Not as arid as the tundra, the taiga is associated with the sub-Arctic regions of the Canadian Shield and is characterized by a greater number of both plant (600) and animal (206) species, many of which live there all year. The taiga covers about 20% of the total area of Quebec. The Canadian boreal forest is the northernmost and most abundant of the three forest areas in Quebec that straddle the Canadian Shield and the upper lowlands of the province. Given a warmer climate, the diversity of organisms is also higher, since there are about 850 plant species and 280 vertebrates species. The Canadian boreal forest covers 27% of the area of Quebec. The mixed forest is a transition zone between the Canadian boreal forest and deciduous forest. By virtue of its transient nature, this area contains a diversity of habitats resulting in large numbers of plant (1000) and vertebrates (350) species, despite relatively cool temperatures. The ecozone mixed forest covers 11.5% of the area of Quebec and is characteristic of the Laurentians, the Appalachians and the eastern lowlands forests. The third most northern forest area is characterized by deciduous forests. Because of its climate (average annual temperature of ), it is in this area that one finds the greatest diversity of species, including more than 1600 vascular plants and 440 vertebrates. Its relatively long growing season lasts almost 200 days and its fertile soils make it the centre of agricultural activity and therefore of urbanization of Quebec. Most of Quebec's population lives in this area of vegetation, almost entirely along the banks of the St. Lawrence. Deciduous forests cover approximately 6.6% of the area of Quebec.