Two of the most striking features of acid soils are their high exchangeable Al content and their low base cation status. Although acid soils have proved to be unsuitable for a number of agricultural species, most of them have till now allowed the development of forest ecosystems. The natural occurrence of soluble, organically complexed, Al has been recognized for many years in podzolic soils (Kononova 1961; Duchaufour 1970; David and Driscoll 1984; Dahlgren and Ugolini 1989). The existence of soluble inorganic Al in acid brown soils, mainly arising from acidification due to biological processes (nitrification, mineralization of organic sulphur), is a more recent observation (Ulrich et al. 1980; van Breemen et al. 1987; Nys 1987; Becquer 1991; Baur and Feger 1992). A number of tree species have adapted to such chemical conditions. Due to atmospheric pollution and related acid deposition, base cation content in soils and soil solutions has strongly decreased in the last decades in some areas (Falkengren-Grerup and Eriksson 1990; Hallbäcken 1992; Joslin et al. 1992), whereas concentrations of soluble Al have been assumed to increase. Moreover, important changes in Al spe-ciation are expected to occur in many acid ecosystems, with possible partial decomplexation of soluble organic Al due to pH decrease. Whether the vegetation will adapt to such environmental alterations is uncertain. The toxicity of soluble Al for many agricultural species is well known, most of them being sensitive to Ca deficiency as well (Foy 1988; Rengel 1992). More recently, it was hypothesized that either Al toxicity (Ulrich et al. 1980; Hüttermann and Ulrich 1984) or deficiencies in Mg or Ca (Zöttl and Hüttl 1986; Joslin et al. 1988) could also be involved in forest decline. Strong arguments in support of the occurrence of Mg x Al and Ca x Al interactions have been reported (Godbold et al. 1988; Joslin and Wolfe 1992; Schlegel et al. 1992).
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- Potential Role of Aluminium Toxicity in Nutrient Deficiencies as Related to Forest Decline: An Assessment of Soil Solution Data from the Vosges Mountains
D. A. Mohamed
- Springer Berlin Heidelberg