Delineating Acidified Soils in the Jizera Mountains Region Using Fuzzy Classification

Abstract

Soil acidification represents a serious problem in mountainous areas of the Czech Republic. It is mainly caused by acid parent materials, high precipitation, the type of vegetation, and acid deposition. These factors act in different combinations and result in different soil conditions. The aim of this chapter is to distinguish areas in the Jizera Mountains with different levels of soil acidification and sensitivity using fuzzy classification. A set of 98 sampling sites was analysed and sampling density was approximately one site per 2 km2. Samples were collected from surface organic horizons (O), depth ranged from 4 to 22 cm depending on site conditions. Soil analysis included active and exchangeable soil pH, total content of C, N, and S, pseudototal content of Ca and Mg (after aqua regia digestion), and the ratio of absorbances of soil sodium pyrophosphate extract at the wavelengths of 400 and 600 nm as indicator of humus quality A400/A600). Moreover, concentrations of exchangeable Al in KCl extract and organically bound Al in Na4P2O7 extract were determined. Soil classes were calculated using fuzzy k-means method with extragrades. Five classes were selected. The first class with high exchangeable Al content, high S and N, and low Ca, represents the area that was most affected by the acid deposition. The second class with the lowest pH represents strongly acid soils that have very high sensitivity to acidification, but with smaller acid deposition. The third class with high Ca content includes the areas that were limed in the past. The fourth class includes principally the sites with the highest S and N deposition that are populated by grass. The fifth class includes the areas with high Mg content; its distribution corresponds to beech forests that have more favourable effects on soils than spruce forests. Fuzzy classification distinguished soils with strongest sensitivity to acidification. Positive effect of beech forest, grass cover, and liming on surface organic soil horizons is shown.