Soil seed bank dynamics of two invasive alien plants in Nigeria: implications for ecosystem restoration.

The assessment of seed banks could provide useful hints towards ensuring restoration planning and invasive species management. In this study, the impacts of two invaders such as Hyptis suaveolens and Urena lobata on the soil seed banks were investigated. We also assessed the seed characteristics of the invaders at the invaded sites. This was achieved using 10 sites each for H. suaveolens- and U. lobata-invaded habitats and -non-invaded habitats making a total of 30 sites. We collected 200 soil samples from each habitat type. A seedling emergence method was used to determine the seed bank recruitment of both invasive plants. The diversity indices of the above-ground vegetation of sites invaded by the two plants were significantly lower than those of the non-invaded sites. Only two plant species emerged from the seed banks of H. suaveolens and five plants from those of U. lobata when compared with non-invaded sites where 53 species emerged. A larger portion of the seeds was located in the soil's lower layer at all the sites invaded by H. suaveolens while those of U. lobata and non-invaded sites were found in the upper layers and there are significant associations between the habitats. The lower soil layers of the two species have the highest percentage of viable seeds. These results help us to understand more about the invasiveness of both species as related to their impacts on the seed banks and native vegetation. It also indicates that the native species that emerged from the invaded seed banks could be used for the restoration of the invaded habitats.

Impacts of anthropogenic disturbance on forest vegetation cover, health, and diversity within Doma forest reserve, Nigeria.

Forest encroachment is a common practice that has led to the destruction of canopy trees in the Guinea savanna part of Nigeria. This study investigated the influence of human activities on vegetation health and species composition of Doma forest reserve located in Nasarawa State, Nigeria. Landsat satellite data from 1986 to 2021 were utilized to assess forest cover change, land surface temperature (LST), and vegetation indices (VIs). The results show that dense woodland vegetation in the Doma forest reserve depreciated between 1991 and 1999 by 17.82% before increasing by 7.37% between 1999 and 2021. Similarly, vegetation greenness (measured by the Normalized Difference Vegetation Index (NDVI), Green Chlorophyll Vegetation Index (GCVI), and leaf area index (LAI)) of the forest mirrored the changes observed in the forest cover. The LST extracted for each year was correlated with all VIs, and an inverse relationship was observed in all relationships analyzed. The decline in greenness between 1999 and 2011 was attributed to increasing lumbering, bush burning, and sand dredging activities. Results also showed the current diversity state (H1 = 0.23), evenness (0.63), and the volume of tree (1.31 m3) species in the heart of the Doma forest reserve. However, a high (25%) native tree species in the Fabaceae family correlated with a dramatic increase in the VIs and an increase in dense woodland cover indicating the importance of Fabaceae in forest ecosystem regeneration.

Land use and land cover changes influence the land surface temperature and vegetation in Penang Island, Peninsular Malaysia.

The ecological changes in vegetation and land of an area can be monitored and managed through the assessment of its past and present land use and land cover (LULC). In this study, we assessed the changes in the LULC of Penang Island between 2010 and 2021. We also determined the corresponding impacts on the land surface temperature (LST) and vegetation index in the form of normalized difference vegetation index (NDVI). Landsat-5 and Landsat-8 were selected for the study. The LULC types were classified using both supervised and unsupervised multivariate maximum likelihood techniques. The LULC change analysis revealed a considerable increase in the urbanized areas (45.71%), a slight increase in the forests (1.57%) and a sizeable reduction in the agricultural/herbaceous areas (- 33.49) of the city within the stipulated period. The urbanized areas were observed to have the highest LST in 2010 and 2021 (28.75-34.0 °C) followed by the bare land (29.76-29 °C). The increase in temperature could have been driven by the reduction in the greenness of the city coupled with the openness of vegetation cover. Similarly, strong positive correlations were observed between the LST and NDVI in the urbanized areas (R2 = 0.92), and bare lands (R2 = 0.86). We, therefore, hypothesize that urbanization is the main driver of the LULC changes on Penang Island.

Patterns of ferns community assemblages in some Malaysian and Nigerian tropical forests.

Research on fern ecology has gained attention in the last decade, yet there is a paucity of information on the comparison of ferns communities across continents. This study focused on comparing the ferns community assemblages in some tropical forests of Malaysia and Nigeria, thereby assessing the patterns of species richness (SR) and phylogenetic diversity (PD) in relation to the bioclimatic drivers across the continents. The diversity and taxonomic compositions of ferns were assessed using 180 plots of 10 m × 10 m in each country. The species richness and other diversity indices were determined using the combined forests data for each country and for the individual forests. Also, the phylogenetic diversity of the ferns was assessed using the genus-based molecular sequences downloaded from the GeneBank. The patterns of the ferns SR and PD in the two countries as driven by some bioclimatic factors were evaluated using the regression analysis. The observed and rarefied-extrapolated fern species richness is significantly higher in Malaysian forests than in Nigerian forests. Also, the other diversity indices are significantly higher in Malaysian forests except for the Shannon index which showed no significant difference between the two biogeographic regions. There is a very low similarity (7.41%) in the taxonomic composition of ferns between the two biogeographic areas, although the similarity in composition increased with increasing taxonomic levels (species: 7.41%, genus: 12.77%, family: 70.96%). Terrestrial and epiphytic ferns are more dominant than the other life forms in the two countries. The precipitation variables drive the phylogenetic structure of ferns in Nigeria, whereas both precipitation and temperature variables drive the phylogenetic structure of ferns in Malaysia. This indicates that ferns assemblages in Nigeria and Malaysia are driven by both climatic variables. Besides, we also hypothesize that these observed differences could be due to other historical and evolutionary processes.

The impact of tantalite mining on the flora diversity in Nasarawa state, Nigeria.

The activities of the artisanals and small-scale miners in Nasarawa state, Nigeria, are increasing daily without considering the loss of biodiversity, which has continuously disrupted ecological functions and environmental balance. The study aimed at investigating the effect of tantalite mining activities on flora diversity. Three study sites were selected for floristic data collection, comprising tantalite mining site A situated in Azara, Awe LGA; tantalite mining site B situated in Tunga, Awe LGA; and referred site C situated along the Makurdi-Obi Road, Lafia LGA. Eight plots of 20 × 20 m were systematically placed along two transect lines of 1000 m with 500 m distance apart. The total numbers of 32 plant species, at the ratio of 11:20:21 individual species, were found in sites A, B, and referred site C, respectively. Tantalite mining site A showed 46% rare herbs dominating the site, with an introduction of new non-native species of Jateorhiza spp. and Hyptis suaveolens, presenting a significantly high number of individuals (p ˂ 0.0069). Tantalite site B, Tunga, had 50% reductions of several indigenous tree species such as Daniellia oliveri and Vitex doniana, while site A had 75% reduction of tree species. Therefore, the floristic diversity in site A endured a higher degradation than in site B. The indigenous species in site A were almost completely replaced with problematic weeds, invasive weed species, and non-native plant species. The tree diversities in sites A and B were seriously threatened, and H. suaveolens has been regarded as a potentially invasive plant species in Nasarawa state, Nigeria.