ABSTRACT

Ecological study of seasonal distribution of weeds in oil palm plantation at Agbarha-Otor, Ughelli North Local Government Area of Delta State, Nigeria, was carried out during the rainy and dry seasons of 2020. Quadrats measuring 10 m² were laid at random and information on the weed species were gathered and used to generate diversity indices as well as other ecological statistics. During the dry season the taxa ranged from 27 - 50, individual abundance (376 – 2821), Dominance_D (0.1819 – 0.4248), Simpson index (0.5752 – 0.962), Shannon Wiener idex (1.469 – 3.468), Evenness index (0.132 - 0.7635), Brillouin (1.437 – 3.268), Menhinick index (0.7073 – 2.116), Margalef index (3.569 – 6.914), Equitability (0.4301 – 0.9278), Fisher_alpha (4.705 – 8.632), Berger-Parker (0.07979 – 0.6424) and Chao-1 was (27.38 – 50.5). In terms of most abundant species, density, relative density and importance index value in dry season in decreasing order were Poaceae > Selaginellaceae > Arecaceae > Melastomataceae > Bromeliaceae > Asteraceae. Diverse families in decreasing order were Poaceae > Asteraceae > Fabaceae = Rubiaceae = Malvaceae > Amaranthaceae = Connaraceae > Acanthaceae =Cyperaceae = Euphorbiaceae = Polypodiaceae = Tiliaceae = Gentianaceae with 7, 6, 5, 5, 5, 3, 3, 2, 2, 2, 2, 2 and 2 species respectively. While in the rainy season taxa ranged from 32 - 57, individuals (312 – 2178), Dominance, Simpson, Shannon Weiner, Evenness, Brillouin, Menhinick, Margalef and Equitability indices were (0.04491 – 0.4904; 0.5096 – 0.9551; 1.488 – 3.454; 0.10390 – 586; 1.426 – 3.284; 0.7037 – 2.887; 4.061 – 8.706) respectively. Equitability (0.4182 – 0.866), Fisher_alpha (5.373 – 17.31), Berger-Parker (0.1197 – 0.6944) and Chao-1 were (32 – 62.08) respectively. In terms of most abundant species, density, relative density and abstractimportance value index in rainy season, six weed families namely Poaceae, Asteraceae, Fabaceae, Malvaceae, Rubiaceae and Connaraceae were predominant. Similarly, the most diverse families in decreasing order were Poaceae > Asteraceae, = Fabaceae, > Rubiaceae, = Malvacee, > Connaraceae = Amaranthaceae, > Acanthaceae = Cyperaceae = Euphorbiaceae = Gentianaceae = Polypodiaceae = Tiliaceae with 7, 6, 6, 5, 5, 3, 3, 2, 2, 2, 2, 2 and 2 species respectively.The knowledge of weed flora will enable us to know the appropriate method to eliminate them from our agricultural farms to reduce competition with our valuable crops.