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Urwald relict species – Saproxylic beetles indicating structural qualities and habitat tradition
(2005)
On the basis of the list of saproxylic beetles of Germany, the authors present a definition and list of “Urwald relict species”, comprising 115 beetles that are considered to be associated with primeval forest (“Urwald”) structures and features. We use the term “habitat tradition” to describe a continuity in supply of old growth dead wood and forest structures. The selection of species is made on behalf of the following criteria: relict records in Central Europe; attachment to continuity of deadwood resources and habitat tradition; continuity of old growth stand features like tree and deadwood maturity and di-versity; absence from cultivated Central European forest.
The habitat requirements of most Aradidae and the decisive factors that influence their occurrence are still poorly understood. To reduce this lack of knowledge a standardised survey of Aradidae in two large beech forest areas of Bavaria (northern Steigerwald and High Spessart) was conducted. The following hypotheses were tested: 1) With increasing habitat tradition (temporal continuity), population densities of Aradidae increase, 2) Increasing dead wood supply supports higher abundance of Aradidae, 3) There are key structures for particular species with respect to type of dead wood, diameter and exposure to sunlight, and 4) The occurrence of particular fungi species determines the occurrence of Aradidae. In our study, Aradidae were sampled in point sample plots by flight-interception traps and time-standardised hand collection. To analyse specific habitat requirements additional sampling was performed to increase the sample size. Four species of Aradidae were observed in the two forest areas: Aneurus avenius, Aradus betulae, A. conspicuus and A. depressus. The results demonstrate that all species have different and specific habitat requirements. Especially for A. betulae habitat tradition of standing dead wood of large dimensions infested by Fomes fomentarius seems to be crucial. Hence, A. betulae was only observed in the Spessart and only at the sites with habitat tradition.