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Ishee, Eulaila Rae

Plant and Soil Science

2011

MS

Lake Champlain has persistent algal blooms associated with excess phosphorus (P) from the landscape. Streambank erosion is ubiquitous throughout the Champlain Basin with 74% ofVennont stream reaches classified as unstable. The P contribution of streambank erosion has not been well quantified, yet could be a significant source of nonpoint P. The objectives of this study were to 1) assess the variability in total P (TP) and soil test P (MM-P) for eroding riparian soils across a large study extent and to depth; 2) relate TP and MM-P with soil physical and chemical properties, including texture, AI, Ca, and Fe; 3) relate TP and MM-P to landscape parameters, including land use/land cover (LULC), landscape position, soil type and parent material; and 4) quantify the potential P load from eroding streambanks.
Soil samples were taken from 76 erosion features to a depth of 90 cm on 4 streams in Chittenden County, Vermont and analyzed for texture, total P, Modified-Morgan's P, and total aluminum, calcium, iron, and manganese. Landscape parameters were assessed using available spatial databases for LULC, parent material, soil type, landscape position. Mean concentrations of TP and MM-P were similar among the four streams and through depth. A strong relationship found between Ca and TP in excess of apatite ratios suggests apatite-P could be a common P form in these soils. Low MM-P concentrations indicate that eroded streambanks may act as sinks rather than a source of P. Soil test P (MM-P) concentrations were not related to TP. Specific landscape parameters including LULC, landscape position, and parent material correlated with TP and MM-P. Eroding streambank soil from four streams in Chittenden County contained a total of 12.7 MT (7.1 - 19.4) of TP and 39.8 kg (36.2 -43.1) of MM-P. Estimated potential P load from eroding streambanks from 1999-2004 averaged 54% of total non-point load for three stream corridors, ranging from 22 to 84% for individual streams.