Traces of the windfall pedoturbations in the dark-humus (Haplic phaeozem) soil in the «Kaluzskie zaseki» reserve

We analyzed the morphological structure of the dark-humus (Haplic Phaeozem) soil in the old-growth oak forest massive located in South district of the Reserve «Kaluzskie zaseki» (Kaluga region, European part of Russia). The dark-humus soils occur relatively rare in the Reserve; they are situated inside vast areas of sod-podzolic and grey soils (Luvisols). The dark-humus soils are confined to areas of very erosive relief in the Reserve's South district, but one can find these soils in ravines' slopes and in flat areas (placors) as well. Typical dark-humus soils have a AU - C structure, where AU is a dark-humus horizon, and C is a soil-forming rock. The usual power of AU horizon in this soil doesn't exceed 30 cm. However, in the Reserve the power of the AU horizon in the dark-humus soils varies from 40 to 112 cm with the average 68.0±4.2 cm. The aim of our work was to investigate dark-humus soils morphology and to assess inputs of trees' windfalls in soil formation. Several long soil profiles (trenches) up to 6 meters were studied by means of the detailed morphological analysis at the levels of horizons and separate morphons. Traces of old trees' windfalls with uprooting were identified in almost all soil profiles. On the basis of the structure of the studied trenches, we marked two types of structure elements in the soil cover. The first one (we named this pedons) is good marked at the soil profile background; profiles' horizon structure is less complicated by windfall mosaics (by windfall poly-morphones) here. The second one is 'the limit structural elements'. They are marked in the profiles where profiles' horizon structure is greatly transformed by trees' windfalls with uprooting. We have shown that formation and destruction of trees' roots as well as trees' windfalls lead to the deepening of the lower boundaries of soil horizons. The depths of roots are similar for many forest tree species, so we can wait for the following: in a long-term forest area in a soil profile at least one horizon should be caused by the depth of trees' anchor roots and by the soil turning after tree falls with uprooting. Since root systems of trees deviated from the habit average parameters, there is one or two additional horizons with boundaries above and below the background. In the dark-humus soils in the «Kaluzhskie zaseki» Reserve, the depths of the humus horizon vary from 40 to 60 cm on typical sites. This depth is determined by the power of old windfalls and soil fauna activities. 'Non-typical' soils have mosaic profiles, the depths of the old windfalls in these soils range within 120-150 cm.

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