Long-term forest utilization can decrease forest floor microhabitat diversity: evidence from boreal Fennoscandia

Forest floor microhabitat diversity was studied in old Pinus sylvestris L. dominated forest sites in two regions within the middle boreal vegetation zone in Fennoscandia: in 50 managed forest sites in the H?me region in southwestern Finland and in 45 natural or old selectively logged forest sites in the Kuhmo–Viena region in northeastern Finland and northwestern Russia. The forests in the H?me region are characterized by a long history of forest utilization, while the forests in the Kuhmo–Viena region can be regarded as natural or near natural. The managed forest sites in H?me had significantly lower forest floor microhabitat diversity compared with natural and near-natural forests. Microhabitats that were significantly more scarce in managed versus natural and near-natural forest sites included humps, depressions, decayed wood, and vicinity of decayed wood. On the other hand, even ground was significantly more abundant in managed forest compared with natural and near-natural forest. Microhabitat availability was also reflected in the occurrence of tree saplings growing in different microhabitats. The results suggest that long-term forest utilization has decreased forest floor microhabitat diversity. This has occurred because of a decreased amount of fallen deadwood and, possibly, lack of soil disturbances because of fewer uprootings caused by falling trees.