Comparative Study of Soil Bacteria from the Rhizosphere of Two Selected Tree Species (Anogeissus leiocarpa and Pterocarpus erinaceus) in Shere Hills, Plateau State, Nigeria

The comparative study of soil bacteria from the rhizosphere was carried out using samples obtained from the soil (rhizospheres) of Anogeissus leiocarpa and Pterocarpus erinaceus using purposive sampling method. The soil samples were collected at a depth of 0-30cm and 30-60cm around the rhizosphere of the studied tree species and away from the rhizosphere used as a control. The method by Ibitoye (2008) was used to test for physico-chemical properties and method by Cheesborough (2006) was used for stocking, culturing, incubating and gram staining. Result for the mean physical properties shows, P. erinaceus had highest mean values for clay and silt which wasn’t significant (p= 0.067 and 0.381 respectively). A. leiocarpus had the second highest clay and silt. Sand and bulk density was highest for the control which was highly significant (p = 0.000 and p=0.044 respectively). For mean chemical properties among plant species, pH, EC, OC, OM, N, Na, Ca and CEC were highly significant (p<0.05), while p, K, Mg and EA were not significant. Pterocarpus erinaceus had the highest mean for all the chemical elements assessed with ten (10) bacteria species identified. Anoigessus leiocarpa had the second highest biochemical elements present with six (6) species of bacteria identified, Bascillus subtilis was most common. It is therefore necessary that these tree species are allowed in their natural habitat to preserve and conserve these microbes in the ecosystem.

Effect of nursery substrate on the growth of Pterocarpus erinaceus Poir. seedlings

The high pressures on Pterocarpus erinaceus Poir. severely affect its natural stands in West Africa. The measures taken to reverse this trend are still inefficient due to plantlets production constraints. This study aims to understand the importance of growing substrates on seedlings growth in nursery. Composite soil samples were collected at 20 cm depth from 4 seed trees in 5 different sites in Togo (West Africa). Two batches were made for each site, one of which was sterilized by autoclave and the other has received no treatment. Three growing parameters (length of stem, number of buds and number of leaves) of the plantlets obtained from sterilized seeds were measured during 20 weeks in the nursery. Results show for each site a significantly better growing rate of seedlings on unsterilized substrates, compared to sterilized substrates. At the end of the experiment, plantlets were 8.75 ± 2.32 cm mean height on sterilized substrates when they reach 19.20 ± 5.00 cm on unsterilized substrates. The mean number of buds and leaves per plantlet varies from 2.23 ± 1.71 buds and 3.00 ± 1.86 leaves to 10.73 ± 3.28 buds and 11.09 ± 2.48 leaves at the same date, respectively on sterilized and unsterilized substrates. The low growing rate on sterilized substrates should be linked to the low capacity of plantlets in mobilizing phosphorus, potassium and nitrogen without microorganisms. Negative impacts of sterilization were highlighted on seedlings by necrosis of buds and leaves from the 7th week of growth, demonstrating a positive effect of soil microorganisms on the proper development of the seedlings.

Mycorrhizal Status of Natural Stands of Pterocarpus erinaceus Poir. (Fabaceae) in Sudanian and Guinean Zones of West Africa

Background and Aims: The sylviculture of Pterocarpus erinaceus is still in its infancy due to lack of information on its biology. The aim of this study is to investigate its mycorrhizal status in order to better address its sylviculture. Place and Duration of Study: The study was performed on the field from May 2019 to December 2020 and data were analyzed at the laboratory from January to March 2021. Methodology: The frequency and intensity of mycorrhization were determined under a microscope after staining with trypan blue of fine roots collected at a depth of 20 cm under adult plants at 5 sites, 3 in the Guinean zone and 2 in the Sudanian zone in Togo. The spore density was obtained on soil samples taken at the same depth under the same trees. Results: Results indicate, without significant differences (P value = 0.166) among sites, and show that P. erinaceus is frequently mycorrhized (88% to 94%). However, there were significant differences (P value = 0.001) in spore densities between sites located in the Sudanian zone (16.53 ± 1.25 and 10.66 ± 0.71 spores per gram of soil – SPGS – respectively for the Fazao-Malfakassa and Oti-Kéran-Mandouri) and those located in the Guinean zone (4.54 ± 0.3, 2.93 ± 0.43 and 3.76 ± 1.01 SPGS respectively at Abdoulaye, Hahomegbe and Togodo). There are significant differences between mycorrhization intensities Togodo which has a mycorhization intensity of 33.52 ± 2.54 and other sites. The redundancy analysis carried out by taking into account substrates’ chemical characteristics shows that spore density remains low when phosphorus and nitrogen are important in the rhizosphere whereas the intensity of mycorhizations is low when PHKCl is high. Conclusion: This study provided evidence of mycorrhizal symbiosis in Pterocarpus erinaceus whether in the Sudanian or Guinean zone. Chemical quality of the growing substrate has an influence on parameters of mychorization. Further studies should therefore allow an assessment of the degree of dependence of this species with respect to the possible benefits associated with this symbiosis.

Vingt-deux espèces d’arbres autochtones plantées en arboretum à Korhogo au nord de la Côte d’Ivoire : trois décennies de suivi

En Afrique tropicale, dans les plantations forestières, la majorité des espèces autochtones ont été délaissées au profit d’espèces exotiques à croissance initiale rapide. Cette tendance est encore plus marquée dans les zones soudanienne et soudano-guinéenne à longue saison sèche. Ainsi s’explique le manque de connaissances sur les potentialités et la sylviculture des espèces d’arbres autochtones ou « locales ». Pour contribuer à l’acquisition de ces connaissances indispensables, un arboretum de 2,56 ha a été installé en 1990 à proximité de Korhogo dans le nord de la Côte d’Ivoire. Sa particularité réside dans la mise en place de grandes parcelles de 1 596 m² avec 224 plants par espèce afin d’y mener une sylviculture qui conserverait de 10 à 16 arbres adultes de chaque espèce, exploitables notamment pour le bois d’œuvre, au terme de la révolution. Par manque de maîtrise des techniques de pépinière pour certaines espèces, seules 12 espèces sur 22 ont été plantées avec les 224 plants prévus au départ. Les résultats sont présentés pour l’ensemble des espèces testées, aussi bien en pépinière qu’en plantation. Cet arboretum a été régulièrement suivi jusqu’en 1999 puis ne l’a plus été en raison des évènements politiques qui ont perturbé la bonne administration du pays. Une campagne de mesures a été diligentée en novembre 2019 qui a permis notamment de tirer des conclusions intéressantes sur l’aptitude de 15 espèces à croître en peuplements équiennes monospécifiques, dont deux (Pterocarpus erinaceus Poir. et Anogeissus leiocarpa (DC.) Guill. & Perr.) qui montrent une productivité remarquable. L’ensemble des données recueillies depuis la récolte des graines et tout au long de la vie de l’arboretum sont présentées ici et discutées dans l’espoir que les sylviculteurs de cette zone phytogéographique en tirent le meilleur profit. Les enseignements acquis doivent servir à la restauration des forêts et des paysages grâce aux reboisements auxquels les États se sont engagés pour lutter contre les variations climatiques, la perte de biodiversité et la dégradation des services écosystémiques aux populations.