Research Results
A key result has been the discovery that the grey mangrove (Avicennia marina) is a dominant species when replanted – it grows vigorously, has a high survival rate, and also appears to facilitate growth and natural recruitment of other species, making it ideal for restoration efforts.
Experiments regarding tree survival have tested species, treatment and various environmental variables. Results have demonstrated that salinity is the most important determinant of survival, with Bruguiera species showing particular sensitivity. The size of plot and size of tree at planting have been shown to have little effect, which has relevance for the economics of restoration, as there is therefore no reason to keep trees in nurseries until they reach a large size. Density has also been shown to be a key factor, with results showing highest percentage survival after 702 days in the highest density plots and lowest survival in the lowest density plots.
Mangroves store large amounts (up to 50%) of their total carbon absorption in their roots, and some of these roots may become permanent carbon stores in the form of peat. As a result, in September 2007, over 2,000 mangrove trees had been planted on the project and conservative estimates predict that 180 tons of carbon could be absorbed over 25 years of forest growth.
Huxham, M., Kumara, M. P., Jayatissa, L.P., Krauss, K.W., Kairo, J., Langat, J., Mencuccini, M., Skov, M.W. & Kirui, B. (2010) Intra and inter- specific facilitation in mangroves may increase resilience to climate change threats. Philosophical Transactions of the Royal Society B,365 (1549): 2127-2135
Huxham, M., Langat, J., Tamooh, F., Kennedy, H., Mencuccini, M., Skov, M.W. & Kairo, J.G. (2010). Decomposition of mangrove roots: effects of tree species and tidal height in a Kenyan forest. Estuarine Coastal and Shelf Science: 1-8
Kirui, B.Y.K., Huxham, M., Kairo, J. & Skov, M. (2008) Influence of species richness and environmental context on early survival of replanted mangroves at Gazi bay, Kenya. Hydrobiologia, 603: 171-181
Tamooh, F., Huxham, M., Karachi, M., Mencuccini, M., Kairo, J.G. & Kirui, B. 2008. Below-ground root yield and distribution in natural and replanted mangrove forests at Gazi bay, Kenya. Forest Ecology and Management, 256: 1290–1297