Soil Conditions Following Hydrologic Restoration in Cypress Dome Wetlands

摘要

Soil characteristics and decomposition rates were investigated in 12 geographically isolated wetlands (cypress domes) across a gradient of hydrologic alteration (altered, marginally altered and least altered sites) seven years after passive recovery from historic groundwater withdrawals. Above- and belowground decomposition rates were determined in transition (seasonally flooded) and outer deep (semi-permanently) hydrologic zones. Flood duration, frequency, redox conditions, pH, and soil organic matter were measured to potentially explain patterns across the alteration gradient. Despite the reduction in groundwater withdrawals, altered sites exhibited fewer days of inundation in transition and outer deep zones compared to marginally altered and least altered wetlands. Over a 56week period, altered wetlands displayed greater decomposition in the aboveground outer deep zone (73.3 +/- 4.0% mass remaining) and in the belowground transition zone (62.0 +/- 4.5% mass remaining) compared to marginally and least altered sites. Analyses indicated that marginally altered wetlands were more comparable to least altered wetlands however differences in altered wetland soils (including decomposition) persist. Although wetland hydrology has been partially restored, additional time and/or further site augmentation may be needed for altered sites to be functionally equivalent to least altered wetlands and in some cases (e.g., excessive subsidence) the degree of past alteration may limit restoration potential.