Article

Assessment of species diversity and distribution of woody species on selected plots in Olokemeji Forest Reserve, Ogun State, Nigeria

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Abstract

The Assessment of forest species composition and species diversity is essential in understanding the status of tree population and diversity for conservation purpose. Olokemeji forest reserve is situated in the lowland rain forest of south-western Nigeria and it occupies a total land area of 58.88 km2 . Six study plots of 50m2 each were randomly selected and designated as Frequently Burnt Plot 1, Frequently Burnt Plot 2, Harvested Plot, Unharvested Unburnt Plot, Arable Plot 1 and Arable Plot 2 for the purpose of assessment of species diversity and distribution of woody species. Seven species of trees were identified belonging to five families. One hundred and eighty two stands were enumerated, with Unharvested Unburnt Plot having the highest number of trees at 50. The dominance index for the woody flora was 1 in Frequently Burnt Plot 1 and 2 as well as Arable Plot 1 and 2 except for the Harvested Plot that had the lowest (0.29) while the Unharvested Unburnt Plot had 0.75. Highest species richness was recorded at the Harvested Plot at 0.71. The species diversity in Harvested Plot was low (1.54), while it was extremely low in Unharvested Unburnt Plot (0.43). Evenness index was lowest in the Unharvested Unburnt Plot at 0.43. Tectona grandis had the highest relative importance value in the Frequently Burnt Plot 1. The low species richness and species diversity is a direct indication of anthropogenic interference in the study plots and the forest reserve; this requires urgent mitigation to prevent a total loss of its structure and function as expected of a forest reserve. Keywords: Species, Diversity, Evenness, Anthropogenic, Forest, Dynamics

