Boxes mimicking tree hollows can help conservation of saproxylic beetles

Published source details Jansson N., Ranius T., Larsson A. & Milberg P. (2010) Boxes mimicking tree hollows can help conservation of saproxylic beetles. Biodiversity and Conservation, 10531-9.
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Summary

A study was undertaken in southern Sweden to evaluate to what extent wooden boxes designed to mimic tree hollows and filled with different combinations of substrates would be used by rare and endagered saproxylic organisms associated with large pedunculate oaks Quercus robur.

The study was conducted 15-20 km southeast of Linköping, Östergötland. Three study sites (Brokind, Bjärka Säby and Grebo) with many hollow oaks known to support a species-rich saproxylic invertebrate fauna were selected.

A total of 48 oak wood boxes (70 x 30 x 30 cm) were constructed to resemble conditions (temperature and moisture) in hollow oaks. The bottom inside each was covered with 5 cm clay (in a bowl shape) to help retain moisture. Boxes were 70% filled with substrate, the bulk comprising oak wood sawdust (60%), oak leaves (30%) and hay (10%), plus 1 litre lucerne flour and 5 litre water. One of the following was also added: potatoes; oat flakes + additional flour; chicken dung; or a dead hen Gallus domesticus.

Boxes were placed on the shadiest side of tree trunks at about 4 m height. To investigate the importance of distance from dispersal sources, boxes were placed at different distances (0 to 1,800 m) from the three species-rich sites. The boxes were left for four seasons, start year varied: Brokind 2002; Bjärka Säby 2003; Grebo 2004).

Over three years, 3,423 specimens of 105 saproxylic beetle species were caught in 47 boxes (one box lost over the study period). Of beetles found in hollow oaks that were either tree-hollow species, bird nest species, or wood rot species, 70% were also found in the boxes. The contents of the boxes, as well as the distance to areas with large oaks, had detectable but modest influences. A box with a dead hen added to the substrate had the highest number of beetles. The number of species associated with oak tree hollows decreased with distance from sites with hollow oaks. In conclusion, the prospects for using such boxes for boosting substrate availability, or to fill spatial and temporal gaps therein, for saproxylic beetles are good.

Note: If using or referring to this published study, please read and quote the original paper, this can be viewed at: http://dx.doi.org/10.1007/s10531-009-9687-2