ИСТИНА

Lignin is one of the main components of plant litter (25 % of the dry of dry weight). But despite the significance described to lignin in the humus formation our knowledge on the really amount and degradation pathway of natural lignin in the different zonal soils of Russia is rather fragmentary. Such characteristics of soil organic matter as content and composition of aromatic lignin acids and aldehydes have never determined in them. It was established, that the main source of lignin in ecosystems studied are wood and plant roots (table 1). Actually, the content of lignin-derivated products strongly correlates with the amount of plant roots in soils under subalpine meadow (coefficient of correlation is 0,92) and alpine meadow (0,93), as well as under the juniper’s forest (0,99). Sum of lignin-oxidative products in the soils studied reflects different biochemical conditions of humification (Table 2). The alpine- meadow Leptosols Umbric shows a decrease of VSC from 82,28 mg/g Corg in the OA horizon to about 1,12 – in the humus horizon. Gleysols Mollic of Moscow region are characterized by the highest content of the aromatic lignin structures (to 16 mg/g Corg) in the humus horizon. The degree of side-chain alteration of the lignin molecules in it is also lower – 1-2 %. That is way the role of humic acids abiotic condensation from simple free monomers is more considerable in lowlands hydromorphic conditions and in high mountain soils, where microbial activity is more lower and ferment amounts is also low. High-molecule compounds preserve and gradually change into humic acids by the way of biopolymer degradation, the degree of lignin molecule oxidation increases. The steppe type of accumulation and profile distribution of lignin-derived phenol compounds is characterized by low lignin content in the A horizon (0,66 mg/g Corg). VSC increases gradually along the profile of Chernozem from 0,66 mg/g Corg in the humus horizon to about 1,16-2,12 mg/g Corg in the AB horizon and can be explained by the input of root litter. The degree of side-chain alteration of the lignin molecules - to 22% in A horizon and to the 53 % on the 40-60 cm in buried middle Holocene humus horizon (Ab). That is way, in Chernozems, as in soils with high biochemical activity the more possible pathway of humification is the deep and quick fermentative degradation of high-molecular compounds to the monomers. The ratio (asids/aldehyde)v, what is the measure for the degree of side-chain alteration in the lignin remnant molecule in the Chernozems is about 0,59 in comparison to 0,24–0,29 in hydromorphic Greyzems Haplic and Gleysols Mollic. In the alpine Leptosols Umbric the (asids/aldehyde)v ratio is about 0,54 with a distinct minimum in the intensively rooted horizon – 0,29, - produced by fresh root litter material. The S/V ratio in Chernozem profile increases from 0,51 in A horizon to 0,63 – in B. This fact reflects the degradation of siringyl alcohol-derived structures over coniferyl alcohol-derived structures. Actually, the C/V ratio in Chernozem decreases with depth from 1,68 in humus horizon to 0,14-0,20 – in AB and B horizons. The C/F ratio also decreases from 1,9 in A to 0,85 – in B horizon. These dates are result from high amount of coumaryl structures in remnant of grasses tissues. Due to the biochemical specificity and high sustainability of plant lignin compounds it can be used as a molecular traces of terrestrial plants in the paleolandscape studies . Actually, proportions of syringic, vanillic and p-coumaric structures in organic matter of the arable Greyzems Haplic reflect the genesis of plant residues: grasses root litter in the plouth horizons – 1:2:1, leaves tissues at the depth 40-60 cm (buried humus horizon) – 6:5:1. This fact is the relict property of the forest genesis of these soils.