ИСТИНА

The source of lignin phenols in soils are the lignocelluloses (70 to 90 % dry weight of plant tissues). Trees of the Nordic ecosystems contain the highest lignin amount, but they did not play the important role in humus formation. The aim of this work was a detailed characterization of the lignin phenols composition and processes of their transformation in soils of the secondary forest. The objects of investigation were Gray soils of the southern taiga (Russia). An experimental plots (600 m2) with the different types of trees (spruce, birch, pine, aspen, larch, cedar) was created in 1971-1972 (the soil samples were provided by Prof. W. Zech). The grassland (1400 m2) was left as a control. The process of lignin determination in the soils included the alkaline oxidation of a sample using copper oxide at 170°under the pressure in a nitrogen medium. The lignin phenols were divided by a gas-liquid chromatograph. The isolation of lignin oxidation products from the litters of different plant associations showed, that their lignin parameters were similar, but less contrasting than those in plant tissues. The highest content of lignin was found in the spruce forest litter. The composition of the coniferous litters (spruce, fir, pine, larch) was characterized by the accumulation of vanillic phenols and retained tendency toward a decrease in the content of syringic and coumaric structures. The deciduous forest litter (birch, aspen) contained similar proportions of vanillic and syringic phenols and a lower content of ferulic acids. Cinnamic phenols predominate among the lignin phenols of the grass community in the control plot. The presence of cinnamic phenols in the composition of soil lignin in trees ecosystems indicates that 50 years was insufficient for the transformation the difficulty decomposable grass lignin.