Grow low – The most striking thing about hiking above treeline is the view afforded by the dwarfed vegetation, some reaching only a couple of inches tall. By growing this low to the ground many of these plants stay below the snowpack in the winter and avoid blowing ice. Instead of standing upright, black spruce and balsam fir grow horizontally and form krummholz (“crooked wood”) vegetation. Low growth also allows plants to avoid high winds and stay warm. Try lying down on a windy day above treeline to notice the difference. Diapensia forms in a tight mat of tiny leaves only an inch or two above the ground. It is one of the best examples of this type of adaptation and is able to survive in some of the most exposed areas above treeline, even where snow is blown off during the winter.
Evergreens get an early start – Many plants above treeline hold on to their leaves over winter. These plants can begin photosynthesis as soon as growing conditions permit and take full advantage of a short growing season. Evergreens also don’t need to reaquire the nutrients needed to develop a new set of leaves each growing season. Although we immediately think of conifers such as balsam fir and black spruce as evergreen, above treeline, other evergreen plants include mountain cranberry, moss plant, diapensia, crowberry, Labrador tea, Lapland rosebay, and many others.
Subsisting on insufficient soils – Most of the soils above treeline are acidic, thin, or non-existent, and offer limited nutrients to the plants growing there. Lichens are a group of organisms that are well adapted to this situation, and can be found covering nearly all rock surfaces in the alpine zone. Lichens are actually two or more organisms living in an association that allows them to survive in places where neither could survive alone. One of the organisms is an alga or bacterium, which is able to photosynthesize and turn sunlight into sugar. It provides some of this energy to its partner; a fungus. In turn, the fungus houses the alga/bacterium and protects it from drying out, and produces enzymes that allow it to collect nutrients directly from the substrate that it grows on. As they grow and decay, lichens often begin the process of soil accumulation for the plants that will follow. Members of the heath family are another well-adapted group of plants. They are one of the best-represented groups above treeline and include bilberries, blueberries, cranberries, alpine azalea, Lapland rosebay, and others. Member of the heath family are also common in nutrient poor bogs found at low elevations.
Don’t dry out – Despite tremendous amounts of rain and cloud moisture, alpine plants are subject to drought. Water is not retained in the thin soils and the persistent winds rapidly dry out leaves. The fuzzy underside of Labrador tea is believed to comb water droplets from clouds and act like a sponge to keep the leaf surface moist. Mountain cranberry and many other alpine plants demonstrate another adaptation and develop a waxy cuticle that covers leaf surfaces and seals in moisture.
Perennials persist – Plants that must complete their entire life cycle in a year (annuals) don’t do well in extreme environments; one bad year and a population is likely to disappear from that area. Perennials can store extra energy during a good year to make it through a bad year. With one exception, all alpine species in our region are perennials. In addition, since relying on seed set for reproduction is such a risky strategy, many plants above treeline reproduce vegetatively rather than sexually.