MST WEEK 8

• Biome


  A large area characterized by its vegetation, soil, climate, and wildlife
• Tundra


  • Extremely cold region that lacks trees and has a permanently frozen subsurface soil (permafrost)
  • Covers expansive areas of the arctic, amounting to 20% of Earth's land surface
  • High winds and low temperatures produce similar plant communities called alpine tundra, on very high mountaintops at all latitudes, including the tropics
• Permafrost


  Permanently frozen layer of soil that restricts the growth of plant roots
• Precipitation in arctic tundra averages from 20 to 60 cm annually, but may exceed 100 cm in alpine tundra</b>
• Winters in tundra are cold, with averages in some areas below -30°C. Summer temperatures generally average less than 10°C
• Tundra vegetation


  • Mostly herbaceous, consisting of a mixture of mosses, grasses, and forbs, along with some dwarf shrubs and trees and lichens
• Tundra animals

  • Large grazing musk oxen (resident)
  • Caribou and reindeer (migratory)
  • Predators including bears, wolves, and foxes
  • Many bird species that migrate to the tundra for summer nesting
• Tundra is sparsely settled but has become the focus of significant mineral and oil extraction in recent years
• Taiga


  The largest terrestrial biome on Earth
• Taiga

  • Annual precipitation generally ranges from 30 to 70cm
  • Periodic droughts are common
  • Some coastal coniferous forests of the U.S. Pacific Northwest are temperate rain forests that may receive over 300 cm of annual precipitation
  • Winters are usually cold; summers may be hot
  • Some areas of coniferous forest in Siberia typically range in temperature from-50°C in winter to over 20°C in summer
• Plants in Taiga

  • Northern coniferous forests are dominated by cone-bearing trees, such as pine, spruce, fir, and hemlock
  • Some conifers depend on fire to regenerate
  • Conical shape of many conifers prevents too much snow from accumulating and breaking their branches
  • Needle- or scale-like leaves reduce water loss
  • Diversity of plants in the shrub and herb layers is lower than in temperate broadleaf forests
• Animals in Taiga

  • Many migratory birds nest in northern coniferous forests
  • Other species reside there year-round
  • Mammals include moose, brown bears, and Siberian tigers
  • Periodic outbreaks of insects that feed on the dominant trees can kill vast tracts of trees
• Although they have not been heavily settled by human populations, northern coniferous forests are being logged at an alarming rate, and the old-growth stands of these trees may soon disappear
• Temperate Grassland


  Biome characterized by grasses and forbs as the dominant vegetation
• Distribution of temperate grasslands

  • The veldts of South Africa
  • The puszta of Hungary
  • The pampas of Argentina and Uruguay
  • The steppes of Russia
  • The plains and prairies of central North America
• Precipitation in temperate grasslands

  • Highly seasonal, with relatively dry winters and wet summers
  • Annual precipitation generally averages between 30 and 100 cm
  • Periodic drought is common
• Temperature in temperate grasslands


  • Winters are generally cold, with average temperatures falling below -10°C
  • Summers, with average temperatures often approaching 30°C, are hot
• Plants in temperate grasslands


  • Dominant plants are grasses and forbs, which vary in height from a few centimeters to 2m in tallgrass prairie
  • Many grassland plants have adaptations that help them survive periodic, protracted droughts and fire (e.g. grasses can sprout quickly following fire)
  • Grazing by large mammals helps prevent establishment of woody shrubs and trees
• Animals in temperate grasslands


  • Native mammals include large grazers such as bison and wild horses
  • Temperate grasslands are also inhabited by a wide variety of burrowing mammals, such as prairie dogs in North America
• Human impact on temperate grasslands


  • Deep, fertile soils make temperate grasslands ideal places for agriculture, especially for growing grains
  • As a consequence, most grassland in North America and much of Eurasia has been converted to farmland
  • In some drier grasslands, cattle and other grazers have turned parts of the biome into desert
• Tropical Forest


