University of Vermont
Co-Authors: W. B. Bowden, K. L. Underwood, and E. D. Roy
The contribution of riparian wetland restoration to meeting phosphorus (P) load reductions in agricultural watersheds is uncertain, as many potential restoration sites overlay former agricultural soils that can contain legacy P. Hydrologic changes associated with restoration can potentially mobilize legacy soil P as soluble reactive P (SRP), decreasing net P retention efficiency. However, understanding of the general magnitude of SRP release versus retention of sediment-bound P during flooding remains very limited, as do the spatial and temporal dimensions of SRP release. We are using a multi-scale approach to develop indices of potential SRP loss risk. This is part of a broader research project focused on P dynamics in restored riparian wetlands in the Vermont portion of the Lake Champlain Basin. To date, we have conducted laboratory experiments using intact cores from 14 sites, from which we observed SRP release rates that span two orders of magnitude, with corresponding equilibrium SRP concentrations ranging from 0.01 to 1 mg P L-1. We are still evaluating possible predictors for intact core SRP flux, but preliminary results indicate that soil characteristics and landscape metrics are both important. Ongoing work includes additional intact core experiments and complementary field monitoring of P dynamics, as well as model development and simulations to determine the time horizon of legacy P impacts. Our ultimate goal is to inform site selection and design for riparian wetland restoration projects in Vermont so that P retention benefits are increased.