AnnouncementsMarch 7, 2011

Exam 1 results are in! Please see your TA if you

want to go over your exam

In discussion this week: Global Climate Change Water Use vs. Distribution

Exam 1 distribution

Mean = 87

Lecture Objectives:

1. Understand Succession2. Learn the characteristics of the

major ecosystems

Types of Ecosystems I & II

Recurring Themes…Terrestrial vs. Aquatic

Type of ecosystem influenced by: rock/soil type temperature precipitation producers/consumers surrounding ecosystems time

Community Properties Abundance -Total number of organisms in

a community.

Diversity - Number of different species, ecological niches, or genetic variation.As a general rule, diversity decreases when

moving from the equator to the poles

Don’t forget, its not only about the number of species but also the number of interactions…

Succession - communities proceeding through predictable changes through time

Succession

Outcome is a climax community- stable, long-lasting community

Two types of succession

Primary - begins with total lack of organisms, bare mineral surface

bssv01.lancs.ac.uk/bs/research/ soilecol/linkgrd.htm

Succession following melting of the Muir Glacier

Primary successionStarts with bare rock, sand, clay, etc.Colonized by pioneer community

First to colonize bare rock Mainly lichens = mutualistic

association of algae or bacteria and fungi

Primary successionAcids produced by lichens, physical, chemical weathering break down rock

Dead organic matter and weathered rock create soil

Primary succession Lichens eventually replaced by small, annual

plants Replaced by smaller perennial plants: herbs and

grasses Replaced by grasses, shrubs, shade intolerant

trees Climax forest composed of shade tolerant trees

“Climax” community is not a preordained set of species

Rate of succession and kind of climax community determined by:

Type of initial substrate Climate

Rate of soil accumulationWater availabilityTemperature

Secondary - begins with destruction or disturbance of existing ecosystem

Primary takes longer than secondary

http://content.lib.washington.edu/mtsthelens/

© Roger del Moral

Mount St. Helens1980 1996

Two types of succession

Secondary successionMain difference from primary succession:

Results from disturbance to “climax” community

- Soil already formed

- Pool of species in soil or nearby that can quickly colonize

Biomes - climax communities with wide geographical distributions

Terrestrial biomes primarily influenced by: Precipitation:

total amount per year seasonal distribution form (rain, snow)

Temperature: range of temperatures seasonal patterns

Other factors: soil type, wind, fire, etc.

Precipitation and temperature influenced by latitude, longitude, and altitude

% IB 105 students who have visited:

Tropical Forest: 26%Prairie or other grassland: 69%Desert: 39%

Major Terrestrial Biomes

Tundra Occurs at extreme northern latitudes, or high elevations (mountain tundra)

Tundra Key characteristics

low precipitation (<35cm)

Permanently frozen soil layer = permafrost

Waterlogged soils common in summer

Low evaporation, permafrost

Short plants dominate Grasses, dwarf birch,

dwarf willow, lichens

Desert Key characteristics

Very little water (<25 cm/year)High evaporationLarge daily temperature fluctuationsSpecies not very denseSpecies have adaptations to hot, dry

environment Plants – small leaves, store water, dormancy Animals – Night activity, conserve water

Common myths about deserts:

•They are nothing but sand

Joshua Tree National Park, CA

Gobi Desert, Asia

Mohawk Dunes, AZ

Common myths about deserts:

•Not much lives there

Burrowing animals, rodents, lizards, snakes

Common misperceptions about deserts:

•They are always unbearably hot

results from over grazing, intense agricultural use, erosion, water runoff, and over heating of soil.

Desertification: change from fertile land to desert.

Boreal Forest Also called taiga,

northern coniferous forest

Occurs in southern Canada, northern Europe, much of Russia

Boreal Forest Key characteristics

Moderate to low precipitation (25-100 cm)

Short, cool summer; Long harsh winters

Spruce and fir, dominant vegetation

Humid due to precipitation and low evaporation, but winter dry because precipitation is snow

Temperate Deciduous Forest Occur in eastern half of U.S., south central

and eastern Canada, southern Africa, Europe, Asia

Temperate Deciduous Forest Key characteristics

Moderate rainfall (75-100 cm), relatively evenly distributed

Warm summers and relatively mild winters

Trees dominant vegetation, type of tree varies geographically

In North America, dominant trees are maples, aspen, oaks, hickories, etc.

Grasslands Occur in temperate

areas Also called prairies

or steppes

Grasslands Key characteristics

Medium precipitation (25-75 cm)

Hot summers, cold to mild winters

Grasses dominant vegetation

Need fire to prevent invasion of trees, release nutrients

Grasslands Key characteristics

Lots of grazing animals Wastes fertilize prairies,

grazing helps keep out trees

Most grassland has been converted to agriculture

Savanna Occurs in Africa,

South America, Australia

Key characteristicsHigh rainfall (50-

150 cm), but unevenly distributed

Periods of high rainfall, followed by droughts

Temperature warm, relatively constant

SavannaKey characteristics

Plants dominated by grasses and drought resistant trees

Dominant animals are grazers

Plant and animal reproduction timed around rainy season, when resources least limiting

Mediterranean Shrublands Also known as

Chaparral. Receives 40-100 cm

annual precipitation.Wet, cool winters and hot,

dry summers. Typical of Mediterranean

coast and coastal southern California.

Mediterranean Shrublands Vegetation dominated by woody shrubs

adapted to hot, dry summers. Fire is a common feature.

Tropical Dry Forest

Annual precipitation ranges 50-200 cm.

Many exhibit monsoon climate. Rainfall highly

seasonal. Drought resistant

plants.

Tropical Rainforest Occur along equator in Central and South

America, Africa, Southeast Asia, Caribbean and Pacific Islands

Tropical Rainforest Key characteristics

Temperature warm and relatively constant

Very high rainfall (>200 cm/year)

Rapid growth, but nutrient poor soils

Multi-layered forests of emergent trees, canopy trees, understory trees, shade-tolerant plants, and epiphytes

Most diverse biome on earth