Johnson, D.W., and M.J. Mitchell. 1998.
Chapter 16. Responses of forest
ecosystems to changing sulfur inputs. In: D. Maynard (ed.). Sulfur in the
Environment. Marcel Dekker, Inc. pp. 219-262.
Several studies have addressed the effects of increased S inputs in
forest soils and forest ecosystems but few have considered the effects of
decreased S inputs which are now occurring as S emissions decline in many
polluted regions. These decreases in S emission have been reflected in
decreases in SO42- concentrations of surface waters in the Northeast U.S.,
eastern Canada, and Europe; however, there are no data as to effects on
soils or forest ecosystems. The degree and duration of SO42- release from
organic matter, precipitates, and adsorption sites under lower deposition
will have profound impacts upon the effectiveness of S emission controls
on both terrestrial and aquatic ecosystems. We know little about the
potential release of S from organic matter under reduced S availability.
Models are available which can predict the release of SO42- from
precipitates and adsorption sites; however, none of the current models
incorporate the significant hysteresis always noted in the
adsorption-desorption of SO42- from soil adsorption sites.