Decomposition of mangrove roots depends on the bulk density they grew in

Abstract

Mangroves hold large organic carbon (C) stocks in their soils. These C stocks are mainly attributed to the high productivity and slow decomposition of the below-ground biomass. Rates of decomposition are strongly influenced by edaphic factors including soil bulk density (BD). Hence, this study assessed the influence of soil BD on mangrove root material and its effect on decomposition. To determine the effect of the BD in which the plants were grown on decomposition rates (i.e. mass loss), four mangrove species were grown in soils of six different BD. The root material was then placed in litterbags and incubated in mangrove forest soil for three months. Additionally, the root material was analysed for nitrogen (N) and phosphorus (P), as well as lignin and cellulose content. The soil BD experienced during root growth strongly affected mass loss, which decreased with increasing soil BD of the growth media. Decomposition also differed among species. Variation in mass loss was likely influenced by N levels, C:N ratios and lignin content of the root tissue. Variation in soil BD influences the C sequestration potential of mangroves, as BD affects the decomposability of mangrove root tissues.