Authors: M P Kumara L P Jayatissa K W Krauss D H Phillips M Huxham
Publish Date: 2010/07/01
Volume: 164, Issue: 2, Pages: 545-553
Abstract
Survival growth aboveground biomass accumulation sediment surface elevation dynamics and nitrogen accumulation in sediments were studied in experimental treatments planted with four different densities 696 326 193 and 095 seedlings m−2 of the mangrove Rhizophora mucronata in Puttalam Lagoon Sri Lanka Measurements were taken over a period of 1171 days and were compared with those from unplanted controls Trees at the lowest density showed significantly reduced survival whilst measures of individual tree growth did not differ among treatments Rates of surface sediment accretion means ± SE were 130 ±13 105 ±09 84 ±03 69 ±05 and 57 ±03 mm year−1 at planting densities of 696 326 193 095 and 0 unplanted control seedlings m−2 respectively showing highly significant differences among treatments Mean ±SE rates of surface elevation change were much lower than rates of accretion at 28 ±02 16 ±01 11 ±02 06 ±02 and −03 ±01 mm year−1 for 696 326 193 095 and 0 seedlings m−2 respectively All planted treatments accumulated greater nitrogen concentrations in the sediment compared to the unplanted control Sediment N was significantly different among densities which suggests one potential causal mechanism for the facilitatory effects observed high densities of plants potentially contribute to the accretion of greater amounts of nutrient rich sediment While this potential process needs further research this study demonstrated how higher densities of mangroves enhance rates of sediment accretion and surface elevation processes that may be crucial in mangrove ecosystem adaptation to sealevel rise There was no evidence that increasing plant density evoked a tradeoff with growth and survival of the planted trees Rather facilitatory effects enhanced survival at high densities suggesting that managers may be able to take advantage of high plantation densities to help mitigate sealevel rise effects by encouraging positive sediment surface elevationWe gratefully acknowledge Earthwatch Institute and Zurich International for providing funds for this 4year mangrove restoration study in Sri Lanka Thanks to Mr Daglas Thisera Small Fishers Federation of Lanka for field coordination Collaborative research logistics from University of Ruhuna Sri Lanka and Edinburgh Napier University Scotland are also acknowledged Any use of trade product or firm names is for descriptive purposes only and does not imply endorsement by the US Government We confirm that this research complied with the current laws of Sri Lanka
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