Junsele moose do not avoid forests with the non-native contorta pine

In Sweden, pine forests are the most important habitat for moose, especially during winter when pine is their primary food source. More than 50 years ago, native Swedish Scots pine was joined by the fast-growing North American Lodgepole pine (Pinus contorta), introduced into forestry in northern Sweden, shortly named contorta pine. The species has been controversial because introducing a non-native tree species may have consequences for biodiversity.

The Junsele area contains a large proportion of young forests with contorta pine compared to other parts in Sweden, and for the first time researchers have been able to study how moose move through such a forest landscape. Over a two-year period, they followed 29 GPS-collared moose to investigate whether the non-native tree species influenced individuals’ habitat selection.

– Our results show that moose use young forests dominated by contorta pine to the same extent as young forests with native Scots pine. We found no indication that they avoid areas with contorta pine. Instead, they selected this habitat year-round, says Wiebke Neumann, researcher at SLU.

Different factors influence habitat selection

The reasons behind this are not yet fully understood, but several factors influence moose habitat selection, including food availability and season. Previous research has been inconclusive regarding the extent to which moose browse contorta pine. Twigs from native Scots pine and deciduous browse are important food sources in both summer and winter. During winter, other factors such as shelter from weather and wind are also important.

The study also showed that moose selected older contorta pine forests with trees up to 15 meters tall to a similar extent as comparable forests dominated by native Scots pine.

– Contorta pine has a denser crown and a bushier growth form. The canopy may intercept large amounts of snow, which could make it easier for moose to move beneath the trees. Even during summer we observed that moose selected contorta pine forests where the trees were up to 15 meters tall. Perhaps temperatures are lower there, providing shade and cooling during warm days, but we have not studied that in detail, says Wiebke Neumann.

Reindeer avoid contorta pine stands

The dense branches of contorta pine reduce the amount of light reaching the ground, which leads to lower growth of bilberry shrubs and lichens. A previous study conducted by researchers at Umeå University and SLU showed that reindeer avoided dense, tall contorta pine stands during winter grazing because they could not find ground lichens there. Instead, they preferred areas dominated by native Scots pine.

According to the researchers, more studies on contorta pine in Sweden are needed.

– Contorta pine is often planted under the assumption that it will be browsed less by moose than native Scots pine. We need to study how moose actually use contorta pine stands and how the proportion of contorta pine affects animals’ browsing pressure across different parts of the forest landscape, says Wiebke Neumann.

Scientific article

Habitat selection of moose in Sweden in managed boreal forests with Pinus contorta and P. sylvestris
Maria Bolund, Fredrik Stenbacka, Fredrik Widemo, John P. Ball, Göran Ericsson, Wiebke Neumann.
http://doi.org/10.1002/wlb3.01662