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

Abstract

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.

Early stages of root and leaf decomposition in Hawaiian forests: effects of nutrient availability

“…Each value represents a composite sample from four replicates rienced net release. The high levels of N immobilization in roots contrast with the low N immobilization potential of roots in tallgrass prairies (Seastedt et al 1992), but the occurrence of P release is in agreement with other studies (Seastedt 1988;Conn and Day 1996). The ability of roots to decompose faster than leaves but to retain N may indicate that roots serve an important role in N retention in these forests.…”

“…These results suggest that N and P limit root decomposition at the old, 4.1-Myear-old site, but not in the young, 300-year-old soils. The only other study that has examined root decay after N-fertilization found enhanced mass loss on two young dune sites but not on the oldest dune site (Conn and Day 1996).…”

“…Root decomposition in relation to fertilization has only been examined in one study, and results varied with the successional age of the vegetation. On 24-and 36-year-old barrier dune islands in Virginia, root decomposition rates were faster with N addition, but N fertilization had no effect on root decomposition on 120-year-old dunes (Conn and Day 1996).…”

“…In addition, the observation that decaying litter undergoes net immobilization of nutrients is also interpreted as evidence of nutrient limitation (Prescott 1995). Because exogenous nutrients are necessary for immobilization, fertilization should increase net immobilization (Conn and Day 1996). Yet even under circumstances where nutrients have been demonstrated to limit aboveground net primary productivity, fertilization does not always stimulate increased mass loss rates, as evidenced at the 300-yearold site and in a Pinus radiata plantation in Australia (Theodorou and Bowen 1990).…”

Differential responses of needle and branch order-based root decay to nitrogen addition: dominant effects of acid-unhydrolyzable residue and microbial enzymes

“…However, traditional research on these relationships has focused primarily on the aboveground plant tissues such as foliage (Hobbie 2008;Perakis et al 2012). Although a growing body of studies suggest that root-derived materials may contribute more to stabilizing soil organic matter than foliage (Rasse et al 2005;Crow et al 2009), empirical evidence for the effect of increased N availability on the afterlife of fine roots remains lacking (Conn and Day 1996;Ostertag and Hobbie 1999;Mao et al 2011;Norris et al 2013;Solly et al 2014). This, to a large extent, impedes further understanding of the responses of plant tissue decomposition to increased N availability on a broader scale, and the underlying response mechanisms.…”