultivation and integration of different crops on a piece of land, and farm records keeping. Data obtained were analyzed using Cobb Douglas production function and other relevant statistical estimators. Factors responsible for the adoption of this farm practice among the trainees includes land availability, willingness to accept the farming technology training attendance and others. The impacts of agroforestry education on these communities were made manifest in the form of improved environmental protection and increased revenue generation. It is suggested among others that government should promote and prioritize education/training among rural people; this will serve as a tool of communicating and disseminating research findings and policies to the rural populace for speedy growth and sustainable development.

This experiment examined the impact of management techniques for sustaining the forest soils nutrient status using a comparative study of soil chemical and physical properties of different forest types in Onigambari Forest-Reserve. Soil sampling was conducted in two sections representing two forest types; Tectona grandis (TG) plots and the natural vegetation (NV) within Onigambari Forest-Reserves. Each section, segmented into a 10m-by-10m quadrat size. Twenty samples were collected at random in each plot in quadruplicate from the surface (0-15cm) and subsurface (15-30cm) depth. The composite samples were air-dried, prepared for physical and chemical analyses. Data collected were subjected to ANOVA, means were compared using student’s t-test (p ≤ 0.05) using JMP Pro 14. The results showed that the means of chemical and physical properties in both forest plantations varied with depth. The pH increases with depth from 5.95 to 6.15 in TG and 6.15 to 6.25 in NV forest at 0-15cm and 15-30cm, respectively. However, NV had the highest amounts of organic carbon content, Total-Nitrogen, and exchangeable cations decreased with depth at both forests. Phosphorus content increased from 9.43(0-15cm) to 10.95(15-30cm) at TG forest and 2.7 (0-15cm) to 5.9 (15-30cm). Sand content was higher at the TG forest, while higher clay and silt contents were observed in NV. Organic-matter and organic-carbon content were observed to be higher in the surface layer compared to the sub-surface layer in both forests studied. In conclusion, the Natural vegetation soils possess more nutrients than Tectona grandis soils. Therefore, afforestation should be encouraged.