Carbon stocks in the mangrove ecosystem of Rufiji river delta, Rufiji district, Tanzania

Abstract

One of the most important ecosystem services provided by mangrove ecosystems is to act as a carbon sink. Despite this role, most carbon storage studies in Tanzania have concentrated on terrestrial ecosystems. In this study, carbon and volume prediction models were developed for the mangrove ecosystem in Rufiji River Delta, Tanzania. The models developed were used to estimate carbon. Soil organic carbon as an important carbon reservoir was also assessed at different depths. Biomass and volume prediction models were developed using linear regression from a destructive sample of 50 trees spanning a wide range of DBH size classes. Soil organic carbon was analyzed by wet oxidation method. Biomass models were developed for stems, branches, roots, leaves and twigs and volume prediction models for total volume. All linear and power form models developed were significant at P<0.05 and P<O.OOI,respectively. The organic carbon was 39.61 t ha I, 28.04 t ha' and 32.85 t ha-I at 0-15 em, 15-30 em and 30-60 em, respectively. The Rufiji River Delta mangrove ecosystem was estimated to have 40.5 t ha-I of aboveground carbon, 21.08 t ha-I of belowground carbon (roots) and 98.57 t ha-I of soil organic carbon. The soil organic carbon (39.61 t ha-I ) at surface layer (0-15 ern) was significantly higher than at 15-30 ern (28.04 t ha") and 30-60 em depth (32.85 t ha") (P<0.05). Rhizophora mucronata contributed the highest (39.87%) biomass C, followed by Avicennia marina (28.06%). Sonneratia alba (2.58%) and Lumnitzera racemosa contributed the least (1.98%). Volume was estimated at 168.85 rrr' ha-I with Rhizophora mucronata contributing 39.3% and Avicennia marina 27.1% of the total volume. Overall, soil organic C (61.6%) was almost twice that of vegetation carbon contributing 38.4% emphasizing the role of soil as an important carbon reservoir in mangrove ecosystems. The Rufiji River Delta mangrove ecosystem has a high potential as an important carbon sink useful for climate change mitigation through sustainable management.