Fractional composition of humus compounds in the ectohumus of soils in the Galio Sylvatici-Carpinetum and Alno-Ulmion forests

The aim of the study was to analyze the fractional composition of humic compounds in ectohumus O and humus A soil horizons in two forest associations: Galio Sylvatici-Carpinetum and Alno-Ulmion in relation to chosen physical-chemical properties of soils. The following analyses were performed on collected soils samples: texture, pH in 1mol KCl dm -3 , exchangeable acidity, organic C, N total, the contents of exchangeable cations of alkaline character (Ca +2 , Mg +2 , K + , Na + ) and fractional composition of humic compounds using the Tiurin method. River alluvial brown soils were investigated. The soils were characterised by an acidic reaction and a typical distribution of organic matter with maximum content in the accumulative horizon. Fraction Ia (fulvic fraction, consisting of low compound fulvic acids, extracted with 0.05 mol dm -1 H2SO4) accounts for a rather insignificant part (1.14-7.11% C total) of humic compounds. Humus is dominated by fraction I (humic compounds bound with calcium and mobile forms of R2O3, extracted with 0.1 mol dm -1 NaOH). This fraction is significantly different and in the range from 9.14 to 49.68% C total; in turn the CHA/CFA ratio has a value between 0.69-2.59. Fraction II (humic compounds bound with the stable silicate forms of R2O3) is placed in the range 1.30-6.09% C total. Non hydrolyzing C constitutes 46.55-88.18% of C total.