Data on the molecular structure of humic substances (HSs) of zonal soils for the southern, middle, northern taiga and southern tundra of northeastern European Russia have been obtained. This was accomplished using solid-state 13C nuclear magnetic resonance (13C NMR) technique. The soils under study vary in the point of genesis and degree of hydromorphism. The impact of environmental factors (temperature and humidity) on qualitative and quantitative composition of humic (HAs) and fulvic acids (FAs) has been determined. Excess moisture significantly affects HS accumulation and HS molecular structure: hydromorphic taiga soils accumulate HSs enriched by unoxidized aliphatic fragments, tundra soils – the ones enriched by carbohydrate fragments. Various conditions of soil genesis predefine the specific character of structural and functional parameters of HSs in the southern taiga to southern tundra soils, as is expressed through the increased portion of labile carbohydrate and amino acid fragments and methoxyl groups within the structure of HSs. The tundra humification is characterized by levelling-off of structural and functional parameters of major classes of specific organic compounds of soils – HAs and FAs.

Soils of Russian European North were investigated in terms of stability and quality of organic matter as well as in terms of soils organic matter elemental composi-tion. Therefore, soil humic acids (HAs), extracted from soils of different natural zones of Russian North-East were studied to characterize the degree of soil organic matter stabilization along a zonal gradient. HAs were extracted from soil of different zonal environments of the Komi Republic: south, middle and north taiga as well as south tundra. Data on elemental composition of humic acids and fulvic acids (FAs) extracted from different soil types were obtained to assess humus formation mechanisms in the soils of taiga and tundra of the European North-East of Russia. The specificity of HAs elemental composition are discussed in relation to environmental conditions. The higher moisture degree of taiga soils results in the higher H/C ratio in humic substances. This reflects the reduced microbiologic activity in Albeluvisols sods and subsequent conser-vation of carbohydrate and amino acid fragments in HAs. HAs of tundra soils, shows the H/C values decreasing within the depth of the soils, which reflects increasing of aromatic compounds in HA structure of mineral soil horizons. FAs were more oxidized and contains less carbon while compared with the HAs. Humic acids, extracted from soil of different polar and boreal environments differ in terms of elemental composition winch reflects the climatic and hydrological regimes of humification.

A total of 212 soil profiles were described and assessed for physical and chemical properties during July 2006 as part of an Ecological Land Classification study along the Churchill River in central Labrador. Two major soil types were found in the study area along the Churchill River: Podzols and Organic soils. Podzolic soils covered approximately 60% and Organic soils occurred in 24% of the study area. Approximately 15% of the study area was classified as rock and other unconsolidated material. Summary results and a sub−set of the following soil units (from 10 soil profiles) are presented here and were distinguished according to the Canadian System of Soil Classification (CSSC) (Soil Classification Working Group 1998): Orthic Humo−Ferric Podzol, Placic Ferro−Humic Podzol, Gleyed Humo−Ferric Podzol, Sombric Humo−Ferric Podzol, Gleyed Regosol and Orthic Luvic Gleysol. The basic properties of the soil units identified above included: (i) morpho− logical descriptions of soil profiles with differentiated horizons; (ii) field−texture tests were used to determine classes and physical properties of sands, silts, loams and occurrence of mottles; and (iii) a range of soil chemical composition of different horizons ( e.g. , pH, total organic carbon [TOC] and select metal concentrations) which indicated no anthropogenic contamination above background concentrations in the area.