Scholarly works in Social and Environmental Forestry

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    Equations for estimating bark thickness of Gmelina arborea (ROXB) trees in Omo forest reserve, Nigeria
    (Ministry of Agriculture and Livestock Development, Nepal, 2018) Alo, A.A.; Ogana, F.N.
    The measurement of bark thickness is an important factor for computing inside bark volume of a standing tree or log. Bark thickness at breast height can easily be measured. However, when bark thickness at relative height of a standing tree is required, the application of equations becomes imperative. In this study, equations were developed for estimating bark thickness at relative height and at breast height. Stratified random sampling was used to establish 50 sample plots of 0.04 ha size across 10 age series in the Gmelina arborea plantation in Omo Forest Reserve, Nigeria. Eight equations for estimating bark thickness as function of diameter inside bark (dib) and Relative Bark Thickness (RBT) were developed. Equation was also developed for predicting absolute bark thickness at breast height. The equations were assess based on Root Mean Square Error (RMSE), Mean Absolute Bias (MAB), Akaike Information Criterion (AIC) and Shapiro-Wilk test of normality. The results showed that six out of the nine equations performed relatively well in estimating bark thickness. The best equation for estimating bark thickness as function of dib had RMSE, MAB and AIC values of 0.065, 0.049 and -125.989, respectively. The best equation for RBT had 0.109, 0.079 and -75.577, respectively. The equation for absolute bark thickness at breast height had 0.204, 0.152 and -12.697. The equations did not violate the assumption of normality as revealed by normality test (p > 0.05). With these equations, any analytic volume equation can be used to compute the inside bark volume of the standing trees. The relative back thickness and diameter inside back functions developed in this study were found to be satisfactory based on the various criteria used for their assessment. Thus, they are recommended for use in estimating the back thickness and diameter inside bark of Gmelina arborea stands in similar ecosystem.
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    "Yields and nutrient pools in soils cultivated with Tectona grandis and Gmelina arborea in Nigerian rainforest ecosystem"
    (King Saud University, 2011) Adekunle, V.A.J.; Alo, A.A.; Adekayode, F.O.
    This study examined the yield of the two most prominent exotic species in southwest Nigeria and the nutrient status of soils cultivated with these species. The impacts of plantation development on soil nutrients were also examined. The plantations species are Gmelina arborea (Gmelina) stands established in 1984, 1988, 1990 and 1994 and Tectona grandis (Teak) established in 1990, 1992, 1994, 1996 and 1997. Growth data and composite soil samples from 3 depths (0–15, 15–30 and 30–60 cm) were collected from five equal sized plots (20 • 20 m2) randomly located in the plantation of the two species. Also, soil samples were collected from the adjacent natural forest for comparison. The results for both species show that tree growth variables increased substantially with increase in tree age. There was significant difference in number of trees per hectare, dominant diameter, volume/ha and MAI for the Gmelina stands. In the Teak stand, there was significant difference in most of the tree growth variables also. Nutrients required by plants to survive were present in the soil samples from the plantations and the natural forest in different proportions. There was high correlation between percentage sand and most of the tree growth variables for both species. The pH value obtained for the Gmelina stands ranged between 6.47 and 7.47 while that of Teak stands ranged between 5.57 and 8.33. There was also a high and positive relationship between