Hydrologic Regime Controls Soil Phosphorus Fluxes in Restoration and Undisturbed Wetlands

Authors

  • Allison Aldous,

    Corresponding author
    1. The Nature Conservancy, 821 SE. 14th Avenue, Portland, OR 97214, U.S.A.
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  • Paul McCormick,

    1. Everglades Program Team, Loxahatchee National Wildlife Refuge, 10216 Lee Road, Boynton Beach, FL 33478, U.S.A.
    2. Present address: U.S. Geological Survey, Leetown Science Center, 11649 Leetown Road, Kearneysville, WV 25430, U.S.A.
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  • Chad Ferguson,

    1. The Nature Conservancy, 821 SE. 14th Avenue, Portland, OR 97214, U.S.A.
    2. Present address: Institute for Environmental Quality, Wright State University, 3640 Colonel Glenn Highway, Dayton, OH 45435, U.S.A.
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  • Sean Graham,

    1. School of Public and Environmental Affairs, Indiana University, 1315 E. 10th Street, Bloomington, IN 47405, U.S.A.
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  • Chris Craft

    1. School of Public and Environmental Affairs, Indiana University, 1315 E. 10th Street, Bloomington, IN 47405, U.S.A.
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Address correspondence to A. Aldous, email aaldous@tnc.org

Abstract

Many wetland restoration projects occur on former agricultural soils that have a history of disturbance and fertilization, making them prone to phosphorus (P) release upon flooding. To study the relationship between P release and hydrologic regime, we collected soil cores from three restoration wetlands and three undisturbed wetlands around Upper Klamath Lake in southern Oregon, U.S.A. Soil cores were subjected to one of three hydrologic regimes—flooded, moist, and dry—for 7.5 weeks, and P fluxes were measured upon reflooding. Soils from restoration wetlands released P upon reflooding regardless of the hydrologic regime, with the greatest releases coming from soils that had been flooded or dried. Undisturbed wetland soils released P only after drying. Patterns in P release can be explained by a combination of physical and biological processes, including the release of iron-bound P due to anoxia in the flooded treatment and the mineralization of organic P under aerobic conditions in the dry treatment. Higher rates of soil P release from restoration wetland soils, particularly under flooded conditions, were associated with higher total P concentrations compared with undisturbed wetland soils. We conclude that maintaining moist soil is the means to minimize P release from recently flooded wetland soils. Alternatively, prolonged flooding provides a means of liberating excess labile P from former agricultural soils while minimizing continued organic P mineralization and soil subsidence.

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