Tree retention practices in boreal forests: what kind of future landscapes are we creating?

Tree retention practices promoting biodiversity may reshape future boreal forest production landscapes. Using the Heureka system, scenarios of 0%, 5%, and 20% retained patches at the stand level were projected over 200 years in a 533 ha boreal landscape. Visualizations of future forest states at a landscape scale and a more detailed scale were made based on the projections. The no retention results in no forest >120 years old, and no large trees (diameter at breast height >40 cm for conifers and >35 cm for broadleaved trees) 100 years from now. With retention levels of 5% and 20%, the area of old forest will comprise 7% and 19% of the total area, respectively. The average number of large trees per ha will be 4 and 13, respectively. Deadwood volumes will be 2.5 times higher at 5% retention and 4 times higher at 20% retention compared to no retention. Landscape visualizations indicate that retention patches covering 5% will marginally modify the visual impression, compared to clear-cuts, while 20% cover will create a much more varied landscape. We conclude that the retention approach is essential for restoring natural conditions. Landscape transformation will be slow and depend on starting conditions and retention levels.