Bavarian Forest
National Park

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Geology and Soils

Bear Cave Rock (Photo: Rainer Pöhlmann)

Geology

The Bavarian Forest National Park is located on the south western edge of the largest basement in central Europe, the so-called Bohemian massif. These very old rock formations are more than 280 million years old, and composed primarily of gneiss and granite.

Various gneissic rocks – mainly cordierite, sillimanite and biotite-plagioclase gneiss – cover the largest part of the national park territory. Only around the Lusen massif is there a large granite area, composed of Finsterau crystal granite. In addition there are small deposits of rarer rocks distributed over the area such as serpentinite, amphibolites, redwitzite-metabasite, lime silicate and transitional forms of gneiss and granite, pegmatite, aplite and quartz veins.

Today’s landscape was shaped decisively during the ice ages. The corrie wall and basin of the Rachelsee and three paludified lakes from the ice age point to the presence of small glaciers. Clear traces of moraine can be found on the south east and northern side of the Rachel mountain, in the Schwarzbach valley as well as beneath the so-called crypt (Gruft) to the north east of Buchenau. The stone blocks of the Lusen summit were most probably created during an almost snow-free and dry continental phase of the ice age influenced by frost-shattering.

Solifluction in glacial permafrost soils led on the lower hillsides to fine earth rich, mighty soil strata, whilst on the upper hillsides imposing rock formations and boulder fields appeared as a result of the run off of the fine soil. The processes of solifluction are also the apparent cause of the accumulation of glacial scree, ecologically important for the landscape, and typical of the soils of the high areas and upper slopes of the inner Bavarian Forest.

In the post ice age thaw powerful water masses transported scree to the valleys that today thickly covers the bottoms of the streams in the area.

Soils

Soils in the Bavarian Forest National Park are weathering products of gneiss and granite. These acidic primary rocks weather only very slowly and possess only very small amounts of important plant nutrients such as potassium, calcium and magnesium. The soils of the national park are thus naturally acidic and low in nutrients.

The most common types of soil in the national park area are brown forest soils, loose brown soils, podsols, gleys and peat soils of varying forms.

Brown soils are the predominant type of soil in the lower slopes. They consist mostly of fresh, primarily sandy, deep weathered loam with, as a rule, a small portion of skeletal soil and modest to moderate nutrient supply. In the area of the mid and upper slopes – from 900 metres above sea level – they are increasingly mixed with loose brown soils, which are characterised by a large looseness of the soil fabric owing to a high total soil porosity and a high humus content.

In the high areas brown soil or podsol brown soil predominate on loam of intermediate to great depth over consolidated scree, which on the plateaus are more distinct as iron humus podsoils. The upper border for the growth of beech trees can be found between 1100 and 1200m above sea level, dependent on aspect, which as a rule coincides with the meeting point of the loose brown soils of the upper hillsides and the poorer high area soils on consolidated scree.

Rock and boulder soils are widespread in the higher and in summit areas as well as in places across the whole area. Gley soils with their high groundwater content are widespread in the waterlogged valley areas, close to springs and along streams. If groundwater is present up to ground level then mires are formed. Fens and transitional bogs can be found across large areas in the mire forests of the valleys and over small areas in the hillsides as spring mires. In the high areas and the valleys of the national park impressive raised bogs have formed (Großer Filz, Klosterfilz, Zwieseler Filz). These arise when the peat bodies outgrow the influence of the groundwater and form their own bodies of water fed by rainwater.