DEPARTMENT OF FOREST RESOURCES MANAGEMENT
Permanent URI for this communityhttps://repository.ui.edu.ng/handle/123456789/457
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Item Some of the mechanisms for coexistence of tree species diversity in tropical forests: a review of effects of tree density dependence(Scientific Research Publishing, 2023-01) Falade, O. F.Tree communities contribute to maintenance of species diversity in tropical forests. Coexistence of many tree species is not without competition. Therefore, coexistence of tree species and size diversities occur sequentially or simultaneously in tropical natural forests. Understanding coexistence and competition mechanisms of tree species requires knowledge of interactions within and between species. However, many conservation efforts and strategies failed due to inability to identify and maintain functional coexistence mechanisms among tree species in the forest. Also, most trees died because of pressure on their habitats and not because of limiting growth resources. Hence, species identity, minimum distance and size of the neighbouring trees which are responsible for coexistence of competing trees in most tropical forests have not been explicitly reviewed. Therefore, this review evaluated some of the density dependent mechanisms for coexistence of tree species alpha diversity in tropical forests. Many interactive mechanisms are responsible for coexistence tree species in tropical forests. Inter- and intra-specific competitions are the most significant and both facilitate positive and negative density dependence. Therefore, switching from negative to positive density dependence may occur in some situations. Positive and negative density effects regulate species abundance and coexistence through conspecific and heterospecific structures. Aggregates of conspecific and heterospecific neighbours constitute forest spatial structure. Negative density interactions are mutually exclusive and basically ranged from effect of species identity of neighbours, distance to neighbours and tree size of the neighbours to reference trees in the community structures. Some mechanisms shorten distances for heterospecific than conspecific interactions. Conspecific structures improved survival and growth of rare tree species. Interactive mechanisms in tree community and population structures facilitate species diversity and size inequality, respectively.Item Tree species and size diversity of Akure Strict Nature Reserve, Nigeria(Science Publishing Group, 2023) Falade, O. F.; Aruwajoye, D. A.Size and species structures control the natural mechanisms maintaining high structural diversity. Use of size inequality and species diversity measures singly for conservation decisions brings about inconsistent results. Therefore, most conservation efforts fail due to lack of understanding of mechanisms promoting coexistence of tree species. However, relationship between size inequality and species diversity indicates the natural mechanism promoting coexistence of high species diversity. Therefore, this study investigated the relationship between tree size inequality and species diversity in Akure Strict Nature Reserve. Eighteen and twelve plots (30m x 30m) were laid on parallel transects of 3.60km long and 50m width in Old-growth and Riparian forests, respectively. Trees with diameter-at-breast-height (dbh) ≥ 10cm were counted and identified to species level. Tree diameter at base, middle and top and total height were measured using girth tape and Relaskop. Tree species diversity (Shannon-Weiner; Simpson; Margalef indices) and dbh inequality measures (Gini coefficient, Gini; Coefficient of Variation, CV; Skewness Coefficient, Skewness) were computed and compared. Stem biomass were computed and converted to carbon stock. Data were analysed using descriptive, and correlation analysis at α0.05. Fifty-five (56) tree species representing 17 families were found in the forest. Species diversity indices were higher in Riparian while size inequalities in Old-growth forests. GC correlate with Shannon-Weiner (r=0.54; n=18, p≤0.018) and Margalef (r=0.473; n=18, p≤0.04) in Old-growth while GC correlate with CV (r=0.716; n=12, p≤0.09) in Riparian forests. The size inequality measures were strongly related with each other in Riparian while species and size inequality measures were strongly related with each other in Old-growth forests. The carbon stocks of Old-growth and Riparian forests were 117.21Mg/ha and 43.47Mg/ha, respectively. Triplochiton scleroxylon and Bridelia micrantha contained highest carbon stock in Old-growth and Riparian forests, respectively. Asymmetric mode of interaction in the absence of competition shows competition for below-ground resource, especially presence of moisture and nutrient gradient. Size inequality among different and within the same species determined coexistence tree communities in Old-growth and Riparian forests of Akure Strict Nature Reserve, respectively.