Douglas fir and Norway spruce have similar effects on small mammal density, but not survival, in Central European managed forests

Abstract

In an effort to ameliorate the impacts of climate change, forest managers in Central Europe increasingly turn to conifer species that produce higher yields and are better adapted to projected future climatic conditions. Though small mammals are an important component of the forest ecosystem, the impacts of enriching native broadleaf forests with conifers on small mammal communities are not well understood. We conducted mark–recapture surveys of small mammals to ascertain differences in their community structure among stands of two conifers (native Norway spruce Picea abies and non-native Douglas fir Pseudotsuga menziesii) and the dominant broadleaf in the region, European beech (Fagus sylvatica). After estimating the density of two common species, the yellow-necked mouse Apodemus flavicollis and bank vole Clethrionomys glareolus, we found that the population density of each is positively related to the proportion of beech and negatively to the proportion of conifers in each stand, though these effects of stand composition are smaller than the positive effect of herb cover. Increasing Norway spruce proportion reduced monthly survival of small mammals, while Douglas fir proportion had a positive effect on survival. We conclude that the two conifer species have similar impacts on small mammal density, though overall small mammal survival was significantly lower on plots with Norway spruce. This suggests that increasing the proportion of Douglas fir at the expense of Norway spruce may be possible without significantly changing local patterns of small mammal population density, but further research is necessary to elucidate the exact impacts of these two conifer species on small mammal demography and behavior.