Journals Proceedings

Abstract

Coastal wetlands are experiencing sea level rise, global warming and vegetation shift due to climate change. Climate change may influence soil organic matter mineralization, which plays an important role as a sink for atmospheric carbon; therefore it is important to identify the impact of hydrological processes on soil organic matter. We investigated how soil organic matter content responds to hydroperiod (i.e., the length of time portion of year during which the wetland area is waterlogged), distance from the river mouth and soil moisture content in subtropical Fukido riverine mangrove on Ishigaki Island. The relationships between soil organic matter with the hydroperiod, moisture and distance from the river mouth were analyzed by performing principle component analysis (PCA) on the log-transformed data set and by simple correlations. The organic matter in the sediments ranged between 5.8 and 23.1 %, with an average of 12.3 ± 3.3 % (SD) and decreased from river side to landward side. Our results show that soil organic matter presents strong positive correlations with soil moisture (r = 0.88, p < 0.01) and hydroperiod (r = 0.53, p < 0.05) and a strong negative correlation with the oxidation-redox potential (r = -0.81, p < 0.01). These results revealed that variation in soil inundation and moisture content affect the amount of organic matter in the sediments. Our data support the conclusion that sea level rise, might alter early diagenesis in mangrove sediments, and therefore the fluxes of nutrients in coastal ecosystems and the role of organic matter as a sink for atmospheric carbon.