Browsing by Author "Ojija, Fredrick."

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    Impacts of Alien Invasive Parthenium Hysterophorus on Flower Visitation by Insects to Co‑Flowering Plants
    (Springer, 2019-05-11) Ojija, Fredrick.; Arnold, Sarah E. J.; Treydte, Anna C.
    The exotic invasive plant Parthenium hysterophorus is invading many tropical habitats. While much work has been done on its interactions with other native plants, little is known about its interaction with insect floral visitors and how it impacts pre-existing pollination networks when it invades a site. We carried out surveys on sites with and without P. hysterophorus (invaded and uninvaded, respectively) to investigate its impact on plant–pollinator interactions with two common indicator or target plants (Ocimum gratissimum and Ageratum conyzoides) in Tanzania. During multiple 15 min observation periods in quadrats, the number of arriving flower visitors, duration of visits and visitation rate were measured and compared between sites. Visitation networks of flower visitors were developed by observing flower visitor taxonomic groups and plants visited across both invasion categories. Parthenium hysterophorus was heavily visited by a diversity of flies as taxonomic groups. Indicator plants received fewer flower visitors overall in the invaded site, implying P. hysterophorus may be disrupting pol-len flow. Foraging behavior and flower visitation by Apis mellifera and flies on target plants were particularly negatively affected in the invaded quadrats. Flower visitation rate to target plants was significantly lower in invaded quadrats than in uninvaded quadrats. This study supports work in other parts of the world demonstrating that invasive species can strongly disrupt pollination networks. By attracting flower visitors that could otherwise serve as pollinators of native plant species, P. hysterophorus which is rapidly spreading in eastern African ecosystems could have complex deleterious effects on the wider ecosystem.
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    The Role of Conservation Agriculture in Enhancing Biodiversity and Common Beans Productivity
    (Elsevier B.V, 2026) Mng’ong’o, Marco E.; Mwaipopo, Rehema E.; Ojija, Fredrick.; Matimbwa, Hadija.
    Conservation of biodiversity in agricultural landscapes is vital for maintaining ecosystem stability and resilience. Conservation agriculture, a sustainable farming approach that involves minimum tillage and reduced use of synthetic pesticides, herbicides, and growth promoters, has gained attention as a potential strategy to enhance biodiversity and reduce production costs. This study investigated the role of conservation agriculture in enhancing biodiversity and common bean productivity in Tanzania. The study compared plots practicing conservation agriculture (minimum tillage and reduced agrochemical use) with those using conventional farming methods. Biodiversity metrics, that is, earthworm populations, bird species richness, bird nest abundance, bird species diversity, bee visitation rates, and bean yield were assessed. The results showed significant positive effects of conservation agriculture on biodiversity, emphasizing its potential role in promoting sustainable agriculture, biodiversity conservation, and household improvement due to reduced production costs and increased yield per unit area. Earthworms per meter square observed to increase from 12 in the non-conservation plots to 34 in the conservation plots, which is likely to improve nutrient cycling and productivity. Furthermore, conservation plots had a higher number of bird species flying around (36− 76) compared with 14–32 in nonconservation plots (4000 m2 ) at 50 % bean flowering. The number of bird nests observed in the two plots during bean harvesting varied significantly (P