Alpine plant - WikiHQ

Alpine plants are plants that grow in an alpine climate, which occurs at high elevation and above the tree line. There are many different plant species and taxa that grow as a plant community in these alpine tundra. These include perennial grasses, sedges, forbs, cushion plants, mosses, and lichens. Alpine plants are adapted to the harsh conditions of the alpine environment, which include low temperatures, dryness, ultraviolet radiation, wind, drought, poor nutritional soil, and a short growing season.

Some alpine plants serve as medicinal plants.

thumb|upright=1.2|Alpine meadows in the [[Kazbegi National Park, Georgia]]

Ecology

Alpine plants occur in a tundra: a type of natural region or biome that does not contain trees. Alpine tundra occurs in mountains worldwide. It transitions to subalpine forests below the tree line; stunted forests occurring at the forest-tundra ecotone are known as Krummholz. With increasing elevation, it ends at the snow line where snow and ice persist through summer, also known as the Nival Zone.

Alpine plants are not limited to higher elevations. However, high-elevation areas have different ecology than those growing at higher latitudes. One of the biggest distinctions is that the lower bound of a tropical alpine area is difficult to define due to a mixture of human disturbances, dry climates, and a naturally lacking tree line. The other major difference between tropical and arctic-alpine ecology is the temperature differences. The tropics have a summer/winter cycle every day, whereas the higher latitudes stay cold both day and night.

In the northern latitudes, the main factor to overcome is the cold. Frost action processes have a strong effect on the soil and vegetation of arctic-alpine regions. Tropical alpine regions are subject to these conditions as well, but they seldom happen. Because northern alpine areas cover a massive area it can be difficult to generalize the characteristics that define the ecology. One factor in alpine ecology is wind in an area. Wind pruning is a common sight within northern alpine regions. Along with wind pruning, wind erosion of vegetation mats is a common sight throughout Alaska.

Growth

thumb|Saxifraga

Long-lived perennial herbs are the most common type of plant in alpine environments, with most having a large, well-developed root and/or rhizome system. Arenaria bryophylla is the highest flowering plant in the world, occurring as high as .

To survive, alpine plants are adapted to the conditions at high elevations, including cold, dryness, high levels of ultraviolet radiation, and difficulty of reproduction. These conditions are linked to topographical slope, ultimately affecting plant diversity and distribution. This is due to steeper slopes causing faster soil erosion which in turn impedes plant growth, seed distribution, and seed settlement. Furthermore, the slope of the topography directly affects many other abiotic factors including temperature, solar radiation, moisture content, and nutritional content in the soil.

Surviving low temperature extremes

Alpine habitat on [[Mont Blanc Massif|thumb]]

Most alpine plants are faced with low-temperature extremes at some point in their lives. There are several ways that a plant can survive these extremes. Plants can avoid exposure to low temperature by using different forms of seasonal phenology, morphology, or by variable growth form preference. One way is to hide most of the plant in the soil and only letting the flowers and leaves be exposed to air. They can also avoid the freezing of their exposed tissues by increasing the number of solutes in their tissues, known as freezing-point depression. Another, somewhat similar, method plants may use to avoid freezing is supercooling, which prevents ice crystallization within plant tissues. These methods are only sufficient when the temperature is only moderately cold. In the alpine zone, temperatures are often low enough that these methods are not sufficient. When plants need a more permanent solution, they can develop freeze tolerance. Plants can also dehydrate their cells by moving water into intercellular spaces. This causes ice formation outside of the cell where ice crystals will not cause damage. When all of these strategies fail to prevent frost damage, alpine plants often have the capacity to repair or replace the organs damaged. As it is often difficult to prevent damage, many alpine plants depend on the replacement of their organs. They help make this possible by placing their meristems below ground, where temperatures are generally warmer. At the start of the growing season, new shoots have low net photosynthesis rates and high respiration rates due to rapid growth of new shoots. Among higher plants, tissue desiccation is rare at high elevation. If it does occur, it normally happens to plants growing on exposed sites, where wind stress is increased. Alpine plants avoid water loss by deep rooting and increased stomatal control. Plants at low elevation normally reach a maximum stomatal opening in the morning while alpine plants reach maximum opening mid-day when the temperature is greatest. Alpine succulent plants often utilize CAM photosynthesis to avoid water loss.

Avoidance of ultraviolet radiation

Because ultraviolet radiation tends to increase with elevation, it is often assumed to be a stress factor among alpine plants. In the past, there have been many attempts to research how ultraviolet radiation may influence alpine plant forms. However, it is uncertain if the growth and development of plants are affected by ultraviolet radiation. It is also not clear if the radiation is responsible for promoting genetic differentiation, leading to stunted growth forms. The most common pollinators in the alpine zone are bumblebees and flies. Because of early-season pollinator limitation, plants that bloom early generally have a low rate of reproductive success.

Mid-season flowering

Approximately half of all alpine species flower in mid-season. Flowering at the seasonal peak combines some of the advantages and risks of early flowering and late flowering plants. Some mid-season plants pre-form their inflorescences, but not all do.

thumb|Erythronium grandiflorum

After establishment, each year new shoot growth occurs rapidly from the perennating bud which is usually located close to the soil surface. This creates an increased need to focus on plant conservation in these areas, ensuring sustainable harvest as well as ecosystem sustainability. Some of the species harvested in Nepal include Neopicrorhiza scrophulariiflora, Nardostachys grandiflora, Aconitum spicatum, Dioscorea deltoidea, Aconitum heterophyllum, Rheum australe, and Bergenia.

Notes

References

External links

Greek Mountain Flora
The genus Dionysia in Iran and Oman
The Alpine Garden, Rock Gardening on the Net
Japanese Alpine Plants, etc.
The Gardeners Resource
The Alpine Garden Society