Native tree species diversity, structure and regeneration of Mashoza Remnant Natural Forest in Eastern Rwanda

Abstract

A remnant forest is a fragmented area of a formerly extensive forest that has survived through significant disturbances, often characterized by the presence of remnant trees. Mashoza remnant forest preserves a variety of biological diversity. However, human pressure has caused reduction of its biodiversity. By assessing the tree species diversity, composition and regeneration of native trees in Mashoza remnant natural forest in the eastern Rwanda to fill the gaps on data on the remnant forest and therefore generate a baseline data to researchers, policymakers. Sampling plots of 20 by 20 meters were used for the tree species inventory. Plots were situated within the forest precisely from 50 meters far the edge to avoid edge effect. The sampling plots were located on hills and in valleys in southern, central, and northern parts of the forest. On each hill, three sites were chosen on foot, in the center, and on the top of the hill and in valley. In each plot, species diversity and abundance of adult trees, saplings, and seedlings were recorded. Every tree species in each plot was identified and registered. The height and DBH of all trees inside the plots were measured for all trees with a DBH of at least 5 cm, using a Suunto Clinometer PM-5/360PC and a diameter tape. Samplings and seedlings were counted and recorded in each sample plot and R (vegan package) studio has been used for data analysis. In total, 27 tree species were identified in the Mashoza remnant natural forest and no statistical difference was observed in terms of tree species diversity in sites located on hill foot, middle, and top of the hills neither in valleys. Higher values of the Evenness index in the foot (0.42) than in the middle (0.40) and the top (0.28) indicate a higher degree of evenness and diversity of species in the central regions of the hill. There is less diversity in the top and foot compared to the middle part of the hills in the forest. With over 24 adult trees, 88 saplings, and 44seedlings, the Mashoza remnant natural forest demonstrates a promising low capacity for recovery and self-sustainability. The seedlings are less than samplings indicating a problem of survival of seedlings in the forest. As the study was conducted in the dry season, it is recommended that further studies be conducted in rain season to understand the reason behind the less numerous seedlings in the forest. In addition, the Mashoza remnant forest should be protected because of its biodiversity and particularly its tree species diversity, which can serve as a gene pool for important native tree species.