Abstracts

Soil Ecosystems

In the Northern part of Siberia the depth of summer soil thawing is the main factor, which predetermines the whole complex of ecological conditions as well as the look, structure and formation biogeocoenoses (Sofronov, Volokitina, 1998). Therefore it is very important to measure the depth of soil thawing in that region making use of a method, which takes into account an ecological role of thawing.

The majority of meteorological stations carry out observations of the course of soil thawing and freezing. The depth of thawing is measured from the surface of soil (Dimo, 1972). It should be noted, that in the Northern part of Siberia typical vegetation formations have a surface floor covered with a continuous layer of moss and lichen. When studying these formations, the depth of soil thawing is usually measured from the surface of a moss-lichen floor. This method is doubtful from the point of view of soil-scientists and ecologists.

Firstly, a live moss-lichen floor must not be identified with the upper soil layers, thereupon it can't be summarized together with a thawed out soil layer.
Secondly, there is no ecological similarity (according to temperature regime and depth of rooted layer of soil) on the plots: 1) with moss floor; and 2) without moss floor - by the same depth of soil thawing.

On the plots without moss floor and developed duff the depth of rooted layer of soil is almost identical to the soil layer (mineral) thawed out by the end of summer, since roots of grasses and sedges are situated near the soil surface, and separate live roots are met even in frozen earth (Dadikin, 1952). 

On the plots with developed moss floor there are no plant roots in the upper live moss layer (layer 01). Roots are almost never met also in the second layer composed of died off moss stems (layer 02). But there is a great number of roots in the third organic layer composed of humus and peat (layer 03).

Consequently, the depth of rooted layer of soil on the plots with moss floor consists of 1) a low part of organic soil layer (layer 03 of duff) and 2) an upper part of mineral soil layer thawing out by the end of summer.

It is desirable to elaborate such a method of depth soil thawing evaluation that reflects ecological importance of the depth of soil thawing for vegetation in the Northern part of Siberia. Therefore the depth of summer soil thawing on the plots with moss floor is suggested to evaluate as a possible depth of rooted layer of soil, i. e. as a sum of: 1) depth of mineral soil thawing and 2) depth of low duff layer, penetrated with roots (layer 03).

Note. Abstracts are published in author's edition

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