Influence of environment and substrate quality on root decomposition in naturally regenerating and restored Atlantic white cedar wetlands

Abstract

Restoration efforts and ecologically based management practices for Atlantic white cedar wetlands have recently focused on organic matter aggradation as an ecosystem function critical to this system’s maintenance. The objective of this study was to evaluate environmental and substrate quality factors influencing root decomposition in naturally recovering (reference) and restored Atlantic white cedar wetlands in southeastern Virginia and northeastern North Carolina. Chamaecyparis thyoides roots were used as a standard substrate to evaluate environmental influences. Roots native to each site were used to evaluate community-level decay dynamics. Standard root mass loss was similar across all sites. Surprisingly, substantial differences in hydrology and soil organic matter among sites did not influence standard root decay. Although regression analysis detected a significant relationship between soil pH and decomposition rates, no significant relationship was found with depth to ground water. Native root decomposition rates were similar among the reference sites, but were substantially faster on the restored sites. This suggests that litter quality exerts a strong controlling influence on decomposition in Atlantic white cedar wetlands. Native root decomposition rates were correlated with lignin concentration and L:N ratios, which were higher in the roots on the reference sites due to greater proportions of woody species. Nitrogen alone did not appear to be a major regulating factor for root decomposition on our sites. Our results imply that as soon as a restored Atlantic white cedar wetland develops a closed canopy of cedar, its decomposition dynamics are likely to equilibrate with natural mature stands.