Comparative studies of biostimulation using local materials and phytoremediation in the mitigation of crude toxicity on tropical soil of the Niger-Delta of Nigeria were carried out. 5% pollution level of crude oil were done alongside the control. Remediation treatments were done after one week of pollution using the following materials: Batch A : 20g of NPK 15:15:15; batch B: 50g of poultry dung; batch C: 5 seeds of Vigna unguiculata grown on the polluted soil (phytoremediation); batch D: control (pollution but no remediation); and batch E: double control (no pollution and no remediation treatment). Soil analyses result indicated that the different remediation treatments have potentials to ameliorate crude oil toxicity at different degrees because of their ability to increase the nutrient content and decrease the total hydrocarbon content of the soil. There was no statistical difference in the soil pH, Zinc and Copper contents between and within treatments throughout the study period. Highest crude oil biodegradation and improvement in nutrient content of the soil were observed in NPK 15:15:15 and phytoremediation treatments indicating that these are good remedial treatment options in the mitigation of crude oil toxicity. @ JASEM

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SummaryThe mathematical elegance and ecological naivety problem of diversity indices is examined with special reference to the patterns of response of some current diversity indices when applied to a series of hypothetical communities with the number of species and their relative abundance pre‐determined. There is a significant positive relationship between increase in the diversity values they yield and increase in species richness. However the indices are sensitive to slight variations in the population density per species and yield grossly distorted diversity data of doubtful ecological significance. Their inappropriateness for ecological diversity studies is highlighted and an alternative ecological diversity index, Dk=S+√ 1/2 N, proposed. This index which is mathematically less cumbersome to use than many in current use, has inbuilt ecological usefulness and is unlikely to yield grossly distorted diversity values of doubtful ecological significance.RésuméOn examine l'élégance mathématique et le probléme de la naivetéécologique des indices de diversité, tout particuliérement en ce qui concerne le type de réponse de quelques indices de diversité classiques appliqués à une série de communautés hypothétiques dont le nombre d'espéces et l'abondance relative sont prédéterminées. On constate une significative relation positive entre l'augmentation des valeurs de diversité que'lles atteignent et l'augmentation de la richesse en espéces. Cependant, ces index sont sensibles aux moindres variations de densité de population des espéces et ménent á des données de diversité fort biaisées dont le signification écologique est harsardeuse.On souligne cette inadéquation pour des études de diversitéécologique et un index alternatif est proposé: Dk=S+√ 1/2 N. Cet index, qui est d'une utilisation mathématiquement moins gênante que d'autres en usage courant, s'est avéré d'une utilitéécologique qui ne produit pas des valeurs de diversité distordues et d'une signification douteuse.

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SummaryAn ecological study of the flooding tolerance of two ornamental plants–Caesalpinia pulcherrima and Crotalaria retusa–indicated that flooding had a significant adverse effect on the growth and development of the species but C. retusa was more tolerant of inundation than C. pulcherrima. Morphological development in C. retusa was reduced by 26.94% and that of C. pulcherrima by 47.11% after the plants had been subjected to 5 weeks of flooding. Metabolic activities as indicated by the amount of acids of Kreb's cycle present in root samples of control and flooded plants, were reduced by 45.71% in C. retusa, and 76.87% in C. pulcherrima, the less flooding‐tolerant species. The poor development of the affected plants is attributed mainly to the reduced level of metabolic activities brought about by inundation. The flooding tolerance assessment method used in the study was found to be sensitive and reliable and is thus considered appropriate for screening of plant species for a variety of conservation work such as river bank, flood plain and reservoir margin plantings.RésuméUne étude écologique sur la tolérance de deux plantes d'ornament–Caesalpinia pulcherrima et Crotalaria retusa‐ai l'inondation a montré un effet inverse significatif sur la croissance et le développement des espéces, C. retusaétant plus tolérante ai l'inondation que C. pulcherrima. Le développement morphologique de C. retusa est réduit de 26.9% alors que celui de C. pulcherrima l'est de 47.1% aprés 5 semaines d'immersion. Les activités métaboliques–mises en évidence par la quantité d'acides du Cycle de Krebs dans les racines des plantes expérimentales et de contrôle–ont été réduits de 45.7% chez C. retusa et de 76.9% chez C. pulcherrima, la moins résistante des deux. Le faible développement des plantes affectées est attribué principalement ai la réduction du niveau d'activité métaboliques provoquée par l'inondation. La méthode d'évaluation de tolérance á l'inondation, utilisée dans cette étude, s'est révélée sensible et fiable; on peut donc la considérer comme appropriée ai la sélection des espeices végétales pour les plantations de bordure lors d'une série de trav̀aux de conservation tels que berges de riviéres, plaines immergées et réservoirs d'eau.