Current issue: 58(4)
The moose (Alces alces L.), a common large herbivore in the boreal region, impairs forest regeneration by browsing on tree seedlings and saplings. Moose prefer deciduous species, but during winter more coniferous seedlings are used. We used meta-analyses, separately for deciduous and coniferous seedlings, for evaluating whether excluding moose browsing affected seedling density and height. In addition, we compared (1) deciduous seedling proportion, (2) stand density, (3) elapsed time from fencing and (4) estimated moose density with moose exclusion effect sizes. Fencing had a positive effect on coniferous seedling height. With more deciduous trees in a seedling stand, the fencing effect for both seedling height and density of coniferous seedlings decreased. On the other hand, the fencing effects increased with denser stands. At some point effect sizes turned to negative, and conifer species varied in their response to browsing. This implies that deciduous seedlings can protect conifers from browsing by moose up to some mixing ratio, but when deciduous seedling densities are too high, their negative effect increases, presumably through increased competition. Our results suggest that a moderate deciduous admixture in conifer-dominated mixed seedling stands can decrease moose damage but also underline the significance of timely silvicultural measures to minimize the negative effects of excessive deciduous seedlings and too dense stands. Due to differences in coniferous and deciduous species, as well as their compositions and amounts in studied experiments, more studies adjusted to local conditions are still needed to give exact measures for silvicultural recommendations.
Ungulate browsing results in important damages on the forests, affecting their structure, composition and development. In the present paper, we examine the occurrence of browsing damage in Norwegian forests, using data provided by the National Forest Inventory along several consecutive measurements (entailing the period 1995–2014). A portfolio of variables describing the stand, site and silvicultural treatments are analyzed using classification trees to retrieve combinations related to browsing damage. Our results indicate that the most vulnerable forest stands are young with densities below 1400 trees ha–1 and dominated by birch, pine or mixed species. In addition, stand diversity and previous treatments (e.g. thinnings) increase the damage occurrence and other variables, like stand size, could play a role on forest susceptibility to browsing occurrence although the latter is based on weaker evidence. The methods and results of our study can be applied to implement management measures aiming at reducing the browsing damages of forests.