Response of root and cotton strip decay to nitrogen amendment along a barrier island dune chronosequence

The influence of nitrogen amendment on fine root decomposition was evaluated on sites located along a barrier island chronosequence (24-, 36-, and 120-year-old dunes). The degree to which exogenous nitrogen limits decay at each site was evaluated through a fertilization experiment. Decay substrates included native roots and cotton strips that differed in carbon and nitrogen chemistries. Root decay on younger sites (24 and 36 years old) showed a slight but significant increase in native root decay in response to fertilization. Cotton strips decayed significantly faster in response to fertilization on all sites during three different time periods except on the oldest site in the winter-spring. Nitrogen mineralization and soil nitrogen availability responded to fertilization in a manner consistent with nitrogen limitation. Nitrogen immobilization potential was low in unfertilized plots and increased on younger sites as a result of fertilization. Suppressed lignin degradation in 120-year-old dune roots suggested possible negative fertilization effects. Pure cellulose (cotton strips) did not demonstrate this suppression. It was concluded that nitrogen was a limiting factor during root decay in younger sites but not on the older 120-year-old dune site.