Research into forest decline and air pollution in France. Major findings and relevance for policy applications

Abstract

The Deforpa Programme (Forest Decline and Air Pollution) (1984-1991) aimed at identifying the causes of decline in conifers in the French mountains. The yellowing Norway spruce (Picea abies K.), which reveals a Mg deficiency, results primarily from the long-term acidification and cation depletion of originally poor soils under the influence of acid deposition and harvest. Other air pollution effects include stream acidification in the Vosges area and eutrophication of forest ground vegetation. Ozone effects remain uncertain. Climatic anomalies affecting vulnerable stands in relation with their history were found to be the main causes of silver fir (Abies alba Mill.) dieback. Despite these air pollution effects and visible damage, the productivity of the studied species has increased over the past century; the causes (climate change, increased N deposition and CO 2 levels, silviculture) are not yet identified. Critical loads are thought to be a valuable tool for defining further emissions abatements to protect the sensitive parts of the forest ecosystem (flora, soils, surface waters). © 1992 Elsevier Science Publishers B.V. All rights reserved.