Back home, the catalyst for the worst biotic catastrophe in the world, the Siberian Traps, don't have much left. 252 million years of erosion was more than enough to reduce the igneous province from an area of 770,000 square miles and a volume of 240,000 to 960,000 cubic miles to a pale shadow of its former self.
Here are the Siberian Traps from an alternate Earth, which erupted from 60 to 43 million years ago instead of 252, covering an area of 11 million square miles and a volume of four million cubic miles.
43 million years of erosion obviously result in an altogether different erosion than the 252 of OTL, but to what extent? Using the specified details above, would we still see vast, singular bands of boreal forests and steppes, or would we expect to see Russia hosting a wider variety of habitats?