Download Biomes of the World

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Date
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Introduction to Natural Resources
Biomes—Notes—KEY
(**This note guide does not use Managing Our Natural Resources)
Biomes: when abiotic and biotic factors come together.
1. Desert
 Very hot and dry
 Less than 10 inches of precipitation per year
 Cover about 1/3 of earth and growing due to desertification: Expansion of desert when the land loses
productivity because of soil erosion, deforestation, overgrazing, and many other factors
 Have biota adapted to dry conditions
Example: thorny shrubs & cacti, rodents, reptiles, birds
a. Tropical desert (i.e., Sahara)
o Few plants
o Wind-blown surface/sand dunes
o Very hot summers
b. Temperate desert (i.e., Southwestern U.S.)
o Cacti and shrubs
o Rocky soils
o Hot summers/moderate winters
c. Cold desert (i.e., Great Basin of the U.S.)
o Grass-shrub type
o No sand dunes
o Cold winters
o Not enough moisture for trees
2. Grassland
 Moderate precipitation (10 to 60 inches per year)
 Covers about 40% of earth
a. Tropical grassland/savanna (grassland with scattered deciduous trees)
o Hot and dry most of year, abundant rain during wet season
o Fire and drought shape savanna
o Low species diversity
o Large grazing mammals and large predators
b. Temperate grassland
o Moderate to hot summers, cold winters with subfreezing temperatures
o Prairies, pampas, steppes, velds
o Most of these grasslands have been converted to croplands
o Fire shapes most grasslands (results in few trees)
c. Polar grasslands/tundra “frozen desert”
o Very cold and dry
o Tundra—“above the timberline”
o Soil thaws to only 3 feet (permafrost)
o Vegetation—lichens, mosses, grasses, and dwarf shrubs
o Animals—rodents, reindeer, fox
o Migration is adaptation to the cold
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3. Forests
 High rainfall
a. Tropical rainforest
o Non-seasonal—precipitation almost daily (80 inches annually)
o Shallow, poor soil
o High species diversity
b. Temperate deciduous forest
o Seasonal (4 seasons), temperatures below freezing in winter
o Animals—migration, hibernation, or inactivity during cold months
o Deciduous—lose leaves yearly (oak, hickory, maple)
c. Northern coniferous forest
o Long, cold winters—most precipitation comes as snow
o Needles and tree trunks litter forest floor because cold greatly slows decomposition
o Conifer = evergreen (spruce, fir, pine)
4. Aquatic Ecosystems—5 limiting factors control growth
 Salinity (dissolved salt)
o Marine/saltwater ecosystems
o Freshwater
o Mix of freshwater and saltwater = estuaries
 Sunlight penetration
o Euphotic zone—enough light for photosynthesis
o Bathyal zone—twilight (some light penetrates)
o Abyssal zone—no light (night)
 Dissolved oxygen—relates to eutrophication
 Plant nutrients—relates to eutrophication
 Water temperature—determines which species can survive
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