Beetle diversity in high-stumps from Norway spruce thinnings

Dead wood is regularly created during cutting operations in Fennoscandia. It has been shown that high-stumps (snags) created at final felling can be important for many saproxylic beetles, including red-listed species. However, the importance of thinning high-stumps has yet not been studied. In this study, one- and three-summer-old Norway spruce high-stumps from first thinnings, third thinnings and final fellings were sampled by bark sieving in southern Sweden. None of the 73 species found was on the red list. The thinning high-stumps did not have lower species number or species density compared with the final felling high-stumps. Tree diameter was not positively correlated with the number of species. An ordination showed that the thinning high-stumps had a different composition compared with the final felling high-stumps. Of 16 species tested for preferences, 11 showed positive or negative association for one or two of the high-stump categories. The beetle Placusa complanata was caught in thinning high-stumps only. However, most of the species found in thinning high-stumps in this study are probably also common in final felling high-stumps in southern Sweden. Nevertheless, a general piece of advice based on this and other studies is that as many categories of dead wood as possible are preferable from a biodiversity point of view.