Structure and biomass accumulation of natural mangrove forest at Gazi Bay, Kenya

Abstract

Abstract. Githaiga MN, Kotut K, Kariuki F, Kairo JG. 2020. Structure and biomass accumulation of natural mangrove forest at Gazi Bay, Kenya. Bonorowo Wetlands 10: 18-32. This study aimed to determine the forest structure and estimate biomass accumulation above and below ground in the mangrove forest of Gazi Bay. The Gazi Bay mangrove forest's western, middle, and eastern forest blocks were investigated for forest structure, whereas the western forest block was determined for biomass accumulation. To calculate below-ground biomass accumulation, in-growth cores of 80 cm long, 20 cm broad, and 60 cm deep were employed. Above-ground biomass accumulation was calculated using tree height and stem diameter data at breast height (DBH-₁₃₀). Tagging shoots observed leaf phenology. At the start, environmental variables were measured every four months for a year across four mangrove species zones. The linear regeneration sampling approach determined natural regeneration's composition and distribution pattern (LRS). Salinity revealed a strong negative connection with above-ground biomass accumulation among the soil environment characteristics studied. Sonneratia alba had the highest biomass accretion rate of 10.5 1.9 t ha-1 yr-1 among the four forest zones. Rhizophora mucronata (8.5 0.8 t ha^-1 yr^-1), Avicennia marina (5.2 1.8 t ha^-1 yr^-1), and Ceriops tagal (2.6 1.5 t ha^-1 yr^-1) were the next most abundant species. Above-ground and below-ground biomass accumulation differed significantly among zones (F _{(3, 8)} = 5.42, p = 0.025) and (F _{(3, 8)} = 16.03, p = 0 001), respectively. There was a significant difference in total biomass accumulation across zones (F _{(3, 8)} =15.56, p = 0.001). A root: shoot biomass accumulation ratio of 2: 5 was calculated for the entire forest. This study's findings provide more accurate estimates of mangrove carbon capture and storage, which can be used in carbon credit discussions in the emerging carbon market.