The size of the field and the ditching on it as well as the condition of the field at the time of the surrender of Porkkala area (from Finland to Russia) play an important role on how far the natural regeneration of the fields has progressed.
Larger open fields have naturally regenerated only on sides where the surrounding forest can spread the seeds or the thicket of saplings has reached, whereas small parcels of fields have normally been fully forested. Most important species have been e.g. silver birch and pubescent birch, grey and common alders and European aspen as well as pine and spruce. The broad leaved species are dominant.
The PDF contains a summary in Finnish.
The vegetation in the Pacific coasts of British Columbia and Southeastern Alaska resemble the vegetation in the northern Fennoscandia. The national forests have been divided in two parts: Tongass and Chugach national forests. Both of the forests are fairly uniform in their vegetation. The forests have few coniferous tree species as the dominant species from south to north, Sitka spruce (Picea sitchensis (Bong.) Carrière) and western hemloch (Tsuga heterophylla (Raf.) Sarg.). It is difficult to distinguish forest site types, but it is probable that the forest lands in Alaska and British Columbia could be delimited to similar forest site types as professor Cajander established in Finland.
The volume 34 of Acta Forestalia Fennica is a jubileum publication of professor Aimo Kaarlo Cajander.