35 Years of Soil Acidification Monitoring in Alberta, Canada.

In 1981 the Government of Alberta implemented a program to monitor soil acidification in response to concerns about acid rain that were then prominent in North America and Europe.  The program was intended to provide an early warning of soil chemical changes related to acid air emissions.  Eight sites were established on sandy soils across the Province in a range of natural regions, from shortgrass prairie in the south to boreal forest in the north.  The sites have been monitored since that time, with a short break in the mid-1990s, on a four year rotation (two sites per year).  A ninth site was added in 2008.  At each monitoring event, samples are taken by depth and analyzed for pH in CaCl₂ and soluble and extractable ions.  Ca:Al, base cation:Al, and base saturation are calculated.  Grassland sites, which have high base status, have shown little evidence of acidification. Boreal sites, which are more highly leached and tend to be naturally acidic, have shown evidence of acidification, although the changes in soil chemistry are not reflected in obvious vegetation changes.  Over the last 35 years the program has faced a number of challenges, including forest fires, third party disturbances, and changes in sampling personnel and laboratories.  Despite this, it has provided a useful picture of soil acidification trends that has been used to support regulatory policies for the management of acid air emissions.