Mammoth steppe


Hello there,
I had a shower thought yesterday about a possible terrain type for the area west of the Frostfangs beyond the wall. Implementing a Mammoth steppe might make sense there.
But what is the mammoth steppe?
It is a nowadays almost extinct biome which dominated Eurasia during the pleistocene and in the ice ages. It was a large steppe, pretty similar to the African savannah, just a "little" bit colder. The grasslands were sustained by the pleistocene Megafauna like big elks, wooly rhinocerus or Mammoths. They would trample the snow to a thin layer and destroy most mosses and other plants that nowadays exist in the tundra, while grasses could flourish. It also helped to keep the permafrost alive in the soil. With the lack of Megafauna since the end of the ice age, the Mammoth steppe died out. Two russian scientist are trying to recreate a Mammoth steppe in Northern siberia in the pleistocene park project. They are using the remains of the Megafauna like elks, bisons and horses as well as some old russian tanks to simulate the Mammoths, and they are succeeding in changing the local fauna and flora. But why did I get the idea that this could be used in Westeros?
In contrast to real Earth, Westeros has megafauna. Mammoths are still roaming around North of the wall, the giant antlers in our resource pack look like the giant Irish elk, and Giants could also work as Megafauna. Furthermore, Northern Siberia sounds like the land beyond the wall.
There are some small remain areas of the mammoth steppe, where high altitude has prevented trees from growing, as seen in the picture:

Here are pictures from the pleistocene park:
I know that we have to cover it with snow, but it could be a solution to the cluelessnes of the actual terrain in the ice river clans. It wouldn't need a forrest and maybe could sustain a few hunter and gatherers (human or giant).
I would appreciate some feedback whether the idea is garbage or actually useful