Scholarly works in Social and Environmental Forestry
Permanent URI for this collectionhttps://repository.ui.edu.ng/handle/123456789/13518
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Item Optimising Sampling Design with Semivariogram for Vegetation Survey of Derived Savannah, Ogun State, Nigeria(unique scientific publishers, 2024) Banjo, O. B.; Akintunde-Alo, D. A.; Ige, P. O.Vegetation survey is useful for biodiversity conservation and management. Sampling design strategies oftentimes fail to capture the heterogeneous vegetation structure of area being studied due to cost and time constraint. The study aimed to determine the optimum sampling design for vegetation assessment in the study area by characterizing spatial structure and identifying extent of spatial correlation in data points. Hypothetical sampling scenarios of low, medium and high density random and transect sample plots of (3 x 3 km) were laid on Normalised Difference Vegetation Index (NDVI) from Landsat 8 Operational Land Imager (OLI) satellite imagery of the study area. NDVI values were extracted for the respective sampling scenarios. Data were subjected to descriptive statistics and fitted to spherical, exponential and Gaussian’s semivariogram models. Best fitted models were evaluated by Root Mean Square Error (RMSE) values. Nugget, sill and range parameters of the best fitted semivariogram models described the spatial structure of the vegetation cover in the study area. Therefore, the parameter estimates guided the selection of medium density random sample plots and low density transect-laid sample plots as the optimized sampling design most suitable for vegetation survey in derived savannah ecosystem of Ogun State, Nigeria.Item Stand growth, Biomass and Carbon sequestration potentials of Parkia biglobosa (jacq.) Bench plantation in South-Western Nigeria(Joint Coordination Centre of the World Bank assisted National Agricultural Research Programme (NARP), 2024) Akintunde-Alo, D. A.; Onilude, Q. A.; Ige, P. O.; Adeoti, O. O.This study assessed tree growth variables, above (AGB), below ground biomass (BGB) and total carbon content (TC) sequestered by Parkia biglobosa (Jacq.) Bench. Plantation in Wasangare, Oyo State using nondestructive ground base survey. Tree growth data (Diameter at breast height, Dbh and Tree height, Th) were collected using lacer ace hypsometer and diameter girth tape from 20 temporary sampling plots of size 25 m X 25 m established through systematic transect lines. Diameter size classes (DSC) for the plantation was examined, carbon stock for each DSC was also determine while basal area (m2 ha-1), volume (m3 ha-1), Biomass (Mg ha-1) and Carbon (Mg ha-1) were also estimated. Results showed mean Dbh of 18.7 + 0.25 cm with 8.14 + 0.10 m, 0.033 + 0.00 m2 ha- 1 and 0.320 + 0.01 m3 ha-1 for tree height, basal area and volume respectively. AGB and BGB were 10.877 + 0.39 Mgha-1 and 2.175 + 0.08 Mgha-1 respectively while TC was 6.527 + 0.24 Mgha-1. The percentage carbon stock proportion for each DSC revealed class size 25-29-9 cm (19.02%) as the highest while the least proportion was observed in less than 5 cm class with 0.04% of carbon. The DSC showed majority of the tree Dbh in lower Dbh classes with fewer trees in higher classes forming almost a normal bell shape. The study provides information that can help the management in planning silvicultural activities and selective removal from the stand (harvesting schedule). Tree Dbh, height, basal area, volume and biomass are the determinant characteristics for forest carbon assessment. In conclusion, the plantation actively sequesters carbon showing potentials for indigenous trees in climate change mitigation.Item Development of Silvicultural Management Models for Gmelina arborea Roxb. Stands in Area J4, Omo Forest Reserve, Nigeria(Forest and Forest Products Society, 2021) Aturamu, O. A; Alo A. A.; Ige, P. O.Plantation establishment of fast-growing species such as Gmelina arborea has been suggested as a quick fix to the perennial problem, especially in Omo Forest Reserve. Management models have been identified as tools for sustainable management and monitoring of Gmelina plantation. Hence, silvicultural management models were developed for sustainable management of Gmelina plantation in Omo Forest Reserve. Nine Gmelina arborea age series (34, 32, 30, 26, 24, 22, 20, 18 and 16 years old) stands were purposively selected in Area J4 of Omo forest reserve. A total of Sixty-five temporary sample plots were demarcated proportionate to size across the age series. In each plot, diameter at breast height and stem height were measured to estimate stand basal area and volume. Silvicultural management models were developed to estimate the optimum rotation volume, area and number of stock to harvest using the linear programme option of the R package to obtain the solutions of the planning model for 20 years at 5 years period. It was observed that the mean tree dbh and stem height ranges from 21.50 to 70.61 cm and 16.08 to 24.98 m respectively. The mean basal area and stem volume had the respective values which range from 33.31 to 413.78 m2/ha and 423.19 to 8413.52 m3/ha. At the individual tree level, mean annual growth is attained at 27 years. This represents the optimal rotation age of any Gmelina arborea stand in Omo forest reserve. If selective logging is applied for timber purpose, a rotation age of 27 years will be the appropriate rotation age. However, if clear-felling is opted for, the appropriate rotation age will be 25 years. The logging plan that optimizes volume in terms of area cut in each stand and period revealed that in 16 years old stands, whole logging will take place only during the last period of the plan, removing 5.00ha. The respective area to be cut during the 1st, 2nd, 3rd and 4th periods are 451.70ha, 517.50ha, 250.80ha and 140.00ha. The harvesting schedules obtained in this study have shown that the management planning model provides rational and practicable results.