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.

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.