Effects Of Small-Scale Limestone Mining On Floristic Composition And Plant Species Diversity In Nanyala Village, Mbozi District, Tanzania

ABSTRACT

A study was conducted in Nanyala Village, Mbozi District, southwestern Tanzania to determine the effects of small-scale limestone mining on floristic composition and species diversity of shrubs and herbs, and on plant community characteristics. A stratified random sampling technique was adopted. One hundred plots (5 × 5 m) and 500 plots (0.5 × 0.5 m) were established systematically in each stratum at both mined and unmined sites for sampling shrubs and herbs, respectively. The total count method was adopted for shrubs and point sampling for herbs species where individual species were recorded. The data were analysed for frequency, diversity and density. Floristic composition for shrubs was significantly lower at mined than unmined sites, and the opposite was the case for herbs. One hundred forty two species in 40 families and 101 genera were recorded. The most frequent shrub family and species at the mined sites were Fabaceae (24%), and Senna singueana (10%), respectively. At the unmined sites, Fabaceae (88%) and Vernonia exsertiflora (55%) were the most frequent. For herbs, Poaceae (73%) and Chloris pycnothrix (21.4%) were the most frequent taxa at the mined site, while Poaceae (83%) and Fimbristylis hispidula were the most frequent taxa at the unmined sites. Shrub species diversity varied significantly; with unmined sites having higher diversity (H’=3.176) than mined sites (H´=2.687). For herbs, mined sites has higher diversity (H´=3.205) than unmined (H´=1.971) sites. Shrub species density was higher at unmined (68.25±14.5 SE individuals ha-1 ) than mined sites (11.88±3.576 SE individuals ha-1 ). PCA analysis showed two distinct communities: the Senna singueana- Markhamia obtusifolia for mined sites, and the Vernonia exertifloraBrachystegia speciformis for the unmined sites. The study concludes with recommendations for effective management of small-scale mining in Nanyala Village, to avert adverse environmental effects.