High mangrove density enhances surface accretion, surface elevation change, and tree survival in coastal areas susceptible to sea-level rise

Oecologia
By: , and 

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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 (6.96, 3.26, 1.93 and 0.95 seedlings m−2) of the mangrove Rhizophora mucronata in Puttalam Lagoon, Sri Lanka. Measurements were taken over a period of 1,171 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 13.0 (±1.3), 10.5 (±0.9), 8.4 (±0.3), 6.9 (±0.5) and 5.7 (±0.3) mm year−1 at planting densities of 6.96, 3.26, 1.93, 0.95, 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 2.8 (±0.2), 1.6 (±0.1), 1.1 (±0.2), 0.6 (±0.2) and −0.3 (±0.1) mm year−1 for 6.96, 3.26, 1.93, 0.95, 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 sea-level rise. There was no evidence that increasing plant density evoked a trade-off 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 sea-level rise effects by encouraging positive sediment surface elevation.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title High mangrove density enhances surface accretion, surface elevation change, and tree survival in coastal areas susceptible to sea-level rise
Series title Oecologia
DOI 10.1007/s00442-010-1705-2
Volume 164
Issue 2
Year Published 2010
Language English
Publisher Springer-Verlag
Contributing office(s) Wetland and Aquatic Research Center, National Wetlands Research Center
Description 9 p.
First page 545
Last page 553
Country Sri Lanka
Other Geospatial Puttalam Lagoon