Shuijing Zhai

Tidal marshes have been shown to be important recycling surfaces for biogenic silica (BSi) and macro- and microelements at the land-sea interface, and also as key places to probe into the decomposition process of wetland plant litters. In this study, in situ decomposition experiments were conducted with Phragmites australis, Cyperus malaccensis, and Spartina alterniflora in the Min River estuary wetland. Litterbags of 0.2 mm mesh size were used to evaluate the litter decomposition process and litter residual amounts of BSi and macro- and microelements, including carbon (C), nitrogen (N), Chromium (Cr), Cuprum (Cu), Cadmium (Cd), Zinc (Zn), Plumbum (Pb), Aluminum (Al), Manganese (Mn) and Ferrum (Fe), for a period of 520 days. The litter decomposition rate significantly differed among species in the following order: C. malaccensis (0.005 d-1) > S. alterniflora (0.004 d-1) > P. australis (0.003 d-1) with a BSi release rate of 98.64 %, 97.23 %, and 96.75 %, respectively. Although there were net release of BSi, C, and N from the three litters, continuous decrease of BSi/(C, N) ratio indicated that BSi removed from the litters much faster than C and N. Accumulation index results showed that Cu, Pb, Al, and Fe were net accumulated of in the litters while Cd, Mn, Cr, and Zn were predominantly released during the litter decay. Pearson correlation analysis results showed that the amounts of N, Cu, Cd, Pb, Al, and Fe in the litter presumably restrained the release of BSi from the litter with significant adverse correlation. These findings in the Min River estuary have important implications for geochemical cycles within the wetland system and for transport processes of potential nutrients out of the system.