Weizhi Lu, Luzhen Chen, Wenqing Wang, Nora

Fung-Yee Tam, Guanghui Lin.Acta Oecologica,2013.49: 83-91.

Mangroves will either face longer tidal

inundation or retreat landwards in response to on-going acceleratedsea level

rise. However, little is known about the growth, regeneration or colonization

ofmangrove seedlings under the different tidal inundation regimes associated

with accelerated sea levelrise. In the present study, a field survey and a

greenhouse mesocosm experiment were conducted toevaluate possible effects of

accelerated sea level rise on colonization, establishment and seedling growthof

a mangrove pioneer species, Avicennia marina. Avicennia populations at

different elevations of theintertidal zone on Xiamen Island in Fujian Province,

China showed distinctive patterns in both seedlingdensity and plant age. The

seedlings at lower elevations had less annual biomass accumulation

andpopulation productivity, but higher shoot to root ratios, suggesting that

elevation has positive effects onseedling growth. The greenhouse mesocosm experiment

with 1-year-old A. marina seedlings utilized fiveinundation periods (0, 2, 4, 6

and 12 h in a semidiurnal tidal cycle) and two inundation depths (rootimmersion

and canopy immersion). Both inundation period and depth exerted significant and

negativeeffects on biomass accumulation, photosynthetic rate, leaf electron

transportation and water use efficiency.However, the negative effects of canopy

immersion were more profound than root immersion.Canopy immersion exacerbated

the effects of prolonged inundation, with no seedlings surviving undercanopy

immersion at the 12-hour treatment. These results suggest that at lower

elevations with highersea level, canopy immersion will have greater negative

effects on seedling colonization, establishmentand early growth of A. marina.

This finding is instrumental in predicting the future dynamics of

mangroveforests under increasing sea levels.

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