WOODY PLANT SPECIES COMPOSITION, RICHNESS AND CARBON STORAGE IN DISTURBED TROPICAL RIPARIAN FORESTS

Abstract

Riparian forests play a vital role in the functioning of river systems and biodiversity protection. However, rapid land use and land cover changes due to human activities have led to their degradation and loss of valuable environmental services they offer. To plan for wise use and facilitate development of improved management strategies, it is important to understand riparian forests structure and carbon storage particularly for sites that are not fully protected. Therefore, a study was carried out to determine woody plant species composition, density, richness and above ground carbon storage in disturbed riparian forests of Morogoro, Tanzania. Thirty (30) sampling plots measuring 10 x 20 m each were laid systematically along 3 sites and all woody plant species with diameter at breast height (Dbh) of ≥ 1 cm identified. In total, 65 woody plant species belonging to 58 genera and 27 families were recorded. Four dominant families were Moraceae (42.2%), Apocynaceae (13%), Annonaceae (10.3%) and Phyllanthaceae (7.8%). The Dbh size class distribution showed a slight deviation from the classical inverse J distribution suggesting that both small and large sized trees are harvested. The average overall stocking density in the plots was 1598 stems ha-1 (range 250-3950) while the overall mean carbon stored in the plot was 76.5 t ha-1 (range 11.4-272.7). Ficus exasperata, Syzygium cumini and Voacanga africana contributed 36% of the carbon. There were no significant differences (one-way ANOVA; in all cases P > 0.05) in stem density, species richness and carbon stocks between sites. This study has revealed that even though the study forests are not fully protected they have high species richness, stem density and above ground carbon and therefore improved management is recommended to maintain the structure and functions of the remaining riparian forests in Kilombero.

Key words: River systems, basin, distribution, density, biomass, land use, Kilombero