Tree Structural Diversity and Yield Prediction Models for Tree Species in Old Oyo National Park, Nigeria

Adesoji Akinwumi Adeyemi,Hussainat Taiwo Taofeek

doi:10.11648/j.ajpb.20200502.11

Abstract

Evaluation of structural and species distribution is essential for conservation work. Besides, reliable baseline information is crucial for a sustainable forest management. We assessed forest structure and formulated yield-prediction models for tree species in Old Oyo National Park (OONP). Systematic sampling technique was adopted for the study. Thirty transects of 1000 m-long were laid at 1 km intervals. Four 0.25ha-plots were then alternately laid at 250 m intervals along each transect, and 120 plots were used for the study. Structural parameters including diameters at the base, breast height, middle, merchantable top and tree heights were measured for trees with Dbh ≥10 cm to compute stand density and volume. Data were analysed using descriptive statistics and regression. Species diversity and richness indices were computed using Shannon-Wiener and Margalef’s Indices. Models were assessed using R2 and standard error of estimate (SEE), overall significance of each model was evaluated using F-test. Model validation was done using t-test and bias. Sixty-four tree species in 23 families were encountered with richness and diversity indices of 1.189 and 3.544, respectively. Only one endangered (Pterocarpus erinaceus) and three vulnerable (Afzelia africana, Vitellaria paradoxa and Maranthes agnesis) species were encountered. Burkea africana was the most locally-abundant in the area with a relative density and basal area of 9.3 and 3.058 m2/ha, respectively. Fabaceae was the most-represented family. The best yield-prediction model was of the form: V=27.53 + -21.41logDB + 0.023THT² having R2, SEE and bias values of 90.5%, 0.599 and 0.005, respectively. It is recommended for future predictions.

Highlights

Forests form an integral part of life on earth, providing a range of benefits at local, national and global levels, covering approximately 30.6% of the world’s total land mass [1]
This study has shown that Oyo National Park (OONP) has moderately-high species diversity
Use-pressure impacted negatively on the local species abundance. It appeared that conservation efforts in the study area are worthwhile, much needed to be done to ensure that over-exploitations of valuable trees species are halted

Summary

Introduction

Forests form an integral part of life on earth, providing a range of benefits at local, national and global levels, covering approximately 30.6% of the world’s total land mass [1]. Forests provide a large collection of ecosystem functions and services. They produce wood for pulp and timber, and contribute to the regulation of the carbon and water cycles [6]. They host a major part of the world’s biodiversity, and provide numerous cultural services and possibilities for recreation activities [6, 7]. Several decades of biodiversity research in grasslands suggest that plant diversity is a key driver of ecosystem functioning; it enhances primary productivity and increases resistance against herbivores [6]

Methods

Results

Discussion

Conclusion