Today many saproxylic species are threatened because of habitat decline in Europe. Hollow trees represent a great part of the habitats that saproxylic species use. Since hollows takes a long time to develop, management actions are needed to prevent the extinction of saproxylic species. The aim of this study was to investigate the succession of saproxylic beetle species in artificial habitats in the form of wooden boxes. Wooden boxes were filled with a potential substrate and placed at different distances (0-1800 m) from oak hollow hot spots. In addition to the start mixture, four different additional substrates were added. In total, 4510 specimens of 114 saproxylic beetle species were sampled in 43 boxes over ten years. The specimens of tree-hollow species, wood rot species and nest species increased with 38% from the fourth to the final year but species richness decline from 47 to 29, respectively. A dead hen had a tendency for attracting more species but the small effect of different added substrates diminished over the years and had no significant effect on species richness after ten years. There was a higher similarity in species richness after ten years between the boxes and real hollow oaks. In conclusion, the artificial habitat developed into a more hollow like environment, with fewer but more abundant wood mould specialists, during ten years. This study clearly shows that the wooden boxes are used as habitats for saproxylic species as the boxes seems to develop into a more hollow-like habitat with time.

Old hollow trees of oak contain a large amount of wood mould. Unfortunately, these trees have in the last century been greatly reduced in numbers. It has resulted in that species that depend on these habitats, saproxylic species, have become at risk to decrease in numbers or die out regionally. Previous studies have shown that the volume of wood mould is an important factor for occurrence and population size of saproxylic organisms. The aim of the present study was to examine how the volume of wood mould varies among ash (Fraxinus excelsior), lime (Tilia sp.), maple (Acer platanoides), aspen (Populus tremula) and oak (Quercus robur). The measurements were wood mould depth, internal cavity diameter, internal cavity height, circumference, and if white or brown rot was the dominating mould fungus. In total 23 ashes, 20 limes, 24 maples, 24 aspens and 21 oaks in the vicinity of Motala (Östergötland) were measured. The results show that there were significant differences between tree species concerning the volumes of wood mould. The oak accommodated larger volumes than the other species. The ash, however, had a larger volume than oak at the same circumference. The study shows ash could be a complement to the oak in conservation plans. Since the ash generally holds a larger volume then the oak at the same circumference, this implies the possibility that the ash can be suitable for saproxylic organisms at an earlier stage. In the isolated fragments of the landscape the possibility for survival may then increase for species that are dependent of these habitats. / Gamla hålträd av ek hyser ofta en stor mängd mulm. Tyvärr har dessa träd det senaste århundradet minskat i antal. Det har fått till följd att arter som är beroende av dessa habitat riskerar att minska eller dö ut regionalt. Tidigare studier har visat att volymen av mulm i ett träd är en viktig faktor för förekomst och populationsstorlek. Syftet med denna studie var att undersöka hur mulmvolymer varierar mellan olika trädslag. Mulmvolymen mättes därför hos ask ( Fraxinus excelsior), lind (Tilia sp.), lönn (Acer platanoides), asp (Populus tremula) och ek (Quercus robur). På varje träd mättes mulmdjup, invändig håldiameter, invändig hålhöjd, omkrets samt om trädet hade vitröta eller brunröta. Sammanlagt mättes 23 askar, 20 lindar, 24 lönnar, 24 aspar och 21 ekar runt Motala (Östergötland) med omnejd. Resultaten visar att det finns signifikanta skillnader mellan trädslagen gällande mulmvolymer. Eken hyser större volymer än de övriga, men ask och lönn har även de relativt stora volymer mulm. Asken har dock större volym mulm än vad eken har vid samma omkrets. Studien visar att man vid naturvårdsplaneringar bör ta med ask som ett komplement till eken i ett fragmenterat landskap. Eftersom asken kan generera större volymer mulm än eken vid samma omkrets medför detta möjligheten att asken kan fungera som habitat i ett tidigare skede. I isolerade fragment av landskapet kan då chansen för överlevnad möjligtvis öka för de arter som är beroende av mulmhabitat.