Chapter 6 Major Ecosystems of the World

I. Earth’s Major Biomes

• A. Biome

– 1. A large, relatively distinct terrestrial region with a similar climate soil, plants, and animals, regardless of where it occurs in the world

– 2. Nine major biomes

• B. Location of each biome is primarily determined by:

– 1. Temperature (varies with both latitude and elevation)

– 2. Precipitation

• C. ecotones – the transitional area where two ecosystems meet – called edges – can result from natural boundaries (abrupt changes in soil or rock types), natural disturbances (fires, floods), or human activities (agriculture, land clearing, livestock grazing, timber clearing, roads) – edge communities usually have more diversity than the communities on either side of the ecotone – types of edges

– 1. abrupt edge – abrupt edges between communities with no edge community – changes in rock and soil types, topography, or microclimate

– 2. mixed edges – species from both invade the ecotone and compete for resources

• a. dominant mixed edges – species from one community or the other dominate the edge community

• b. nondominant mixed – species from both communities inhabit the ecotone equally

• D. ecozones (ecoregions) – smaller regions within ecosystems that share similar physical features

• E. Law of Tolerance – describes the degree to which living organisms are capable of tolerating changes in their environment

• F. Law of Minimum – states that living organisms will continue to live, consume available materials until the supply of these materials is exhausted

II. 9 Major Biomes

• 1. Tundra – also know as arctic tundra

– a. Treeless biome in the far north with harsh, cold winters and extremely short summers

– b. Precipitation

• 10–25 cm/yr

– c. Temperature

• Short growing season

• 50–160 days

e. Low species richness

Veg is mostly grasses and sedges – herbaceous plants

Animals – weasels, arctic foxes, snowy owls

f. Very simple food web

g. Low primary productivity

h. alpine tundra – similar ecosystem in the higher elevations of mountains

i. world locations – northern latitudes of North America, Europe, and Russia

– d. Nutrient poor soils with little organic material

• Permafrost present

• Young soils formed from glacier retreat

• 2. Boreal Forests – also known as taiga

– a. A region of coniferous forests in the northern hemisphere

• Just south of tundra

– b. Covers 11% of Earth’s

land

– c. Growing Season

• A little longer than

tundra

– d. Precipitation

• ~ 50 cm/yr

White spruce

Balsam fir

Eastern larch

g. Mostly small animals and migrating birds

h. Some large animals are present

Wolves, bear, moose

– e. Soils are acidic and mineral poor

– f. Vegetation comprised of drought resistant conifers

• 3. Temperate Rainforest

– a. Coniferous biome with cool weather, dense fog and high precipitation

• Ex: Northwest US

– b. Precipitation

• > 127 cm/yr

• Heaviest in winter

– c. Temperature

• Winters are mild

• Summers are cool

– d. Soils are nutrient-poor, but high in organic material (dropped needles) • Cool temperatures slow decomposition

– e. Dominant Vegetation • Large evergreen trees

• Old-growth forest

– f. Variety of cool

climate animal life

– g. Very high species

richness

– h. Heavily logged

• 4. Temperate Decidious Forests

– a. Forest biome that occurs in temperate areas with a moderate amount of precipitation

– b. Precipitation

• 75–150 cm/yr

– c. Temperature

• Seasonality

• Hot summers and cold winters

• d. Topsoil is rich in organic material and underlain by clay

• e. Vegetation is primarily deciduous

– Oak, maple, beech

• f. Animals

– Deer, bear and small animals

• g. Most of this biome land area has been regenerated after farming & timber harvest

• 5. Grasslands

– a. Grasslands with hot summers, cold winters and too little precipitation to support trees

– b. Precipitation

• 25–75 cm/yr

– c. Tall grass prairies

– d. Short grass prairies

– e. 90% of this biome

has been lost to

farmland

• f. Soil has thick, organic material rich organic horizon

• g. Periodic fires keep the dominant vegetation

• h. Animals

– Once covered with bison - no longer true

– Smaller animals are still present (ex: prairie dogs)

• i. world location – North American plains and prairies, Russian steppes, South African velds, Argentinean pampas

• 6. Chaparral – also called scrub forest

– a. Also called a Mediterranean Climate

• Ex: Southern California

• Ex: Greece

– b. Temperature

• Mild, moist winters

• Hot, dry summers

– c. Frequent fires

• d. Soil is thin and often not fertile

• e. Vegetation

– Dense growth of evergreen shrubs

– Lush during the growing season

• f. Animals

– Mule deer, chipmunks, many species of birds

• 7. Deserts

– a. Biome where lack of precipitation limits plant growth

– b. Temperature

• Can very greatly in 24-hr period, as well as yearly (based on location)

– c. Precipitation

• < 25 cm/yr

• d. Soils low in nutrients and high in salts

• e. Vegetation sparse

– cactus and sagebrush

• f. Animals are very small to regulate temperature

• G. world location – 30 degrees north and south of the equator

• 8. Savanna

– a. Tropical grassland with widely scattered trees

– b. Temperature

• Varies little throughout the year

– c. Precipitation

• Seasons regulated by precipitation, not temperature

• 76–150 cm/yr

• d. Soil low in nutrients due to leaching

• e. Vegetation – Wide expanses of grass, occasional Acacia trees

• f. Have fire adaptive

characteristics such as extensive underground root systems

• g. Animals – Herds of hoofed

animals

– Large predators -

lions, hyenas, etc.

