Decomposition dynamics in restored and naturally recovering Atlantic white cedar (Chamaecyparis thyoides) wetlands.

摘要

Restoration efforts and ecologically based management practices for Atlantic white cedar wetlands have recently focused on soil organic matter sequestration and aggradation as critical ecosystem functions in the maintenance of this imperiled community type. This work addresses how developmental stage, litter quality and environmental conditions influenced aboveground leaf litter and belowground root decay in naturally regenerating and restored Atlantic white cedar wetlands. Using standard litterbags for leaf litter and a modified litterbag technique for roots, decay dynamics of naturally regenerating and restored Atlantic white cedar stands were measured to compare ecosystem development trends with restoration conditions. Effects on rates of mass loss, nitrogen, phosphorus and carbon dynamics during decomposition of a common root and leaf litter type (Chamaecyparis thyoides) and native leaves and roots are discussed.; Native root decay was significantly faster at all depth intervals within the restoration setting compared to the stands along a chronosequence. In contrast, Chamaecyparis root decay was similar along the chronosequence and restoration setting. Native leaf litter decay was faster than Chamaecyparis leaf litter decay but no differences occurred among litter decay rates along the chronosequence and restoration setting.; Within all sites, native leaf litter and Chamaecyparis thyoides litter immobilized nitrogen over the course of the study, while phosphorus was released. Nitrogen in leaf litter was immobilized over two times initial amounts. Site hydrology and initial phosphorus content were strongly correlated with leaf litter decay rates.; Native roots and standard roots immobilized nitrogen and released phosphorus throughout the study. Roots accumulated nitrogen but increases were less pronounced relative to leaf litter. Root decay was highly correlated with initial phosphorus and lignin concentration and L:N ratio. Decay of Chamaecyparis roots were similar across all sites despite significant differences in site hydroperiod. Root decay was not correlated with site hydrology. With regards to native root material, these results suggest that within restored sites the current status of belowground carbon storage functions appear to be deficient in comparison to the naturally regenerating sites. Continued long-term study of these and similar restoration sites are needed to provide greater insight into appropriate recovery models for various wetland functions of Atlantic white cedar.