Tuesday, 8 November 2005
202-4

This presentation is part of: Symposium--Wetlands in Arid Landscapes

Wetland Restoration & Water Quality Remediation: Upper Klamath Lake, Oregon.

Christopher B. Craft, Sean A. Graham, and Allison Aldous.

Forms, amounts and accumulation of soil phosphorus (P) were measured in natural and recently restored marshes surrounding Upper Klamath Lake located in south-central Oregon to determine rates of P accumulation in natural marshes and to assess changes in P pools caused by long-term drainage in recently restored marshes. Soil cores were collected from three natural marshes and radiometrically dated to determine recent (137Cs-based) and long-term (210Pb-based) rates of peat accretion and P accumulation. A second set of soil cores collected from the three natural marshes and from three recently restored marshes was analyzed using a modification of the Hedley procedure to determine the forms and amounts of soil P. Total P in the recently restored marshes (222 to 311 ug cm-3 was 2-3 times greater than in the natural marshes (103 to 117 ug cm-3 primarily due to greater bulk density caused by soil subsidence, a consequence of long-term marsh drainage. Occluded Fe and Al bound Pi, calcium bound Pi and residual P were 4 times, 22 times and 5 times greater, respectively in the recently restored marshes. More than 67% of the P pool in both the natural and recently restored marshes was present in recalcitrant forms (humic-acid Po and residual P) that provide long-term P storage in peat. Phosphorus accumulation in the natural marshes averaged 0.45 g m-2 yr-1 (137Cs) and 0.40 g m-2 yr-1 (210Pb), providing a benchmark for optimizing P sequestration in the recently restored marshes. Effective P sequestration in the recently restored marshes, however, will depend on re-establishing equilibrium between the P enriched soils and P concentration of floodwaters and a hydrologic regime similar to the natural marshes.

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