• 9. Tropical Rainforest

– a. Lush, species-rich biome that occurs where climate is warm and moist throughout the year

– b. Precipitation

• 200–450 cm/yr

– c. Very productive biome

– d. Most species-rich biome

• e. Ancient, weathered, nutrient-poor soil

– Nutrients tied up in vegetation, not soil

• f. Vegetation

– 3 distinct canopy

layers

• g. Animals

– Most abundant insect, reptiles and amphibians on earth

• h. world location – South America, West Africa, and Southeast Asia

III. Vertical Zonation

• 1. Increasing in elevation has similar effect on ecosystem as traveling to higher latitudes

IV. Aquatic Ecosystem

• 1. Fundamental Division

– Freshwater

– Saltwater

• 2. Aquatic Ecosystems also affected by

– Dissolved oxygen level, light penetration, pH, presence/absence of currents

• 3. Three main ecological categories of organisms

– Plankton - free floating

– Nekton - strong swimming

– Benthos - bottom dwelling

V. Freshwater Ecosystems

• 1. Includes:

– Rivers and streams

– Lakes and ponds

– Marshes and swamps

• 2. Represent 2% of earth’s surface

• 3. Assist in recycling water back to the oceans

Rivers and Streams

• 4. Lakes and Ponds

– a. Body of freshwater that does not flow

– b. Three zones

• Littoral - shallow water area along the shore

• Limnetic - open water beyond the littoral zone

• Profundal - beneath the limnetic zone of deep lakes

– c. Experience thermal stratification (depending on depth)

VI. Thermal Stratification

• a. Temperature changes sharply with depth

• b. Thermocline

– Temperature transition between warmer surface water and colder water at depth

– Only present in warm months

Fall Turnover

VII. Marshes and Swamps

• 1. Lands that shallow, fresh water covers for at least part of the year

• 2. Were once regularly filled in

– More recently their ecosystem services have been better recognized

• Flood protection, water filtering, etc.

VIII. Estuaries

• 1. Where freshwater and saltwater mix

• 2. Highly variable environment

– Temperature, salinity, depth of light penetration

• 3. Highly productive – Nutrients transported

from land

– High level of light

penetrates shallow water

– Plants provide

photosynthetic carpet

IX. Marine Ecosystems

• A. Subdivided into life zones

– Intertidal zone

– Benthic zone

– Pelagic environment

• Neritic Province

• Oceanic Province

Marine Ecosystems

1. Intertidal Zone

• a. Area of shoreline between low and high tides

2. Benthic Zone

• a. Ocean floor, extending from tidal zone to deep sea trenches

• b. Sediment is mostly mud

– Burrowing worms and clams

• c. Three zones

– Bathyal: 200m–4000m deep

– Abyssal: 4000m–6000m deep

– Hadal: 6000m–bottom of deep sea trenches

Left:

Seagrass

Bed

Right:

Kelp Forest

Productive Benthic Communities

• d. productive benthic communities

– (1). Seagrass Beds • Present to depth of 10 m

• Provide food and habitat to ecosystem

– (2). Kelp Forest • 60 m long brown algae found off rocky shores

• Large Biodiversity

– (3). Coral Reefs • Built from accumulated layers of CaCO3

• Colonies of millions of tiny coral animals

• Found in shallow warm water

• Most diverse of all marine environments

• (4). Three types of coral reefs

– Fringing reef - directly attach to continent - no lagoon

– Atoll - circular reef in a lagoon

– Barrier reef - separates lagoon from ocean

• (5) Human Impact on Coral Reefs

– (a). Sedimentation

• From clear-cutting upstream

– (b). Overfishing

– (c). Coral bleaching

– (d). Mining of corals as building materials

– (e). Runoff pollution

3. Pelagic Environment

• a. All the open ocean water

• b. Two main divisions

– (1) Neritic Province

• Water that overlies the continental shelf (to depth of 200 m)

• Organisms are all floaters or swimmers

– (2)Oceanic Province

• Water that overlies depths greater than 200 m

• Organisms are filter feeders, scavengers and predators

J. Human Impacts on the Ocean