ALUMINUM TOXICITY IN DECLINING FORESTS - A GENERAL OVERVIEW WITH A SEASONAL ASSESSMENT IN A SILVER FIR FOREST IN THE VOSGES MOUNTAINS (FRANCE)

A general overview on Al toxicity to plants is given, including the following aspects: symptoms; mechanisms; mitigating environmental factors; and diagnostic possibilities. An Al toxicity index is proposed to replace the classical but poorly performant Ca/Al ratio and is used in a declining fir stand in the Vosges mountains (eastern France). A potential Al toxicity phase was observed in winter only, namely during the vegetation rest phase. As nutrient uptake is expected to be potentially low during this season, this finding suggests that Al toxicity is probably not strongly involved in the local forest decline. However, a low influence may occur with respect to the winter growth of mycorrhized fine roots.