| Summary: | Temperature decreases with latitude from the equator to the poles and with elevation from the lowlands to mountains peaks. A parallel change in biota, most apparent in how plant growth forms give rise to a sequence of tree-dominated biomes/vegetation belts, from tropical lowland evergreen rain forest to boreal taiga or upper montane forest, until tree growth form is no longer sustainable (latitudinal and elevational treelines) and the landscape changes into open low-stature shrub and forb vegetation: polar tundra at high latitudes and alpine vegetation in the mountains. While the concept of tundra biome is well established, no such thing as an “alpine biome” is recognized by most biogeographers. Biogeographically, the alpine “biome” is rather heterogeneous as it encompasses the climatically treeless cold-limited portions of mountain environments in all latitude climate/life zones from the tropics to the poles. The total extent of the alpine biome is estimated at being c. 3 percent of the total land surface of the Earth, where about 4 percent of known vascular plant species occur. The regional biological richness of alpine ecosystems is highly variable across continents, ranging from c. 200 plant species in the east African high volcanic mountains to more than 3,000 species in the north Andean “páramos.” Our knowledge of alpine ecosystems is uneven when mountains are considered worldwide. The Alps and other European mountains are well described botanically and zoologically, allowing comparative biogeographical analyses. Ecological and ecophysiological research in alpine ecosystems has been focusing on diversity/productivity-environment (primarily [micro-]climate) relationships: species acclimation, tolerance, and evolution, the bases of dispersal and distribution. The alpine biome has recently become a test field of the stress-gradient hypothesis and the focus of climate change impact studies, largely through modeling. The history and phylogeography of alpine organisms is also an active field. The number of population and community level studies is small in alpine ecosystems, and they are mostly associated with studying disturbance factors, such as (over)grazing or atmospheric deposition. While ecosystem services that alpine environments contribute to human well-being are increasingly being recognized, their sustainable use largely remains a theoretical consideration. Following major changes in land use in the 1960s, a large proportion of the biome is protected in economically developed countries; in developing countries it continues to provide important goods and services for sustaining local livelihoods. Initiatives are ongoing to undertake long-term integrated research to observe and report changes to the structure and functioning of alpine ecosystems in response to climate change and human land use.
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