IMPACT OF RIGHT-OF-WAY CONSTRUCTION ON ORGANIC SOIL BULK DENSITY IN THE RED LAKE PEATLAND

Abstract

The objective of this study was to evaluate changes in soil bulk density associated with construction of a 500-kV transmission right-of-way (ROW) across a peatland in northwestern Minnesota. Immediately before (1979), and for 2 yr following construction (1980, 1981), bulk density of the organic soil within the ROW and in undisturbed control areas was monitored. Soils were primarily Typic Mesisols (Borohemists), with some Mesic Fibrisols (Sphagnofibrists). Monitoring was carried out in five vegetation types, ranging from graminoid fen to treed bog. Soil bulk density was determined in 25-cm increments to 1 m. There were no significant differences in density between the ROW and the control before construction. When data for the 2 yr following construction were combined, results showed significantly higher density in the surface of the ROW than in the surface of the controls. Absolute differences were small, however. The density in the ROW was 5% higher and that in the controls 5% lower than the overall mean of 0.052 g∙cm−3. Largest differences were in a vegetation type with a fibric surface, the treed fen, where, in 1981, the surface in the control had a bulk density of 0.033 g∙cm3, and in the ROW, 0.049 g∙cm−3. Because of high hydraulic conductivity at both densities, any present restriction of water flow across the peatland is unlikely. Key words: Transmission lines, water flow, histosols, Minnesota