Soil Chemical Properties in a Tolerant Hardwood Ecosystem Response to Acid Deposition and Forest Harvesting.

The impact of declining inputs of atmospheric acids and clearcut forest harvesting on soil chemical properties was examined at the Turkey Lake Watershed (TLW) located on the Precambrian Shield in central Ontario, Canada. The TLW has been the site of multi-discipline ecosystem research since 1979. The 10.5 km² watershed is positioned in uneven-aged tolerant hardwood forest with 90% of the basal area as mature to over-mature sugar maple. Podzolic soils with mor organic horizons have developed in thin glacial till deposits over predominantly metamorphic silicate bedrock. A small headwater catchment (4.6 ha) was harvested in 1997 using a diameter limit cut in which all trees > 20 cm diameter were felled, de-limbed, and removed, and all trees 10-20 cm diameter were felled. Harvesting left 22% of the pre-harvest overstory volume as live standing. Reductions in S emissions during the past 35 years have resulted in declines in precipitation SO₄^- deposition in this region. Exchangeable cation concentrations of mineral soil horizons were determined in 1980, 1999, 2002 and 2015 to discern long-term changes in response to cation leaching, harvest removals and weathering inputs.