The subarctic region has few food plants. Most of them give a fairly low output, energywise. It's fish and game that are the major sources of food there. Here I show you three plants that has a fairly good output. If you have a woman or two ( ;-) ) gathering these plants for several hours of the day I think you could at least achieve almost the needed calorie intake, at least combined.
You can not eat too many of these berries, but they contain a fair amount of sugar and vitamin C. They also store quite well. The Saami hid these for the winter under overhanging waterfalls. I love the taste of these and snack or gather them whenever they are available. The actual colour is more yellow than on the photo.
Viking era candy. All the plant is edible. Very spicy and too much flavour to eat alone in my opinion. Very good boiled with meat or fish. It's not so abundant and can be difficult to find in quantity. Also contains vitamin C.
The whole plant is edible. The seeds taste a little nutty, but are hardly worthwhile collecting and processing (winnowing). Quickly fried in the coals, the roots which can be of quite decent size, taste almost like french fries.