Summer browsing by moose on Scots pine

Abstract

Moose (Alces alces L.) browse Scots pine (Pinus sylvestris L.) mainly during the winter. There is a growing concern also regarding summer browsing by moose on Scots pine. We studied summer browsing on Scots pine during two consecutive years. In a survey of 47 stands in 2003, current summer browsing was found for 20.4% of the Scots pine main stems, and on almost half of them (9.8%) the top shoot was browsed. This indicates that the pine damage causing reduced wood quality was as serious during summer as during the preceding winter. There was significantly more summer browsing on previously browsed pines, compared to a random use, both at tree and stand level, and summer browsing was also spatially clumped within stands. Browsing on top shoots occurred up to a height of 2.8 m, whereas side shoot browsing was recorded for pines with a height up to 4.8 m. In 2004, 11 of the 47 stands were randomly selected for a more detailed study of pines browsed during that summer. The summer browsed trees contained, on average, 114 current shoots tree⁻¹, and 10.5 shoots tree⁻¹ (9.2%) were browsed. In this area, summer browsing may explain a considerable part of the moose-related forest damage recorded. The proportion of pines subjected to summer browsing did not change with availability of pines. Hence, increasing the number of Scots pine trees in young stands may be a way to increase the number of unbrowsed pine trees at a given moose population density.

Keywords:

• Alces alces L.
• moose
• Pinus sylvestris L.
• Scots pine
• summer browsing
• top shoot

Acknowledgements

The study was financed by Holmen, The Swedish Association for Hunting and Wildlife Management, and The Forest Research Institute of Sweden. We also thank Linda Burström for performing the fieldwork in the 2004 study.