Mangrove rehabilitation dynamics and soil organic carbon changes as a result of full hydraulic restoration and re-grading of a previously intensively managed shrimp pond

Hydraulic restoration by opening the shrimp pond banks facilitated the establishment of planted mangroves and colonisation by non-planted mangrove species and was shown to be an effective method of mangrove rehabilitation. Planted Rhizophora apiculata and Rhizophora mucronata had grown significantly in 6 years, to 300 and 350 cm, respectively. However, the growth rate of Bruguiera cylindrica was merely 150 cm in the same period despite vigorous growth in the initial stage. About 15 non-planted mangrove species had colonised within 6 years after reopening the banks, with the dominant species being Avicennia marina (46.9%) followed by B. cylindrica (27.0%) and Ceriops tagal (14.9%). After the enhancement, soil organic carbon increased considerably from 110 to 160 tonC ha(-1) in 2 years at the lower elevation, indicating that hydraulic restoration could stimulate carbon recovery through enhancement of mangrove growth. However, soil organic carbon decreased by almost half in the higher ground, suggesting that carbon decomposition was accelerated due to drying of soils.