Saproxylic beetles in high stumps of spruce: Fungal flora important for determining the species composition

In most Swedish felling operations high stumps are created from living trees to increase the amounts of dead wood in the forest. The fauna of saproxylic beetles and aradid bugs (Heteroptera) in spruce (Picea abies) high stumps were studied to determine which characteristics (diameter, height, amount of bark and fungal flora) had the strongest influence on the species composition. The practical aim was to see whether it is possible to increase the biodiversity values by management recommendations. The high stumps (n = 59) were situated in the middle boreal zone in Sweden and were 6 years old. The insects were sampled by sieving 0.25 m(2) bark on each stump. In total, 803 saproxylic beetles and Aradus bugs were found, representing 42 different species, five of which were red-listed. The most important factor for determining the beetle community was the presence or absence of two polyporous fungi, Fomitopsis pinicola and Trichaptum abietinum. Other factors were much less important, indicating that it is difficult to influence the stumps' biodiversity values significantly simply by selecting trees of certain diameters or optimizing cutting heights.