Acid depositions, summer droughts, forest decline: Development of the nitrous acid hypothesis

Abstract

The author develops the nitrous acid hypothesis which could explain the triggering effect of drought on forest decline. The first rainfall after summer drought (FRAD) revivifies nitrifiers and so gives rise to an acidification push with nitric acid production. But also denitrifiers are rapidly revivified in anaerobic micro‐sites. During this climatic event, intermediate NO⁻ ₂ of nitrification‐denitrification (as undissociated HNO₂ species) would react arastically and without discrimination on dead and living organic matter, thus altering roots and mycorrhizas, particularly in the direct vicinity of aggregates.