  Biome occurring in equatorial and subequatorial regions
• Tropical rain forests

  • Precipitation relatively constant, about 200-400 cm annually
  • High year-round temperature, averaging 25-29°C with little seasonal variation
• Tropical dry forests

  • Precipitation highly seasonal, about 150-200 cm annually, with a six- to seven-month dry season
  • High year-round temperature, averaging 25-29°C with little seasonal variation
• Tropical forests


  • Vertically layered, with competition for light
  • Layers include trees above a closed canopy, canopy trees, sub canopy trees, and layers of shrubs and herbs
  • Broadleaf evergreen trees dominant in tropical rain forests
  • Many tropical dry forest trees drop leaves during dry season
  • Epiphytes like bromeliads and orchids cover trees, less abundant in dry forests
  • Thorny shrubs and succulent plants common in some tropical dry forests
• Animals in tropical forests

  • Highly diverse, including millions of undescribed insect, spider, and arthropod species
  • Adapted to vertically layered environment, often inconspicuous
• Deciduous Forest

  A biome dominated by deciduous trees which lose their leaves seasonally
• Types of deciduous forests

  • Temperate deciduous forests
  • Tropical and subtropical deciduous forests (dry forests)
• Deciduous forests


  • Have broad-leaf trees
  • Trees in tropical deciduous forests lose leaves in dry season and regrow in rainy season
  • Trees in temperate deciduous forests lose leaves in fall and regrow in spring
• Animals in deciduous forests


  • Insects
  • Spiders
  • Reptiles
  • Birds
  • Mice
  • Rabbits
  • Foxes
  • Deer
  • Otters
  • Bears
  • Humans
  • Elephants
  • Monkeys
  • Tigers
  • Giraffes
• Trees in deciduous forests

  • Oak
  • Birch
  • Beech
  • Aspen
  • Elm
  • Maple
  • Teak
  • Palm
  • Bamboo
• Other plants in deciduous forests

  • Flowers
  • Ferns
  • Mosses
  • Herbs
  • Orchids
  • Vines (lianas)
• Temperate deciduous forests


  • Average temperature of 50°F
  • Annual rainfall of 30-60 inches
  • Have precipitation in the form of snow
  • Require at least 120 days without frost
• Tropical and subtropical deciduous forests

  • Temperature range of 68°F to 77°F
  • Annual rainfall can be over 80 inches
• Climate change


  Altering the way deciduous forests respond to temperature, precipitation and drought
• Human impacts on deciduous forests

  • Logging
  • Conversion to agriculture
  • Deforestation for housing
  • Forest fires
  • Farming
• Logging and deforestation have an impact on the forest because humans cut down millions of trees each year for housing construction
• Desert

  • Distribution: Deserts occur in bands near 30° north and south latitude or at other latitudes in the interior of continents (for instance, the Gobi Desert of north-central Asia)
  • Precipitation: Precipitation is low and highly variable, generally less than 30 cm per year
  • Temperature: Temperature is variable seasonally and daily, maximum air temperature in hot deserts may exceed 50°C; in cold deserts air temperature may fall below -30°C
• Desert plants

  • Landscapes are dominated by low, widely scattered vegetation; the proportion of bare ground is high compared with other terrestrial biomes
  • Include succulents such as cacti or euphorbs, deeply rooted shrubs, and herbs that grow during the infrequent moist periods
  • Adaptations include tolerance of heat and desiccation, water storage, and reduced leaf surface area
  • Physical defenses, such as spines, and chemical defenses, such as toxins in the leaves of shrubs, are common
• Desert animals

  • Common desert animals include snakes and lizards, scorpions, ants, beetles, migratory and resident birds, and seed-eating rodents
  • Many species are nocturnal
  • Water conservation is a common adaptation, with some species surviving solely on water obtained from breaking down carbohydrates in seeds
• Human impact on deserts


  • Long-distance transport of water and deep groundwater wells have allowed humans to maintain substantial population in deserts
  • Urbanization and conversion to irrigated agriculture have reduced the natural biodiversity of some deserts