Today’s gently rolling ground moraine landscape at the DEMMIN test site was formed primarily during the Weichsel glaciation. Examples are the glacial drift clays and marls of the ground moraines and the sands and fine gravel of the outwash plains.
Glacial advance and retreat in response to the alternate warm and cold phases of the Weichsel glaciation led to the formation of features like the terrain compressions resembling terminal moraines northwest of Malchin and the gently rolling hills in the northern approaches to the Pomeranian terminal moraines (Müller et al., 2002). The chalky glacial drift marls deposited during the Mecklenburg stage were in some places covered with a layer of glacial drift sand (Helbig, 1999a; Helbig, 1999b).
The Weichsel glaciation ended with the inception of Holocene warming 10,000 to 12,000 years ago. The melting of the glaciers gave rise to the well-known sequence of flat, undulating and hilly ground moraines; hilly end moraines; outwash plains and narrow outwash channels; glacial meltwater valleys and sand plain basins. The warming resulted in rapid melting of the glaciers.
The massive amounts of liberated meltwater drained through glacier crevasses under the ice. This led to the formation of new subglacial tunnel valleys or the widening of already existing older subglacial channels through the force of the outflowing meltwater (Cheung, Grünbauer, 1994). As the glaciers melted and retreated northward they left behind blocks of dead ice that gave rise to a system of shallow depressions and deeper hollows (Peterss et al., 2003).
During the Atlantic period (ca 8000 to 5000 years ago) marine transgression caused a rapid rise in the level of the Baltic Sea (Kliewe, Jahnke, 1982). The result was a backing up of water into the river valleys far inland. The ensuing reduction in flow velocity led to the settling out of fine sands and the formation of deep moors in the glacial valleys of the Peene, Tollense and Trebel (Müller et al., 2002).
In addition to the geological structures of the Weichsel glaciation, older geological landscape formations can also be identified near the Tollense valley and Lake Tollense (with characteristics of the Saale, Elster and pre-Elster ice ages) (Bremer, 2000). Examples are sands in or under the ground moraines, chalk massifs, and older intrusions.
The geological record described above explains why the existing soils are relatively young and hardly affected by erosion, acidification and shifting processes. The soil substrates are dominated by clay sands and sandy clays alternating with enclosed pockets of sand or stretches of clay. The north-eastern part of the test site typically has sandy brown earth and glacial sediment sands not under the influence of water. It is bordered by the ground moraines of the Western Pomeranian clay plains. Figure 1 gives the percentage distribution of soil types cultivated by the Demmin Network.
Because of the composition of the substrate and the good supply of nutrients and carbonate minerals the soil quality index of the soils is ≥ 40. The most important German soil groupings include Tieflehm-Fahlerde/Parabraunerde-Pseudogley (Braunstaugley), Tieflehm-/Sand-Gley/Pseudogley (Amphiegley), Sand-/Tieflehm Braunerde-Podsol (Braunerde), Tieflehm-/Lehm-Parabraunerde, Fahlerde/Pseudogley/Staugley. In many areas the ground moraines are affected to various extents by the influence of groundwater or backwater. In some places the ground moraines are hardly influenced by groundwater. The terrain is in many areas flat to gently rolling or rolling, and in some areas flat to gently rolling hilly to hummocky.
In the “Upper Peene Area” subzone the following soil groupings are to be found on top of the glacial drift marl (German classification): Lehm-/Tieflehm-Pseudogley (Staugley)/Parabraunerde-Pseudogley (Braunstaugley)/Gley (Amphiegley), Sand-/Tieflehm-/Lehm-Braunerde (Bänderbraunerde)/Fahlerde Parabraunerde-Pseudo¬gley (Braunstaugley), Tieflehm-Fahlerde/Parabraunerde-Pseudogley (Braunstaugley). The ground moraines (in some cases including the carved valley borders) can be either highly or moderately influenced by backup water and/or moderately to slightly influenced by groundwater. In addition, Sand-Braunerde-Regosol (Braunranker)/Podsol is common in the area. The terrain is flat to hummocky.
