Soils of erosion areas

The soils of South Estonian uplands vary greatly. This has been caused by rapid alteration of sediments of different size and origin (gravel, sand, varved clays, till of different types, peat), which, in turn, combine with dissected relief. Sparse growth of cultivated plants on arable lands and their weak root systems allows the precipitation to freely penetrate into the ground or flow down the slopes. As a result, the uppermost layers of soils together with nutrients necessary for plant growth are washed away from elevated areas. The topsoil gets thinner and poorer on hilltops and slopes. The eroded material accumulates at the foot of the slopes and in depressions, forming a thick (often as thick as 1 meter, sometimes even more) deluvial horizon.

Peculiar combinations of soil distribution can often be seen on soil maps. Eroded soils cover the tops and slopes of positive relief forms. Usually they are surrounded by concentric circles of deluvial soils, marking the foot of hills or ridges. The bottoms of the depressions are usually covered with Gleysols and Histosols. Such a pattern of soils is quite noticeablein spring, when the fields have been ploughed, but crops have not come up yet. Eroded soils can be distinguished as lighter or reddish patches, replaced by blackish brown ones in deluvial areas. The alternation of eroded and deluvial soils can also be noticed by the growth of crops — the vegetation is weaker on the upper parts of the hillocks, and lusher on the lower parts.

Heavy rainfalls cause the appearance of gullies on the hill slopes. A short but very heavy downpour cut a 1.2-meter-deep and 10 meter long gully into the southern slope of Vorstimägi. A small fan-shaped outwash, consisting of till, sand and gravel, was formed in its mouth. In natural landscapes a litter of natural vegetation prevents the erosion of soils even on very steep slopes.

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