Dynamics and characteristics of biogenic silica and macro- and microelements in decomposing litter in the Min River estuary, southeast China

摘要

Tidal marshes are important recycling areas for biogenic silica (BSi) and macro- and microelements at theland–sea interface and are key locations for examining the decomposition process of wetland plant litter. Inthis study, in situ decomposition experiments were conducted with Phragmites australis, Cyperusmalaccensis, and Spartina alterniflora in the Min River estuary wetland. Litterbags of 0.2-mm mesh sizewere used to evaluate the litter decomposition process and residual values of BSi and macro- andmicroelements, including C, N, Cr, Cu, Cd, Zn, Pb, Al, Mn, and Fe over 520 days. The litter decompositionrate 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 BSi release rates of 98.64%, 96.75%, and 97.23%,respectively. Although there were net releases of BSi, C, and N from the three litter species, continuousdecrease in the BSi/(C, N) ratio indicated that BSi was removed from the litter much faster than C and N. Theaccumulation index results showed that Cu, Pb, Al, and Fe were net-accumulated in the litter, whereas Cd, Mn,Cr, and Zn were predominantly released during litter decay. Pearson’s correlation analysis results showed thatthe amounts of N, Cu, Cd, Pb, Al, and Fe in the litter restrained BSi release with a significant negativecorrelation. These findings in the Min River estuary have important implications for geochemical cycleswithin wetland systems and the transport processes of potential nutrients out of the system.