Recovery of chemical and physical properties of boreal plain soils impacted by pipeline burial

Pipeline construction on the Canadian boreal plain occurs on woodland and/o r agricultural fields, but soil recovery from its impact is not well docume nted. Therefore, we quantified changes over 3 yr (1992 to 1994) in the chem ical properties of two Grey soils and the physical properties of a Grey soi l that were subjected to pipeline burial and cropped to barley. The pipelin e right-of-way (RoW) was divided into three zones: a road (or work) area us ed for vehicular traffic, a trench area for burying pipeline, and a pile (o r spoil) area where soil was stockpiled during excavation. Pipeline constru ction resulted in mixing of subsoil material with topsoil, and the chemical properties most affected were those that varied most with depth. The pH, e lectrical conductivity, soluble sulphate, and exchangeable Ca and Na were i ncreased in the surface 20 cm of soil, particularly the road and trench are as. The affected properties moderated 2 or 3 yr after pipeline construction as soluble components were dissolved or dispersed and translocated back to lower soil depths. The RoW zones had increased soil strength and compactio n, and reduced water retention and infiltration rates. However, the deterio ration in soil physical condition was similar across the RoW zones, indicat ing that it was due mainly to land clearing, a requirement to convert woodl and to agricultural land. Improvement in bulk density, and water infiltrati on and retention in 1993 and 1994 indicated that the RoW was undergoing reh abilitation with time as a result of natural processes and annual cropping.