Abilities of organic horizons under some eastern Canadian forest stands to alter the acidity of rainwater

Abstract

Various precipitation data, collected over a 13-year period, from different softwood and hardwood stands located at the Acadia Forest Experiment Station in central New Brunswick are evaluated to demonstrate differences between stands in their ability to alter the acidity of rainwater. In the soil organic horizons, retention and exchange processes are shown to be effective in altering the acidity of rainwater. Significant species effects in the quantities of water retained by the organic horizons are recognizable owing to differences in the quantities of organic materials accumulated under each stand and their moisture-retention characteristics. In turn, differences in the quantities of liquid retained in the organic horizons affect the residence time of the acid components of rain reaching the mineral soil. Major differences in chemical characteristics such as cation-exchange capacity, percent base saturation, and pH of the organic horizons suggest that the interactions of acid components of wet and dry deposition of air pollutants can be significantly different depending upon the species composition of stands.