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... It has been pointed out that an understanding of the tree composition and structure of a forest is crucial for evaluating the economic viability of the ecosystem, species preservation, and ecosystem management (Kacholi, 2014). Studies have established that human intervention, such as logging and land conversion, can lead to low species richness and diversity in a forest ecosystem (Taiwo et al., 2020). ...
... This study also maintained that there are differences in species richness among woody plant species, which may be due to favourable environmental conditions, less competition for space, and the adaptability of species (Bello et al., 2013). The low species diversity in disturbed plots may be a result of high levels of anthropogenic interference, indicating the need for urgent intervention to protect the structure and function of the forest reserve (Taiwo et al., 2020). Additionally, the higher stem density in undisturbed plots compared to disturbed plots can be attributed to the level of human disturbance, with disturbed plots experiencing a more pronounced impact due to their lower level of protection within the forest reserve (Bentsi-Enchill et al., 2022). ...
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... It has been pointed out that an understanding of the tree composition and structure of a forest is crucial for evaluating the economic viability of the ecosystem, species preservation, and ecosystem management (Kacholi, 2014). Studies have established that human intervention, such as logging and land conversion, can lead to low species richness and diversity in a forest ecosystem (Taiwo et al., 2020). ...
... This study also maintained that there are differences in species richness among woody plant species, which may be due to favourable environmental conditions, less competition for space, and the adaptability of species (Bello et al., 2013). The low species diversity in disturbed plots may be a result of high levels of anthropogenic interference, indicating the need for urgent intervention to protect the structure and function of the forest reserve (Taiwo et al., 2020). Additionally, the higher stem density in undisturbed plots compared to disturbed plots can be attributed to the level of human disturbance, with disturbed plots experiencing a more pronounced impact due to their lower level of protection within the forest reserve (Bentsi-Enchill et al., 2022). ...
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... It has been pointed out that an understanding of the tree composition and structure of a forest is crucial for evaluating the economic viability of the ecosystem, species preservation, and ecosystem management (Kacholi, 2014). Studies have established that human intervention, such as logging and land conversion, can lead to low species richness and diversity in a forest ecosystem (Taiwo et al., 2020). ...
... This study also maintained that there are differences in species richness among woody plant species, which may be due to favourable environmental conditions, less competition for space, and the adaptability of species (Bello et al., 2013). The low species diversity in disturbed plots may be a result of high levels of anthropogenic interference, indicating the need for urgent intervention to protect the structure and function of the forest reserve (Taiwo et al., 2020). Additionally, the higher stem density in undisturbed plots compared to disturbed plots can be attributed to the level of human disturbance, with disturbed plots experiencing a more pronounced impact due to their lower level of protection within the forest reserve (Bentsi-Enchill et al., 2022). ...
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... In contrast, the very low diversity values observed in other plots can be attributed to the dominance of large native trees, which limit the establishment and growth of other species in the region. Meanwhile, evenness values across plots may indicate an imbalance in the distribution of species abundances, with some species being much more abundant than others (Taiwo et al. 2021). Moreover, plots with higher proportions of IAPS exhibited lower diversity and evenness, indicating potential disruption to ecosystem stability . ...
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The influence of selective logging on natural regeneration of woody species at logged areas in Harenna forest, southeast Ethiopia was investigated. The survey was done systematically at three different logged areas within the forest having variable size and age. Felling gaps at each over-logged area were enumerated to assess logging intensity. At every 5 m interval on each transect, quadrats of 2 m X 2 m (4 m 2) were laid for seedling regeneration survey, while for saplings and trees the size of quadrats was increased to 20 m x 20 m (400 m 2). All regenerated woody species found in each quadrat were identified, height and diameter measured and recorded. Composition, density and diversity of regenerated species were found variable among the over-logged areas. Eleven tree species were found regenerated in all the three over logged areas. Overall, mean densities of natural regeneration on logged fields varied between 267-273 individuals/ha for trees, 133-1409 individuals/ha for seedlings, and 35 individuals/ha for saplings. Logging intensities ranged between 18 and 48 trees per hectare. Species richness and diversity also varied between logged areas. Croton macrostachyus showed higher probabilities of felling gaps replacement. The change in composition from Podocarpus falcatus forest to Croton macrostachyus forest at logged fields will become a problem for sustained timber production in the area. Thus, application of silvicultural treatments that foster regeneration of desirable species at logged fields, and reducing the intensity of selective removal of Podocarpus falcatus for timber are among the recommended management options to protect and conserve the Harenna forest.
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"Measuring Biological Diversity assumes no specialist mathematical knowledge and includes worked examples and links to web-based software. It will be essential reading for all students, researchers, and managers who need to measure biological diversity."--BOOK JACKET.
Article
Afromontane rainforest stands in Ethiopia with a high frequency of wild populations of Coffea arabica are commonly known as ‘coffee forests’. These forests are important for the conservation of the genetic diversity of wild Arabica coffee, and for subsistence coffee production. This study analyses the floristic composition and environmental factors of such coffee forests, using the Yayu forest as a case. Fifty-eight plots of 20 m × 20 m were assessed, and a total of 220 plant species, representing 73 families, were recorded, of which 71 were trees, 28 shrubs, 27 climbers and 94 herbs. A cluster analysis, coupled with indicator species analysis, revealed three plant community types, which can designated as C. arabica–Cassipourea malosana, Argomuellera macrophylla–Celtis africana and Dracaena fragrans–Teclea noblis communities. The C. arabica–C. malosana and D. fragrans–T. noblis communities occur at relatively higher altitudes (1450 and 1435 m on average) on gentle and steep slopes, respectively, while the A. macrophylla–C. africana community occurs on steep slopes at lower altitudes (1380 m on average). C. arabica is one of the most frequent species in the Yayu forest, and its abundance is strongly negatively correlated with slope. These habitat differences, together with the predominance of Coffea in the understorey, support the floristic circumscription of a coffee forest. Forests commonly known as “coffee forests” have, therefore, to be viewed as a complex mosaic of different plant communities, which needs to be taken into consideration in the designation of conservation areas and differential management planning.The plant species composition of Yayu forest is predominantly Afromontane rainforest type, with several dry peripheral semi-deciduous Guineo-Congolian forest type species. Hence, Yayu forest can best be described as transitional between these lowland and montane forest types.
Article
Two different biodiversity indicators based on tree species diversity are being used, in Europe and France respectively, without strong prior scientific validation: (1) tree species or genus richness as a positive indicator, and (2) relative abundance of the main species (“dominance”) as a negative indicator. We tested the relevance of these ecological models as indicators of understory vegetation biodiversity by comparing them to other ecological models, mainly related to tree species composition and abundance. We developed Bayesian statistical models for richness and abundance of ecological groups of understory vegetation species, classified according to successional status or shade tolerance. The count data probability distributions in the models were new to ecology. These models were fitted using data from 49 plots in mature lowland forests in the center of France (Bassin Parisien) with similar site conditions. We used equivalence and inequivalence tests to detect negligible and non-negligible effects.
Effects of prescribed burning on bacterial and fungal communities of top soil in Olokemeji Forest Reserve
  • A Akinsoji
  • E Sowemimo
Akinsoji, A. and Sowemimo, E. 2005. Effects of prescribed burning on bacterial and fungal communities of top soil in Olokemeji Forest Reserve, Nigeria. The Ekologia, 3(2): 13-19.
Paleontological statistics version 2.08. Natural History Museum
  • O Hammer
Hammer, O. 2011. Paleontological statistics version 2.08. Natural History Museum, University of Oslo. 210pp.
The Olokemeji Forest Reserve II. The local history of the reserve
  • S B Hopkins
Hopkins, S. B. 1972. The Olokemeji Forest Reserve II. The local history of the reserve, The Nigerian Field, 34: 171.
  • J Hutchinson
  • J M Dalziel
Hutchinson J. and Dalziel J. M., 1954. Flora of nd West Tropical Africa, vol. 1, 2 ed. Crown Agents for Overseas, London, pp. 264-281
Pattern of plant species diversity in a dry forest ecosystem of Nigeria
  • Oluwatosin
  • S O Jimoh
Oluwatosin, B and Jimoh, S. O. 2016. Pattern of plant species diversity in a dry forest ecosystem of Nigeria, Journal of Forestry Research and Management, 13: 31-47.
Status and prospects of Forest policy in Ethiopia
  • Y Yonas
Yonas, Y. 2001. Status and prospects of Forest policy in Ethiopia. In: Imperative problems associated with forestry in Ethiopia. Workshop Proceedings, Biological Society of Ethiopia, Addis Ababa, pp. 9-30.