Saproxylic beetles as indicator species for dead-wood amount and temperature in European beech forests

Abstract

Beech forests in Central Europe are under strong anthropogenic pressure. Yet they play a fundamental role for biodiversity and are therefore increasingly considered in conservation activities. Sites of high conservation value can be efficiently defined by the use of indicator species, but very few studies have identified indicator species for beech forests on a continental scale. Here we determined the efficacy of saproxylic beetles as indicator species for European beech forests and studied the effect of the amount of dead wood and temperature on their presence. We analyzed data from 988 trap catches from 209 sites in 7 European countries. Using the flexible indicator approach, which allowed combinations of two temperature groups (warm and cool) and three dead-wood amount categories (small, intermediate, high) to be considered, we identified 127 indicator species. Generally, we found more indicator species of beetles at warmer sites and at sites with larger amounts of dead wood. Indicator species at cooler sites were found only in combination with larger amounts of dead wood. We present a comprehensive, data-based list of indicator species of saproxylic beetle for near-natural beech forests, as required in the framework of the European Natura-2000 concept for habitat evaluation. We identified the conspicuous Lucanidae as the family with the highest percentage of indicator species and thus recommend it as a priority indicator group for monitoring. Our results furthermore provide evidence that large amounts of dead wood are particularly important in cool, montane beech forests for maintaining high diversity.