Natural Regions in the Ilm district
The landscape of the Ilm district is characterized by five extensive types of natural regions that offer varying living conditions to all animal and plant species.
Ilm-Saale-Ohrdruf Muschelkalk Plateau
In the southeast, the Thuringian Keuper Basin is bordered by the Ilm-Saale and Ohrdruf Muschkalk Plateaus including the Reinsbergscholle, the Gosseler Plateau and the Ohrdruf Plateau (300 - 605 m above sea level). The Thuringian Basin belongs to the Triassic period in which horizontal beds of mainly Bunter sandstone and Muschelkalk were laid down. It is assumed that a lateral shifting of the river Gera is responsible for the fact that water of the Wilde Gera (one of the two head streams of the river Gera) is drained to greater depth and is leaching gesso and salt deposits in the substratum.
The landscape is characterized by rockslides, especially in the Plauesche Grund and the Kleinbreitenbacher Kessel. The slopes and screes with its mosaic-like structures exposed to the southwest are the habitat of many sub-Mediterranean plant species. The Muschelkalk plateaus are habitat of many important biotope structures with a large abundance of different species such as sub-Mediterranean xerothermous lawn with a variety of orchids, sagebrush steppes, meadows with scattered fruit trees, etc. For protecting orchids calcareous low-nutrient meadow complexes as well as oak and pine tree forests are of great importance. Coppice rich in species can only be preserved by continuation of extensive farming.
Valley heads emerge where the lower Muschelkalk merges into the upper Bunter sandstone which is lying underneath it. That way spring fens developed that are of great significance for rare plant communities with various orchid species. Since a couple of years these low-moor bogs are mown only once so that they could be preserved with a large abundance of different species.
Inner Thurigian Arable Downs
The inner Thuringian arable downs of the Thuringian Keuper Basin (200 - 300 m above sea level) north of the district capital are being utilized mainly agriculturally. In the last couple of decades, most of the nearly natural features of the landscape fell victim to an intensification of agricultural production. Only a couple of them could be saved, such as oak-beech-mixed forests and sub continental dry grasslands in the area of the three castles Drei Gleichen which are important habitat complexes for many endangered animal and plant species. Especially scrub encroachment and reforestation can only be counteracted by extensive shepherding and specific cultivation.
Middle Thuringian Forest
The southern areas of the Ilm-Kreis with their Paleozoic sediment and effusion rocks form part of the arboreous middle Thuringian Forest (up to 983 m above sea level). Apart from only little remains of nearly natural mixed forests with single firs, mountain meadows rich in species are one of the most valuable habitat complexes. They mainly consist of nard grass, yellow oat grasslands or rather globeflower-knotgrass meadows and are of significant supraregional importance because of their abundance of different species.
Paulinzella Bunter Sandstone Forestland
The Paulinzella Bunter sandstone forestland (200 - 600 m above sea level) is located southeast of the Muschelkalk landscape. It is mostly an agricultural and silvicultural area where ponds, sloughs and wetlands populated with peat-bogs developed because of brick clay retaining the water in that area. On the dry sandy soils one can find pine and spruce forests with small shrubs growing underneath the trees. Also interesting are partly small and therefore very sensitive biotopes located above remains of Bunter sandstone and Permian in the northern Thuringian Forest. In the high altitude areas of the Thuringian Forest one can find most of the Thuringian hill moors. Those hideaways of seldom plant and animal species are proof for postglacial development of forests and hill moors.
The geologic faults at the mountain Langer Berg near the town Gehren make visible the shift from red porphyry to the rock layers of the Thuringian Shale Mountains. The Schwarza-Sormitz area starts northwest of the Schwarzburger Sattel. In the northern part of the western Thuringian Shale Mountains near Gehren extremely narrow and deep valleys of the river Schwarza attract ones attention.