Coniferous forest description
The coniferous forest is the largest of the state's three biomes. It covers two-fifths of the state, including the north central and northeastern regions. Once mountainous, this rugged area claims both the highest and lowest points in the state.
Glaciers sculpted this landscape, leaving relatively thin deposits of till blanketing the bedrock in the northeast and deeper deposits in the southern and western portions. Boulders, outcrops, hills, numerous lakes, bogs, and vast tracts of forest land comprise Minnesota's scenic and much beloved "up north." The state's iron ranges also occur here, along with many other Precambrian rocks and well-exposed lava flows. Dense forests occupy the uplands, with bedrock lakes in the northeast, ice block lakes in the south and west, and large, open peatlands in lower areas.
Cold winters and cool summers caused by Arctic air masses result in extreme temperature variations and a low energy budget for the plant communities found here. Most of the precipitation occurs during warm months, and the air and soils are moist in comparison to the non-forested landscapes of western Minnesota. Soils that have developed from glacial till and loess now thinly overlay the Canadian shield.
Species that succeed in this environment have adaptations that economize on energy--both temperature and sunlight--and on nutrient requirements. For example, coniferous trees hold their needles from 2 to 15 years, depending on the species. This adaptation avoids the necessity for producing a full crop of new leaves every spring, and it also allows photosynthesis for extended periods of the year. Species that occur in the boreal hardwoods, such as trembling aspen, balsam poplar and paper birch, have special adaptations to withstand temperatures below -30° Fahrenheit.
The canopy layer of a forest community may be seen as being the primary buffer between atmospheric conditions and the communities below; it bears the brunt of wind and temperature extremes, and is the first beneficiary of sunlight.
Coniferous Forest canopies may be dominated by coniferous, deciduous, or mixed coniferous-hardwood species.
Six forest communities are characteristic of Minnesota's Coniferous Forest area: white pine, red pine, jack pine, black spruce-feathermoss, spruce-fir, and upland white cedar. While all pines regenerate after fire, the fire regime differs for each species.
After a disturbance in the coniferous forest, such as logging or burning, the canopy opening favors deciduous species, with their higher rates of photosynthesis. Aspen and paper birch pioneer such areas, and they may in turn be followed by mixed hardwood and coniferous trees in a zone of intergrading communities. Northern hardwood stands of sugar maple, basswood, yellow birch, and associated species develop on mesic uplands. On drier sites in the south and west portions of the Coniferous Forest, oak communities are more common.
Beneath the canopy layer, shrubs vary locally in density. Seedlings and saplings of canopy trees bide their time in the shade; when a canopy tree falls, these young trees inherit the sunlight they need to succeed to canopy status themselves. Shrub-level species include beaked hazel, mountain maple, honeysuckle, and dogwood, along with others associated with specific soils and canopies. Variation of shrub density within the forest significantly affects the habitat and diversity of animal species.
The ground layer in coniferous plant communities often includes feathermosses as well as forest herbs. The acid needle litter on the forest floor supports herbs such as clintonia and rose twisted-stalk, while feathermoss communities support such herbs as wintergreen and pyrola.
The Coniferous Forest biome ranges from relatively flat lake plains and outwash plains in the west, to hillier moraines in the mid-section, with rugged, rocky outcrops abutting Lake Superior. Peatlands occur in huge areas across the western and central glacial lake plains. As elevation rises eastward, soils become thinner and bedrock outcrops more prominent. Here passing glaciers caught on rugged bedrock; ice blocks broke off and were abandoned to melt slowly beneath glacial till, forming many of our "10,000 lakes."