To develop the layer-by-layer express analysis for estimation of the elemental (Ca, Mg, etc.) content, the relationship between the spectral line relative intensities and Ca, Mg concentrations in water solutions has been studied using the method of laser spark spectroscopy providing probing of the surface and bulk of porous samples with dried salts by double laser pulses. The analytical methods for quantitative estimation of Ca and Mg concentrations have been developed. The layer content of Ca and Mg in rind samples of spruce stock in Minsk and Berezinski biosphere reserve has been analyzed.