Where does the taiga end and the tundra begin?

The boundary between the taiga (or boreal forest) and the tundra is defined by the tree line, which marks the absolute northern limit of tree growth.12

Rather than a sharp, singular line, this transition is often a complex, gradual mosaic known as the forest-tundra zone. In this region, patches of trees—often stunted or sparse—intermingle with tundra vegetation. North of the closed-canopy forest, the landscape shifts into a lichen woodland, followed by the forest-tundra, before finally giving way to the open, treeless plains of the Arctic tundra.31

The position of this boundary is primarily controlled by summer warmth, specifically the length and intensity of the growing season. Scientists have historically correlated the tree line with the 50 °F (10 °C) July isotherm. Because this transition is influenced by local topography, moisture, and maritime effects, the boundary fluctuates across continents, extending further north in areas warmed by ocean currents and dipping southward in coastal regions exposed to cold polar air masses.31