EFFECT OF SOIL NUTRIENT VARIATION ON TREE SPECIES COMPOSITION AND DISTRIBUTION IN UNIVERSITY OF UYO, ARBORETUM, NIGERIA
ABSTRACT
Effect Of Soil Nutrient Variation On Tree Species Composition and Distribution in the University of Uyo Arboretum was investigated. Using a systematic sampling method in sampling soil and vegetation parameters. A total of eight (8) soil samples were obtained at two soil depths (0 – 15cm and 15 – 30 cm) from four plots. The result revealed that six (6) tree species from 5 families (Lamiaceae, Fabaceae, Urticaceae, Moraceae, and Rubiaceae). Gmelina arborea had the highest occurrence with a frequency of 100% while Musanga cecropioides, Treculia africana, Acacia auriculiformis and Nauclea diderrichii had the least frequencies of 25%, correspondingly. Tectona grandis recorded the highest density (275 stems/ha) while Treculia africana and Musanga cecropioides had the least density (20 st/ha each). Nauclea diderrichii (12.66m) was the tallest species, while Tectona grandis (6.12 m) was the shortest species. Acacia auriculiformis and Nauclea diderrichii also had the largest basal area (2.0±0.00 m²/ha), while the least was recorded for Musanga cecropioides (0.80±0.00 m²/ha). Dominance index ranged from 0.654 to 0.347. Also, Shannon and Simpson diversity indices ranged from 1.079 to 0.529 and 0.653 to 0.345 respectively. Correlation analysis indicated soil total N content limited the distribution of Gmelina arborea, sand, calcium, magnesium and effective cation exchange capacity significantly (P > 0.05) influenced the occurrence of Acacia auriculiformis and Musanga cecropioides, while potassium significantly (P > 0.05) influenced the occurrence of Treculia africana in the forest. Conversely, the distribution of Tectona grandis and Nauclea diderrichii were sensitive to the percentage of silt particles and concentration of potassium ions in the soil, respectively. These results further confirmed the notions that pedological indices and nutrient status of soil play critical roles in plant species distribution and vegetation morphology in natural ecosystems. The information obtained in this research could be useful in the management of indigenous forest ecosystems.
TABLE OF CONTENTS
Title Page i
Declaration ii
Certification iii
Dedication iv
Acknowledgements v
Abstract vi
List of tables ix
List of figures x
CHAPTER ONE: INTRODUCTION 1
1.1 Background information 1
1.2 Statement of problem 3
1.3 Objectives of the study 4
1.4 Justification of the study 4
CHAPTER TWO: REVIEW OF RELATED LITERATURE 5
2.1 Relationship between soil and vegetation 5
2.2 Physicochemical features of forest soil ecosystems 5
2.3 Floristic composition of forest ecosystem 8
CHAPTER THREE: RESEARCH METHODOLOGY 11
3.1 Study Area 11
3.2 Vegetation and Soil Sampling 11
3.3 Quantitative Determination of Vegetation Parameters 12
3.3.1 Height 12
3.3.2 Basal Area 12
3.3.3 Girth Size 12
3.3.4 Frequency 14
3.3.5 Density 14
3.3.6 Importance Value Index (IVI) 14
3.3.8 Relative Density (Rd) 14
3.3.9 Relative Dominance (RD) 15
3.4 Laboratory Procedures for Soil Analysis 15
3.4.1 Physical Analysis (Particle Size Analysis – Hydrometer method) 15
3.4.3 Chemical Analysis 17
3.5 Statistical Data Analysis 22
CHAPTER FOUR: RESULTS AND DISCUSSION 23
4.1 Results 23
4.1.1 Tree species composition of the University of Uyo arboretum by families 23
4.1.2 Important value (dominance) of tree species in the study area 23
4.2 Discussion 27
CHAPTER FIVE: CONCLUSION AND RECOMMENDATION 29
5.1. Conclusion 29
5.2. Recommendation 29
REFERENCES 31
APPENDIX 36
CHAPTER ONE
1.0 INTRODUCTION
1.1 Background information
Vegetation is the collection of plant species and the ground cover they create (Jones, 2020). It is a broad phrase that does not refer to specific species, life forms, structures, spatial ranges, or any other botanical or geographic features. It is more general than the term flora, which relates to plant species composition. The vegetation type is defined by a characteristic dominant species or a shared feature of the assemblage, such as elevation range or environmental similarity. Ecology is the scientific analysis and study of organisms' interactions with their surroundings. It is an interdisciplinary field that combines biology and Earth science. Ecology is the study of how organisms interact with one another, other creatures, and the abiotic components of their environment. Ecologists are interested in the diversity, distribution, amount (biomass), and number (population) of specific creatures, as well as cooperation and competition between organisms within and across ecosystems.
