Impacts of forests on water chemistry

Abstract

Forest canopies and soil organic horizons have been identified as two major components of forest ecosystems interacting with and altering the chemistry of rainwater. Data, collected over a 13-yr period from different softwood and hardwood stands located in central New Brunswick, are presented to demonstrate differences among stands in their ability to alter the chemistry of rainwater. In both the canopies and the soil organic horizons, retention and exchange processes are effective in altering the chemistry of rainwater. Significant species effects are recognized in the partitioning of rainwater into throughfall, stemflow, and interception, and in altering of its chemistry. Stemflow components generally contribute to acidity, while throughfall reduces acidity of rainwater. Some of the chemical characteristics of rainwater reaching the forest floor are shown to be similar to those of streams associated with the forest stands. The data show significant species effects on the moisture retention characteristics of the organic materials accumulated under each stand, which in turn affect the residence time of the acid components of rain. Admittedly, before entering streams and lakes associated the composition of the liquid leaving the organic horizons is further altered by mineral soils.