Effects of location of Norway spruce (Picea abies) stumps on their colonisation by insects in the mountains

Tree stumps provide habitat for insect assemblages, which are influenced by various factors. Among these factors, physical and chemical changes of the stumps, fungi developing in the dead wood and stump size are most often reported. However there is limited information about the abundance of insects in stumps that are located on mountains where there are different microclimatic conditions. The studies pointed at the determination whether the location of Picea abies stumps in mountains at different altitudes above sea level and on mountainsides with different sun exposure has an impact on the frequency of insects colonising them. The study was carried out in the Eastern Sudety Mountains situated in south-western Poland. The stumps were in clearcuts located at the altitudes 600–700 m and 900–1000 m above sea level and on southern and northern mountainsides. The insects were collected from 0.05 m² of bark from each stump and identified to the family, order or species level. The numbers of insects in the stumps were modelled with the use of the Poisson distribution or the negative binomial distribution and the generalised linear models. Picea abies stumps were colonised by insects from 16 families in 3 orders (Coleoptera, Diptera, Hymenoptera) in which the Coleoptera was most frequently represented by the families Cerambycidae, Curculionidae (with the sub-family Scolytinae). In the stumps located at the elevation of 900–1000 m there were 28% more insects than in the stumps at 600–700 m. The stumps located on mountainsides with northern exposure were colonised more abundantly by Cerambycidae. Numbers of Curculionidae in the stumps were affected by altitude. Most Curculionidae were found in the stumps located at the elevation 900–1000 m above sea level. The interaction of altitude and mountainside exposure showed more insects in the stumps at higher altitude, regardless of the mountainside exposure. The results showed that the total number of insects in the stumps was influenced by their location in mountains.