SPECIES RICHNESS, DIVERSITY, DENSITY, AND SPATIAL DISTRIBUTION OF SOIL SEED BANKS IN THE MOREMI GAME RESERVE RIPARIAN WOODLANDS OF THE OKAVANGO DELTA, NORTHERN BOTSWANA

Abstract

This study aimed to investigate the soil seed banks in the Moremi Game Reserve Riparian Woodlands (MGRWs) of the Okavango Delta, northern Botswana, from March 2019 to June 2019. We examined species richness and diversity, determined densities, assessed the spatial distribution of seeds in the soil, and compared the similarity in species composition between the standing vegetation and soil seed bank flora. A total of 124 plant species were identified in the litter and top 9 cm soil layers with a mean density of 1933 seeds m^-2. Herbs, grasses, sedges, and woody plants were represented by 69, 25, 17, and 13 species, respectively, in 33 families and 92 genera. The overall H' diversity and evenness of the soil seed bank in the MGRWs were 3.7 and 0.77, respectively. The results revealed that Poaceae, Cyperaceae and Asteraceae are the most dominant families in all the germinated species. Four plant communities, namely Kohautia virgata-Ammania baccifera, Bidens pilosa-Urochloa mosambisensis, Setaria verticillata-Brachiaria deflexa, and Cynodon dactylon-Cyperus longus were identified from the soil seed bank. Bray-Curtis ordination showed that there was an overlap between these communities in terms of seed bank composition. However, MRPP analysis showed that there was significant (P < 0.05) separation between germinated soil seed bank communities. The overall spatial horizontal distribution of seeds varied among sampling quadrats while the vertical distribution of seeds exhibited the highest densities occurring in the upper 3 cm of the soil and gradually decreasing densities with increasing depth.