In 1889, American naturalist C. Hart Merriam refined Humboldt's insight over a summer of field research in the varied landscape of the southern ColoradoPlateau north of Flagstaff, ARIZONA. There, discontinuities in the composition of plant species occur abruptly and correlate well with changes in altitude.
Even so, climate gradients, especially temperature, remain important variables in the geographical distribution of vegetation zones, particularly as biogeographers uncover and monitor effects of global warming. The zone concept has also been useful in monitoring environmental degradation caused by human development and agricultural practices.
Most of the total biomass in this vegetative zone is found in the Northern Hemisphere, north of the boreal forest. Dominated by diverse species of summer green, broad-leaved deciduous trees, this zone occurs in temperate regions wherever precipitation and soils are suitable.
In warmer temperate regions, including southeastern United STATES, CHINA, and JAPAN, the place of these summer-green trees is taken by evergreen deciduous species. A vegetative zone that includes the tall- and short-grass prairies of North America, the steppes of Central Asia, and the PAMPAS of Argentina, the temperate grasslands are composed of grasses and associated nonwoody plants.
Found in the equatorial belt, tropical deciduous forest occurs in regions of moderate rainfall. Differences in climate, the frequency of wildfire, and relative abundance of grazing animals contribute to the distinctiveness of these zones.
As the name implies, tropical rainforests occur in regions where temperatures are relatively stable year-round and where precipitation is abundant. Flat, treeless vegetation region separated from a forest by the tree line.
Dry, barren rocks covered by an ice sheet that makes up most of the continent of Antarctica. Paralell of latitude that runs 66.5 degrees north of the Equator.
Flat, treeless vegetation region near the Arctic Circle. Alterations in the layer of air surrounding the Earth, such as an increase of pollution or humidity.
All weather conditions for a given location over a period of time. Hard, spiral structure that is the fruit of some trees.
Type of plant that sheds its leaves once a year. Area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.
Imaginary line around the Earth, another planet, or star running east-west, 0 degrees latitude. Mass of ice that moves slowly over land.
Mass of ice that floats on the ocean but remains attached to the coast. Type of animal that breathes air and has a body divided into three segments, with six legs and usually wings.
People and culture of seven Sioux tribes native to the Great Plains. Animal with hair that gives birth to live offspring.
Female mammals produce milk to feed their offspring. Wetland area usually covered by a shallow layer of seawater or freshwater.
Area of the United States consisting of the following states: Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, and Wisconsin. White liquid produced by female mammals to feed their young.
The area made of the U.S. states of Oregon and Washington, and the Canadian province of British Columbia. Type of tree with a tall trunk, no branches, and a leafy crown.
Permanently frozen layer of the Earth's surface. One of many people and cultures native to the Great Plains in North America.
Organism that produces its own food through photosynthesis and whose cells have walls. Division of a country larger than a town or county.
Area of tall, mostly evergreen trees and a high amount of rainfall. Scientific observations and investigation into a subject, usually following the scientific method: observation, hypothesis, prediction, experimentation, analysis, and conclusion.
Part of a plant that secures it in the soil, obtains water and nutrients, and often stores food made by leaves. People and culture native to Southern Africa.
Plants that grow, bloom, or flower during a specific time of year. Grassland of the Serengeti ecosystem of Kenya and Tanzania.
Type of plant, smaller than a tree but having woody branches. Slant, either upward or downward, from a straight or flat path.
Top layer of the Earth's surface where plants can grow. Flat, grassy area where there are seasonal differences in temperature and precipitation.
Area with distinct plant types, determined by climate, soil, drainage, and elevation. There are five major vegetation regions: forest, grassland, tundra, desert, and ice sheet.
Altitude, soil, and precipitation region in which a plant best survives. Gas such as water vapor or carbon dioxide that is released into the atmosphere by a volcano.
Repeating or predictable changes in the Earth's atmosphere, such as winds, precipitation, and temperatures. People and culture native to the Amazon Basin.