Diving leaf zone
The diving blade zone (also diving blade belt) is one of the shore zones of lakes and other inland waters . It follows in the bank zone, technically called littoral , to the deeper water on the floating leaf zone and the reed belt . The diving leaf zone is part of the sublittoral, the lowest area of the illuminated littoral at the transition to the lightless profundal .
In Central Europe, spawning herbs are the dominant group of plants in the diving leaf zones in freshwater. They give the plant sociological group (after Oberdorfer) the underwater spawning herb communities. Other groups that occur are, for example, mermaid herbs ( Najas ), milfoil ( Myriophyllum ) or waterweed ( Elodea ).
Very similar forms of vegetation can also be found in quiet sections of slowly flowing rivers and other flowing waters.
The aquatic plants of the dip sheet zone live immersed ( submerged ). The stems and leaves are carried by the water. They only have a very thin cuticle, no protection against evaporation, and they also have no stabilizing tissue . The roots are only used for anchoring. Underwater leaves have no stomata so that gas exchange takes place over the entire leaf. The leaves are often very small and ragged. This creates a larger surface in a small space, through which the minerals and carbon dioxide are absorbed. The plant species of the diving leaf zone belong to the aquatic (that is, living in water) macrophytes; These are differentiated from the algae species, which are often only recognizable microscopically, on the basis of purely pragmatic aspects, whereby the large chandelier algae are usually counted among the macrophytes. When structuring the vegetation of the waters, the macrophytes and the (other) algae are usually examined separately; the algae species of the diving leaf zone are not taken into account in the vegetation breakdown. Macrophytes in the diving leaf zone are therefore predominantly herbaceous vascular plants, rarely also mosses (such as spring moss ) and chandelier algae. The species of the diving leaf zone form the subgroup of the submersed (that is: living submerged), rooting macrophytes (rarely referred to as rhizophytes). Helophytes (or marsh plants) and floating leaf plants rooted in the water bed are missing due to the depth of the water. Where floating leaf plants occur, they can compete with diving leaf plants through shading and thus displace them. In very nutrient-poor (oligotrophic) waters, in which floating leaf plants are almost completely absent, diving leaf plants can penetrate into the actual bank belt. In extremely nutrient-rich (hypertrophic) waters, there is no diving leaf zone, here the water is usually so clouded by phytoplankton that the submerged aquatic plants no longer receive enough light.
Vegetation and plant-sociological classification
The species composition of the vegetation of the diving leaf zone is related to the often immediately adjacent floating leaf zone. Both are summarized in the plant sociology in the class Potamogetonetea and therein the order Potamogetonetalia. Since the names of these societies are difficult to pronounce, they are often abbreviated somewhat: Potametea, Potametalia; for associations Potamion instead of Potamogetonion, for associations Potametum instead of Potamogetonetum; although the abbreviated spelling is actually incorrect according to the nomenclature rules, both spelling variants are in use.
The vegetation of the diving leaf zone is usually relatively poor in species, the species that occur then tend to dominate or even single species. The vegetation differs in nutrient-rich (eutrophic) and nutrient-poor (oligotrophic) waters. These can be distinguished by the growth habit of the predominant species of pondweed (of the genus Potamogetum ). While broad-leaved spawn herb species (the so-called large spawning herbs) predominate in eutrophic waters, narrow-leaved so-called small spawning herbs predominate in oligotrophic waters.
Great spawn dive corridors
The large spawning corridors of the nutrient-rich waters form the association Magno-Potamogetonion (from the Latin magnus: large) in the plant-sociological system . Under the (abbreviated, see above) name Magnopotamion , natural eutrophic lakes with vegetation of the Magnopotamion type (and / or the hydrocharition belonging to the floating leaf zone) are protected habitat type (code number 3150) within the framework of the European Natura 2000 protected area system .
