Impact of Declining S Deposition and Harvesting On Carbon and Nutrient Leaching From Contrasting Forest and Soil Types.

The impact of declining inputs of atmospheric acids and vegetation removal during forest harvesting on soil chemical leaching was examined for differing forest and soil types in north-eastern Ontario, Canada. Study sites included the Turkey Lake Watershed, a mature sugar maple dominated tolerant hardwood forest with shallow glacial till soils; Wells LTSP (Long-Term Soil Productivity) site, a fire origin jack pine forest with deep glaciofluvial soils; and the Esker Lakes Research Area, a fire origin spruce forest with finer textured soils developed in the glaciolacustrine deposits. Reductions in S emissions during the past 25 years have resulted in declines in precipitation sulfate deposition in this region. Harvesting treatments included clearcut, selection and shelterwood systems at the Turkey Lake site, full-tree and full-tree and organic matter removal by blading at Wells LTSP and full-tree at the Esker Lakes Research Area. Soil percolate sampled using zero-tension and tension lysimeters was analyzed for major ions, nutrients and carbon. Soils exhibited a large range in soil base content, natural production of nitrate, and adsorbed sulfate that influenced response to changes in anthropogenic deposition and harvesting disturbance.