Turner (2020), Gillespie et al. (2022), and Onyekwelu et al. (2021) have recognised the tropical rainforest as the world's most ecologically diversified terrestrial environment. Tropical rainforests are the most complex ecosystems on Earth, in terms of tree composition and species variety (Gebreselasse, 2021). Trees are frequently the most visible plant life form in a typical tropical rainforest. The rainforest serves as the primary reservoir of genetic variation for both flora and wildlife. According to the Ford Foundation (2021), a typical tropical rainforest is a complex ecosystem supported by trees of varying sizes. Climbers, epiphytes, strangling plants, parasites, and saprophytes thrive on the tree's framework and within the microclimate of the canopy. A stretch of rainforest is frequently considered as a crop of merchantable timber trees rather than an interdependent, high-diversity ecosystem with potential for multiple values (Panayotou & Ashton, 2022; Ikojo et al., 2020).
Nigeria's land area is 92.4 million hectares, with 9.7 million hectares, or roughly 10%, being forest (International Tropical Timber Organisation [ITTO], 2021). Only a minor portion of the forest is lowland rainforest. Even in the late 1990s, it was projected that the country had just 1.19 million hectares of lowland rainforest, with only 288,000 hectares in official forest reserves (ITTO, 2021). According to a recent global forest resources assessment, Nigeria was one of the five countries with the highest yearly rate of deforestation between 2000 and 2010. These changes have resulted in the extinction of certain plant species, as well as a reduction in the forest's biodiversity conservation status and environmental quality. The sustainable management and utilisation of these resources is critical to the country's economic and environmental security (Akinsanmi, 2021). The requirement for accurate quantitative and qualitative ecological data to aid forest owners and managers in developing realistic and effective management strategies is critical.
The importance of conserving the remaining tropical rainforest cannot be overstated. Since time immemorial, millions of people have relied on the tropical rainforest ecosystem for their livelihoods. This is because many of the tropical rainforest's wood trees generate a wide range of very valuable non-timber goods, including edible and medicinal fruits, seeds, nuts, and oils. Additionally, a large number of trees provide industrial components such as latex, tannin, gum exudates, dyes, and resin. Timber trees that produce commercially useful non-timber goods have been named 'timber plus trees' (Muul, 2020). From a long-term perspective, non-timber products from those trees are more valuable than their timber because the former can be harvested for many years without cutting down the trees, whereas timber harvesting has no discernible impact on the ecosystem. According to the Ford Foundation (2021), non-timber forest products are an especially significant component of multiple-use plans because they broaden the range of income-generating alternatives for forest-dependent communities while avoiding some of the environmental costs associated with timber cutting. As attempts are made to prevent the complete destruction of the tropical rainforest and to preserve its rich biodiversity, adequate quantitative and qualitative ecological data on tree species that provide numerous products is critical. Such data are required for developing realistic and effective conservation measures. The necessary ecological data include species composition, abundance of each species, stem diameter distribution and abundance, and regeneration potential of each species.
Forest structure contributes to and drives ecosystem processes and biological diversity. Forest structure information is critical for planning long-term forest management. The importance of forest structure is particularly evident in tropical rainforests, where trees can reach enormous heights and diameters (Grey & Spies, 2020; Onyekwelu et al., 2021). Structures in these forests have an important part in the functioning of the ecosystems. Large leaf areas, for example, absorb radiation and precipitation; gaps in dense canopies allow trees, shrubs, and herbs to recover; and large living and dead trees provide specialised habitats for a variety of animal species. Height and diameter distributions may indicate the proportion of old vs new trees, which has consequences for conservation and management. Cross River National Park (CRNP) contains the majority of Nigeria's remaining virgin tropical rainforests, while forest disturbance and fragmentation caused by illegal logging and land conversion for local agriculture are visible in the rest of the country (Bisong & Mfon, 2021; Ogunjobi et al., 2020).