The ground moraines in the “Upper Tollense Area” subzone of the “Hilly Region of the Mecklenburg Lake District” landscape zone are dominated by such soil groupings as (German classification): Lehm-/Ton-/Schluff-Pseudogley (Staugley)/Gley-Pseudogley (Amphiegley), Tieflehm-/Lehm-Parabraunerde-Pseudogley (Braunstaugley)/Pseudogley (Staugley)/Gley, Tieflehm-Fahlerde/Parabraunerde-Pseudogley (Braunstaugley) and Lehm-/Tieflehm- Pseudogley (Staugley), Parabraunerde-Pseudogley (Braunstaugley), Gley (Amphiegley). These locations are moderately to strongly influenced by backup water or moderately by groundwater. The topography is flat to rolling and sometimes hummocky.
In all three subzones there are, in addition to the above-mentioned geological formations along the rivers, deep lowland moors (formed in the Holocene). Especially in the valley networks (for example, the Peene, Tollense and Trebel) throughout the ground moraine plains there were optimal conditions for the emergence of large percolation mires. In the 1920s land improvement measures led to the loss of vegetation communities typical of undrained percolation moors. In the 1980s the only remnants of the original vegetation were to be found in some of the old peat hand-harvesting sites in the Peene valley, including the Amblystegiaceae family of Hypnales mosses and Schoenus genus sedges (Succow, Jeschke, 1986). The most common soil groupings here are (German designations): Erdniedermoor (Erdfen)/Mulmniedermoor (Mulm), lowland moor peat on top of gyttja, or mineral sediments affected by groundwater or, after degradation, by backup water.
The test site has in general a gently rolling terrain with hilly areas along the Peene, Tollense, Trebel and Augraben valleys and near the terminal moraines. The altitude differences average about 50 m with up to 12° slopes in the southern part of the test site along the Tollense. Figure. 2 gives an impression of the landscape.
From left to right the photo shows an altitude profile looking from southwest to northeast near Buchholz along a visual axis at right angles to the Tollense valley.
The altitude profile illustrates the different topography of the landscape zones. While the southern part of the test site has elevations up to 80 m above sea level, the elevation in the clearly more level northern parts is only some 20 m above sea level. It can also be noted that the river bed of the Tollense is only a few meters above sea level in this area.
Bremer, F. (2000): Quartärgeologische Strukturkarte von MV - zusammengestellt unter Berücksichtigung des geologischen Kartenmaterials, insbesondere Schulz, W. (1976) von Bremer, F., Geologisches Landesamt, Schwerin 1994, ergänzt 2000.
Cheung, T., Grünbauer, G. (1994): Geobotanische Gebietsanalyse des Naturschutzgebietes Anklamer Stadtbruch (Mecklenburg-Vorpommern). Dipl.-Arbeit Botanisches Institut, Universität Greifswald.
Helbig, H. (1999a): Die spätglaziale und holozäne Überprägung der Grundmoränenplatten in Vorpommern.- Greifswalder Geographische Arbeiten 17, Greifswald.- S. 110.
Helbig, H. (1999b): Die periglaziale Überprägung der Grundmoränenplatten in Vorpommern.- Petermanns Geogr. Mitteilungen, Gotha.- 143(5/6).- S. 373 - 386.
Kliewe, H., Jahnke, W. (1982): Der holozäne Wasserspiegelanstieg der Ostsee im nordöstlichen Küstengebiet der DDR. Petermanns Geogr. Mitt., 126, 65-74, 1982.
Müller, U., Hammer, J., Bremer, F. (2002): Mecklengurg-Vorpommern.- In: Quartäre Sedimente als Geologische Barrieren.- Handbuch zur Erkundung des Untergrundes von Deponien und Altlasten, Bd. 9.- Hrsg.: Hammer, J. (LUNG, Landesamt für Umwelt, Naturschutz und Geologie Mecklenburg-Vorpommern).- Springer Verlag, Berlin.- S. 500.
Peterss, K., Ratzke, U., Strahl, J. (2003): Geologie von Söllen bei Rosenow, Landkreis Demmin (Teil II). - Neubrandenburger Geol. Beitr. 3, S. 113-120.
Succow, M., Jeschke, L. (1986): Moore in der Landschaft – Entstehung, Haushalt, Lebewelt, Verbreitung, Nutzung und Erhaltung der Moore.- URANIA Verlag Leipzig, Jena, Berlin.- S. 268.