Godgift Swai

Assessment of Plant Diversity and Ecological Status of the Coastal Tanzania Forests: A Case Study of Mafia Island, Coastal Forest Mosaic

Coastal forests are famously known for their high biodiversity values as well as multiple uses. They are sources of medicinal plants, fuelwood, building materials, food, and they help to maintain a regular water supply for towns and villages. Despite their importance, both in terms of biodiversity and use, there is rapid degradation in these forests due to advancing human population pressure and urbanization. It is on this ground, this study has to be conducted in Mafia Island Coastal Forest Mosaic in order to assess the assess species richness and diversity, species composition, distribution and levels of endemism hence the plant diversity and ecological status. The study was done in Mlola and Juani island forest reserves in Mafia Island.

We collected the data using a systematic sampling, adopted for the two sites (Mlola and Juani forest reserves). Over 30 plots had been established in the two sites aiming at a sampling intensity of 10% to ensure justifiable sample size. We used circular plots of 15m radii with stratification of 1m, 5m, and 10m and 15m established to assess plants from herbs to woody stems as well as the regenerants and coppices. For woody plants Diameter at Breast Height (DBH) and heights of stems exceeding 4cm DBH were measured. These enabled calculation of forest parameters i.e., the number of stems per ha (N), basal area per hectare (G) m2 ha-1, and volume per hectare (V) m3 ha-1.

The data on forest stand parameters i.e. (N), (G) and (V) were computed and analyzed using Microsoft excel spreadsheet. Data analysis on species richness and diversity in the forest reserve were estimated using Species Diversity Indices (Maguran et al., 1988). Similarity in terms of species composition among the sites was determined using the Sorenson’s index.

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