Effect of liming on fine root cation exchange sites of oak

Abstract

Nutrient acquisition has been shown to be related to the root cation exchange capacity of roots (root‐CEC). Here, the effects of root‐age and liming or gypsum treatments on root‐CEC of fine roots of sessile oak [Quercus petraea. (M.) Liebl.] were studied. In the field, sampling was carried out one to five years, and in rootboxes 3.5 months, after the treatments. Root‐CEC was determined by an adapted desorption method based on percolation with 10⁻² NCuSO₄. The results showed that the root‐CEC was higher in young whitish roots than in older brownish roots, mainly as a result of higher concentrations of potassium (K). Liming or gypsum applications increased relative occupation by calcium (Ca) of root‐CEC and Ca/aluminum (Al) molar ratio, while decreasing relative occupation of Al (all significant at P<0.05), and this was true for older brownish roots and in the field, but not for young whitish roots. This indicates that the potential of fine roots for uptake of base cations, decreasing with root age in the control, could be maintained or increased after liming or gypsum treatments. Both treatments acted against ‘age’, so that for a given root‐age the roots of the liming or gypsum treatment were in fact ‘chemically’ younger than those of the control. The results support other results on fine root turnover, fine root mortality, tree growth, and foliar nutrition, and suggest that liming and gypsum enhanced root function, perhaps by extending the effective uptake lifetime.