Distinguishing species ( character species and differential species ) in northern Germany are Spiny Laichkraut Potamogeton friesii , Streaky Laichkraut Potamogeton perfoliatus , Spreading water crowfoot Ranunculus circinatus , Spring moss Fontinalis antipyretica , Crested Laichkraut Potamogeton pectinatus . According to the latter type, the vegetation unit is also called pectinati by some vegetation experts with the synonymous name Kammlaichkrautfur Potamogetonion (or Potamion). Companions are, for example, the submerged form of the crab claw Stratiotes aloides and the milfoil Myriophyllum spicatum . Often there is also the non-rooting rough horn leaf Ceratophyllum demersum, which drifts freely in the water . According to the EU manual, the species specular pondweed Potamogeton lucens , long-leaved pondweed Potamogeton praelongus , narrow-leaved pondweed Potamogeton × zizii are also characteristic of the habitat type . The society occurs in predominantly natural, eutrophic, mostly base-rich waters up to a water depth of about four meters. It is of great importance for the ecology of the waters, whose self-cleaning power it supports, and it is an important spawning area for fish species.
Small spawn dive corridors
The small spawn dive corridors are the characteristic vegetation unit of the diving leaf zone of nutrient-poor waters, and they also appear as initial societies in disturbed or newly created eutrophic waters. In the plant-sociological system they form the association Parvo-Potamogetonion (from Latin parvus: small). They are more typical for shallow bank zones and rarely occur below 80 centimeters of water depth. They are absent in the diving zone of typical lakes.
Distinguishing species in disturbed or initial waters are about Small pondweed Potamogeton pusillus , Potamogeton acutifolius Potamogeton acutifolius , potamogeton trichoides Potamogeton trichoides , Chara vulgaris Chara vulgaris , Eleocharis palustris Eleocharis palustris , often comes zannichellia palustris Zannichellia palustris ago. The grass pondweed Potamogeton gramineus is typical of lime-poor and mostly nutrient-poor waters . The alpine pondweed Potamogeton alpinus is characteristic in cold, nutrient-poor waters .
- Strasburger: Textbook of Botany , 29th edition, arr. by D. von Denfer et al., G. Fischer, Stuttgart 1967, p. 167 f (II. transformations of the corm: 1. Aquatic plants (hydrophytes))
- Heinz Ellenberg: Vegetation of Central Europe with the Alps , Ulmer, Stuttgart 1963, pp. 382–401 (CI1: Still water and its siltation)
- Fritz Runge: The Plant Societies of Central Europe , Aschendorff, Münster 1994 12./13. improved edition, p. 36 ff (freshwater societies, Potametea)
- Siegfried Slobodda: plant communities and their environment , Urania, Leipzig 1985, p 163
- Siegfried Slobodda: plant communities and their environment . Urania, Leipzig 1988 (2nd edition) pp. 166f
- Peter Englmaier (2014): The Macroflora of Freshwater. Denisia 33: 313-345.
- Heinz Ellenberg : Vegetation of Central Europe with the Alps in an ecological, dynamic and historical perspective. 5th, heavily changed and improved edition. Ulmer, Stuttgart 1996, ISBN 3-8001-2696-6 , p. 440.
- Natural eutrophic lakes with magnopotamion or hydrocharition type vegetation BfN Federal Agency for Nature Conservation: The habitat types and species (protected objects) of the Habitats and Birds Directive. Last change: December 16, 2011.
- I.4.1.3 Potamion pectinati at infoflora.ch, The national data and information center for the Swiss flora. Last updated February 8, 2018.
- European Commission (editor): Interpretation Manual of European Union Habitats. April 2013 PDF
- Christian Berg, Peter Bolbrinker, Knut Arendt: 5th grade: Potamogetonetea Klika in Klika & V. Novák 1941 - Limnian Laichkraut societies. In Christian Berg, Jürgen Dengler, Anja Abdank, Maike Isermann (editor): The plant communities of Mecklenburg-Western Pomerania and their endangerment. published by the State Office for the Environment, Nature Conservation and Geology Mecklenburg-Western Pomerania. Weissdorn Verlag, Jena 2004.