Litter decomposition processes in a floodplain forest

Litter decomposition processes were studied in a floodplain forest in South Carolina. Annual decomposition of mixed leaf species decreased from 85% at the streambank to 58% in the contiguous upland terrace forest. This decrease in weight loss was correlated with reduced flooding and an increase in more resistant litter substrates at the upland terrace. Species-specific studies indicated that sweet gum leaves decomposed more slowly than red maple, black gum and red ash. Sweet gum leaves had higher initial lignin and cellulose concentrations and larger C:N ratios than the other species. Nutrient release rates from litter varied across the floodplain. Magnesium and K leached quite rapidly within the floodplain, whereas Ca and N losses were more gradual. In contrast, Mg and K losses were less and Ca and N immobilization occurred in the more resistant litter on the unflooded upland terrace. The patterns of nutrient release were generally similar for the four floodplain species tested. Decomposition and recycling processes are different on the floodplain and upland terrace forest. Intrasystem nutrient cycling appears tight in the sandy, nutrient-poor upland terrace forest. Mechanisms such as litter burial during flooding and the timing of nutrient mineralization can limit nutrient export from the floodplain forest.