Ecological Zones: A Hike Up Mount Washington Ascending 1000 vertical feet in the mountains of the northeast can be likened to driving hundreds of miles north. On average temperatures decreases 3 to 5oF and precipitation increases by 8 inches a year with each 1000 foot elevation gain. As a result, the plant and animal communities change drastically as you hike up a mountain. I. The Northern Hardwood Forest and Transition Zones (less than 2500 ft) Primarily deciduous forest, dominated by sugar maple, American beech, and yellow birch. Other trees include red maple, red oak, black cherry, paper birch, hemlock, and white pine. A variety of shrubs, ferns, and wildflowers are also found in this zone. At or above 2000 ft the northern hardwood forest gives way to a transition zone in which spruce and fir trees intermix with sugar maple and other deciduous trees. As elevation increases, hemlocks and pines and most deciduous trees are unable to grow. Of the primary hardwood forest trees, yellow birch is able to grow at the highest elevation. II. The Spruce-Fir Forest Zone (2700-4000 ft) Temperatures are colder, leading to a shorter growing season. The combination of cold temperatures and higher precipitation leads to wetter, more acidic, and less fertile soils because decomposition of organic matter is slower at lower temperatures and large amounts of precipitation leeches nutrients. In these conditions, evergreen conifers, especially red spruce and balsam fir, have an advantage over most deciduous trees, although paper birch, striped maple, and mountain maple are still found in the lower elevations of this zone. III. The Balsam-Fir Forest Zone Around 4000 feet red spruce drops out and as you continue climbing the forest is almost entirely balsam firs. As elevation increases, the balsam fir forests become stunted. As forests approach the upper elevation limit for their upright growth, they form a nearly impenetrable thicket or “tuckamore”. Krummholz, “Crooked Wood” Zone (up to 5400 ft) The Krummholz or “crooked wood” zone consists of dwafted trees, primarily balsam fir and black spruce. This zone is not contiguous, rather Krummholz is found in the dwarfed balsam forest ringing the alpine zone and in small patches within the alpine zone itself. Trees are dwarfed due to harsh growing conditions and extreme wind and ice abrasion leads to the gnarled shapes. In the Krummholz, balsam fir and black spruce form prostrate mats, hugging the ground to escape the wind. When trees grow upright, the windward branches often die, leaving green branches on only one side of the tree: a “flag tree”, signaling the prevailing wind direction. Prostrate balsam fir Flagged krummholz trees What determines treeline? Interestingly, it is not the winter cold, but the lack of summertime heat that correlates best with treeline. The length of the growing season determines whether a tree has enough time to produce and harden new growth before the first frost The limit of tree growth in both the alpine zone and the arctic is close to the 54oF isotherm for the warmest month of the year. IV. Alpine Zone Life is harsh in the alpine zone, with a short growing season, extremely cold temperature, and strong winds. To survive in the alpine environment, plants capitalize on a number of adaptations, including small size, compact shapes to conserve heat, creeping mats to anchor the plant to the ground, protective hair, and narrow leaves that bend in the wind. Despite the harsh environment a large number of species are found in the alpine zone. Wind pollinated sedges, grasses, and rushes are a major component of alpine flora. Spore bearing plants, such as ferns and clubmosses, have well-developed food and water conducting systems and thus are well adapted to alpine environments. Mosses, liverworts, and lichens adorn even available surface, from windblown ground, to rocks, to branches and even small trigs. A variety of dwarfed shrubs are also found in alpine regions, including Lapland rosebay, several species of blueberries, mountain cranberry, and Labrador tea. Finally, a good number of perennial herbaceous plants are able to survive in alpine areas; dazzling displays of flowers mark the coming of spring in alpine areas. Harebell and other flowers in Alpine Garden on Mt. Washington in spring Alpine Communities Due to the extreme habitats in the alpine zone, many plants exist only in very specific niches. Therefore, alpine flora and fauna are often divided into “communities”. The most common communities on Mt. Washington include: Bigelow Sedge Meadow Communities Most common community on the upper slopes of Mt. Washington: The Sedge community looks like a grassy field but it is actually a Bigelow Sedge meadow, kept moist by fog and frequent rain. Little else grows except mountain sandwort. Dwarf shrub/heath/rush communities Species rich community found on peaks within a few hundred feet of treeline: Covers much of the alpine garden on Mt. Washington. Sedges, highland rushes, dwarf shrubs are the prominent vegetation, but 17 species of vascular plants are also found as are a variety of mosses and lichens. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Dwarf Shrub/Heath Communities Primarily dwarf shrubs, such as bilberry, mountain cranberry, Labrador tea, bunchberry, and low-sweet blueberry are dominant. A number of rare flowering plants are also found in this community. The dwarf shrub/heath communities form dense mats with brown Icelandic lichen covering the ground underneath the shrubs. Diapensia Communities Inhabit the windiest, most exposed sites. Hummock shaped diapensia surrounded by patches of bare ground. Dwaft shrubs alpine azalea, Lapland rosebay, and bog bilberry as well as highland rush are found in this community. QuickTime™ and a TIFF (Uncompressed) decompressor are needed to see this picture. Info from: Slack, Nancy and A.W. Bell. AMC Field Guide to Alpine Summits, 2006.