Central Canadian Shield forests
This ecoregion consists of rolling hills, lakes, bogs and rocky outcrops covering a large curved swathe on the Canadian Shield from eastern Manitoba and Northern Ontario running southeastwards through Thunder Bay District to the north shore of Lake Superior and then northeastwards into western Quebec. The area has a cool climate with summer temperatures averaging around 13°C dropping to a very cold -17°C in winter, with the hills around Lac Seul in northwestern Ontario being warmer and wetter than most of the area. Average rainfall in the eastern side of the ecoregion is 550mm per year, rising to 750mm in the centre (near Lake Nipigon for example), up to 900mm in the west. Specific areas include Lake Nipigon and Big Trout Lake (Ontario). These forest contrast with more severe boreal forest ecoregions such as the Eastern Canadian Shield taiga to the north, which covers most of Northern Quebec and Labrador.
Boreal forest of Canada
The particular mixture of tree species depends upon factors including soil moisture, soil depth, and organic content. Upland forests can be closely mixed with forested peatlands. The resulting conifer forests are produced by and dependent upon recurring disturbance from storms, fires, floods and insect outbreaks. Owing to the accumulated peat in the soil, and the predominance of coniferous trees, lightning-caused fire has always been a natural part of this forest. It is one of many ecosystems that depend upon such recurring natural disturbance. For example, fire dependent species like lodgepole and jack pine have resin sealed cones. In a fire, the resin melts and the cones to open, allowing seeds to scatter so that a new pine forest begins (see also fire ecology). It has been estimated that prior to European settlement, this renewal process occurred on average every 75 to 100 years, creating even-aged stands of forest. Fire continues to cause natural forest disturbance, but fire suppression and clear-cutting has interrupted these natural cycles, leading to significant changes in species composition.