Litter Fall Dynamics of Restored Mangroves (Rhizophora mucronata Lamk. and Sonneratia alba Sm.) in Kenya

Abstract

Mangrove forests are active carbon sinks and important for nutrient cycling in coastal ecosystems. Restoration of degraded mangrove habitats enhances return of ecosystem goods and services, including carbon sequestration. Our objective was to assess the restoration of primary productivity of reforested mangrove stands in comparison with natural reference stands in Gazi Bay, Kenya. Litter fall data were collected in nine Rhizophora mucronata and Sonneratia alba monospecific stands by use of litter traps over 2 years. Litter was emptied monthly, dried, sorted, and weighed. The reforested and natural stands showed seasonality patterns only in the production of reproductive material. Leaves constituted the highest percentage to total litter fall. Litter productivity rates for the R. mucronata stands were not significantly different and ranged from 6.61–10.15 to 8.36–11.02 t ha−1 yr−1 for the restored and natural stands, respectively. The productivity of 5 years R. mucronata stands reached 5.22 t ha−1 yr−1 and was significantly different from other stands. Litter productivity rates for S. alba stands was 7.77–7.85 for the restored stands and 10.15 t ha−1 yr−1 for the natural stand but differences were not significant. Our results indicate that plantations of at least 11 years have attained litter productivity rates comparable to the natural forests. This suggests that productivity of replanted mangroves is likely to reach complete recovery by this age under the prevailing environmental conditions.