An application of the tracked vehicles in relation to a development of new gas- and oilfields resulted in greater loads on a tundra soil cover of the Yamal Peninsula. Studies of the morphological, physical, and chemical properties of the native and vehicle-disturbed soils were carried out in order to evaluate a susceptibility of tundra soil cover to different mechanical impacts.
A disturbance of native microrelief and a formation of ruts resulted in a greater flows of additional of volumes of water to the disturbed plots. The vehicle- induced mixing of the upper organogenic and lower mineral horizons caused a formation of new organomineral horizons which are not peculiar to the native tundra soils. These changes in conditions of soil formation affected the above-mentioned properties of soils.
In the surface horizons of tundra-gley soils, a specific surface area and a saturation water capacity declined from 111-227 to 37-68 m2 g-1 and from 1,33-2,41 to 0,44-0,88 g g-1, respectively, but bulk density rose from 0,31-0,51 to 0,36-0,76 g cm-3 after 4 passages of tracked vehicles. A close contact of mineral and organic constituents in the organomineral horizons led to a quicker and more complete humification of plant residues. The organic compounds formed in this way moved to mineral horizons and did not interact with mineral soil particles. A strong positive correlation of organic matter content with water retention of the disturbed soils (r = 0,81-0,99) compared to a poor correlation between these parameters of the native soils (r = 0,14-0,45) indicated a hydrophilic nature of the organic compounds formed. These organic compounds in soil solutions moved downward within a soil profile and a landscape. Then the organic compounds participated in leaching and redistribution of nutrients.
In the ruts, the fragile, round aggregates of the native tundra soils disturbed by tracked vehicles had no recovery in the upper horizons for four years. However, in the waterlogged organomineral horizons, there were laminar and platy micropeds separated by horizontal pore-cracks. Analogous structure was observed in the soils of spots. A transport of water and organic substances to the compacted horizons of the disturbed soils resulted in a contribution of processes of gley formation in the upper part of soil profile.
Differences in properties of the native and disturbed soils were defined by initial bulk density, number of passages, degree of gleying, depth of organogenic horizons, type of soil, and its location on a relief. Among the soils studied, the least changes in soil properties were observed in the tundra peaty-gley soils. The tundra-gley soils on flat plots showed the highest susceptibility to the mechanical impacts of tracked vehicles.
M. Sc. Natalya P. Buchkina Agrophysical Research Institute 14 Grazhdansky prospect St. Petersburg 195220 RUSSIA Telephone: (812) 534-4621 E-mail: ivl@agrophys.spb.su