DEPARTMENT OF FOREST RESOURCES MANAGEMENT
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Item Tree species coexistence and diversity on elevation gradient of elephant camp natural forest, Nigeria(Scientific and Academic Publishing, 2022) Falade, O. F.; Babalola, T. D.Spatial species diversity and size inequality contribute to maintenance of tree species diversity in tropical forests. Coexistence of tree species requires interactions within and between spatial species and size diversity. However, elevation gradient has significant impact on growth and species interactions. Failure of most conservation efforts is due to inability to identify and maintain coexistence mechanisms existing in the forest. Understanding the contribution of elevation gradient to coexistence of tree species will improve conservation efforts and terrestrial carbon budgeting. Therefore, association between tree diversity and size inequality on elevation gradient of Elephant Camp Natural Forest was investigated. Eight (30m x 30m) plots were systematically demarcated on 1km line transects in each identified elevation (Hilltop and Valley-Bottom stands). Trees diameter-at-breast height (dbh) were enumerated and identified to species level. Tree dbh was measured and density estimated. Tree species diversity (Shannon-Weiner, Simpson and Margalef indices) and size inequality (Gini coefficient, skewness and Coefficient of variation) were computed. Stem volume and biomass were computed and converted to biomass carbon. Data collected were analysed using descriptive, correlation analysis and principal component analysis. Tree density varied from 435/ha to 767/ha. There was positive correlation between Skewness and Gini coefficient in Hilltop stand and negative correlation between Skewness and Simpson index in Valley-Bottom stand. The measures of tree size inequality and species diversity were strongly associated with each other in Valley-Bottom stand and not in Hilltop stand. Structural diversity and species diversity determined the competitive interaction among tree communities in Hilltop and Valley-Bottom stands, respectively.Item Structural diversity of tree stems of elephant camp natural forest in Omo Forest Reserve(MDPI, 2021) Falade, O. F.; Iheke, J. U.Tree size diversity is an indicator of biodiversity values of a forest. Microsite conditions of a forest determine the survival and growth of trees. However, the contribution of variable habitats to tree size hierarchy and segregation is poorly understood. Tree size variation in a population is caused by different competition mechanisms. Therefore, the size distribution and spatial pattern of trees can identify the process governing resource utilisation in the forest. The objective of the study was to investigate the tree stem structural diversity in the Elephant Camp natural forest in the Omo Forest Reserve. Three and four 0.09 ha sample plots were established in Riparian (RF) and Old-growth forests (OF) in the Elephant Camp natural forest, respectively. The tree stems (Dbh ≥ 5cm) were identified to the species level and enumerated within each plot, and the stem density was computed. The diameter at breast height (Dbh) was measured with diameter tape. Species diversity was assessed using Shannon–Weiner (H’) and Simpson indices (1-D’), while size inequality was assessed using the Gini coefficient (GC), coefficient of variation (CV), H’ and I-D’. The performance of single two- and three-parameter Weibull models was evaluated using Kolmogorov–Smirnov (K-S) chi-square (χ2), root-mean-square error (RMSE), bias and the coefficient of determination (R2). Data were analysed using descriptive statistics. A total of 27 and 24 tree species were identified in RF and OF, respectively. The stem density of RF was significantly higher than that of OF. The values of species diversity (H’, 1-D’) and evenness (E’) were higher in OF than in RF, while richness (Margalef and number of species) was higher in RF than in OF. The Dbh was 38.30 ± 21.4 and 42.87 ± 19.2 cm in Riparian and Old-growth forests, respectively. Size-density distributions of both forests were positively skewed and expressed exponential pattern. The forest types of the Elephant Camp natural forest comprise the same size-density frequency shape but a different proportion of tree sizes and structural diversities.