The genus Khaya is extractives rich, but the extractives in the stem bark are among the most abundant, accessible and utilised materials in Nigeria. These extractives are of considerable interest for wood protection because of their pesticidal properties. In this study, the chemical constituents of Khaya ivorensis stem bark and their termiticidal activity were investigated on Triplochiton scleroxylon and Vitex doniana woods. Spectrophoto-metric and Forlin-Ciocalteu analyses showed that Khaya ivorensis stem bark contained total: alkaloids 38,98±0,02 mg/g, flavonoids 0,37±0,02 mg/g, phenol 50,62±0,11 mg/g, saponins 156,31±0,76 mg/g, and tannins 59,95±0,54 mg/g. Field tests demonstrated that the extract from Khaya ivorensis stem bark had significant termiticidal activity at tested concentrations compared to the control. The results indicated that Khaya ivorensis stem bark has potential as a natural agent for termite control.

Trees are a central component of most urban communities, providing diverse benefits such as improving air quality, increasing aesthetic appeal, preventing erosion and providing habitat for wildlife. However, there is inadequate information on the distribution and diversity of these trees within our academic environments. This study investigates the distribution, frequency and species diversity of amenity trees within the main campuses of tertiary institutions in River State, Nigeria. The selected tertiary institutions are University of Port-Harcourt (Institution A) and Rivers State University (Institution B). Five (5) major roads in each campus were randomly selected, and 200m along each road was selected as sample areas. Ten (10) meter was marked from the edge of the road, and complete inventory was taken of all trees within the marked sample area. Diameter at breast height (DBH), crown diameter and tree height were measured. Shannon-Weiner and Simpson diversity index were used to calculate amenity trees diversity, while Margalef specie richness was used to calculate the species index. A total of 539 trees were surveyed on both campuses, comprising 26 different species and 10 families. Casuarina equisetifolia had the highest frequency with 92 trees in B. Simpson diversity index showed higher diversity (D = 0.78) in B amenity trees than A (D = 0.81). Shannon-Weiner species evenness was 0.71 and 0.76 for Institutions A and B respectively. Margalef specie richness index were 2.90 for A and 1.40 for B. This study provides baseline information for ecosystem management of urban forest tree species within campuses. For sustainable management of trees on campuses, frequent inventory and survey should be conducted to establish their abundance, distribution and diversity.

The process of urbanization causes alterations in the landscape, affects the environment negatively and the community is placed at risk. In an attempt to sustain urban growth, urban areas have now developed their own urban climate which alters thermal conditions. As the process of urbanization continues to increase in the face of climate change, these problems are likely to be exacerbated. There is a need to find ways to reduce these negative effects. Hence this study aimed to evaluate the effect of five ornamental tree species on temperature reduction in University of Port Harcourt. Five ornamental tree species effectiveness on temperature reduction were comparatively evaluated. Thirty trees in each species were randomly selected and diameter measurements at various points were taken on the selected trees. Temperature readings were taken both under the tree species and on bare ground where there were no planted trees. There was significant difference between temperature under tree and that in bare ground. From the result it was observed that the average temperature reduction due to the presence of trees ranged between 0.64oc to 2.03oc. The species were also significantly different in its effectiveness to reduce temperature. Magnifera indica had the highest effectiveness in temperature reduction of 2.03oc. The result shows that crown diameter and crown projection area influence the amount of temperature a species can effectively reduce. Conclusively, the results suggest that ornamental trees provide environmental benefits in urban area, and these benefits are strongly dependent on the species and planting conditions.Keywords: Crown, Climate change, Shading, Temperature, Urban environment

This study was conducted in 2019 to compare the growth performance and soil quality of two agesequences of Gmelina arborea plantation within the premises of the University of Port Harcourt, Nigeria. Data were collected from two stands of G. arborea established in 2011 and 2015. Growth performance was evaluated based on tree growth variables and above-ground carbon stored. Tree growth variables estimated were total height (TH), diameter at breast height (DBH), crown height (CH), crown diameter (CD) and merchantable height (MH). Topsoil (0 – 30 cm) samples collected from the two sites were analyzed for particle size distribution, organic carbon (OC), total nitrogen (TN), available phosphorus (Av.P), exchangeable bases (Mg, Ca, K and Na), exchangeable acidity (Al+ H+), effective cation exchange capacity (ECEC), base saturation (BS), pH, Manganese (Mn), Iron (Fe), Copper (Cu) and Zinc (Zn). The above-ground biomass (AGB) and carbon stock (CS) were also determined. T-test was used to test for significant difference in the measured parameters between the two age-sequences of G. arborea. Higher values for TH, DBH, CS and MH were recorded for the older stand although the differences between the two age-sequences were not significantly different (p ≥ 0.05). The AGB and CS per hectare were higher for the older than the younger G. arborea stand (302.27 m3 ha-1 and 151.52 m3 ha-1, respectively). Higher values for silt, clay, Ca, Mg, Al+ H+, ECEC, BS, Mn, Fe and Zn were also recorded for the older stand. However, the observed differences were only significant (p < 0.05) for clay, pH, Av.P, Mn and Fe. The study revealed that although soil properties, tree growth as well as carbon sequestration capacity of G. arborea stand improved/increased with age, the differences were mainly not statistically significant (p ≥ 0.05) between the two (eight and four years) age-sequences. Keywords: Gmelina arborea, age sequence, soil quality, carbon sequestration