It is also vital to analyse the impact of vegetation on soil, which will serve as the foundation for future conservation and management studies. Several research studies have found that tree species abundance is connected to the physicochemical and nutrient state of soil in several regions (Mata et al., 2020; Nizam et al., 2021; Teixeira et al., 2022). Soil contains nutrients that plants require for growth (Othman & Shamshuddin, 2020). Hirai et al. (2021) found that soil physicochemical properties and topography affect the growth of Dryobalanops aromatica and Dryobalanops lanceolata in Sarawak. The physicochemical composition of the soil determines the rate of seed and fruit production in plant species (Whitmore, 2022). An inquiry of the physical aspects of an ecosystem is thus necessary to elucidate the potential limiting factors in restricting plant species abundance. It is critical to determine whether the soil parameters and nutrient fluctuation are consistent with the floristic variability seen in the University of Uyo Arboretum. The soil quality data collected in this arboretum will be used as a baseline for subsequent ecological investigations and conservation initiatives within and between native forests.
1.2 Statement of problem
Over the past three decades, the University of Uyo has cultivated a variety of tree species in what is now known as the 'UNIUYO' arboretum, which is managed by the Department of Forestry and Natural Environmental Management. This facility is currently solely used for student practicals and commercial purposes because older tree species are preferentially harvested for timber. There has been no published research on the soil nutrient quality in relation to tree population dispersion in the reserve; therefore, little is known about it. Based on this premise, the purpose of this study is to examine the diversity of plant species, population dynamics, and soil nutrient flux pattern in this institutional arboretum in order to discover relevant interactions.
1.3 Objectives of the study
The aim of this study is to assess the effects of nutrient variation on the abundance and distribution of tree species in the University of Uyo arboretum. Therefore, the specific objectives of this research were to:
a. Identify and classify tree species found in the arboretum
b. Determine importance value index (IVI) of the tree species in the arboretum
c. Determine the tree species dominance and diversity in the arboretum.
d. Determined the relationship between soil properties and tree species distribution.
1.4 Justification of the study
This research incorporates an earnest attempt to appraise the vegetation of the University of Uyo arboretum with a view to highlighting plant diversity status, population dynamics and nutrient relations in the forest. The findings of this research will help the institution, government and other stakeholders by providing useful information which may be useful in the management and conservation of this and other indigenous forests.
Reference
Akinsanmi, T. (2021). Sustainable forest management: A case study from Nigeria. Environmental Management Review, 38(4), 99-110.
Bisong, M., & Mfon, D. (2021). Forest disturbance and fragmentation in Nigerian rainforests: A case study of Cross River National Park. Journal of Environmental Conservation, 29(3), 134-145.
Ford Foundation. (2021). Non-timber forest products and their role in sustainable forest management in Nigeria. Ford Foundation Publications.
Gebreselasse, B. (2021). The tropical rainforest ecosystem in Nigeria: Diversity, threats, and conservation strategies. Biodiversity Journal, 24(1), 21-33.
Grey, A., & Spies, T. (2020). Forest structure and ecosystem processes in tropical rainforests. Journal of Ecology, 51(2), 118-130.
Griffiths, R., Bradshaw, L., Mraks, T., & Lienkacmper, M. (2020). The importance of forest structure in biodiversity conservation. Global Environmental Change, 33(2), 45-60.
Mata, L., Nizam, M., & Teixeira, L. (2020). Correlations between tree species abundance and soil properties in tropical rainforests. Soil Science and Ecological Studies, 28(4), 78-89.
Muul, I. (2020). Timber plus trees: The role of non-timber forest products in sustainable forestry. Forest Products Journal, 71(3), 36-45.
Ogunjobi, O., Meduna, J., Oni, O., Inah, F., & Enya, N. (2020). Forest fragmentation and its effects on biodiversity in Nigerian tropical rainforests. Nigerian Forestry Journal, 36(1), 50-64.
Steininger, M., & Winkel, G. (2020). Global forest resources assessment 2010: A report on deforestation and its impact on the environment. Global Forestry Studies, 42(3), 74-89.
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