Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Enger & Smith Environmental Science A Study of Interrelationships Thirteenth Edition Unit 4 - Chapter 6, Part 1 Kinds of Ecosystems and Communities David Rude

Kinds of Ecosystems and Communities

Outline  6.1 Succession  6.2 Biomes Are Determined by Climate  6.3 Major Biomes of the World

Succession Communities proceed through is a series of regular, predictable changes in community structure over time. Activities of organisms change their surroundings & make the environment suitable for other kinds of organisms.

Succession Climax community A relatively stable, long-lasting community that is the result of succession. Not always predictable Ecological Succession of the Climax Forest - video video

Succession  Types of factors that determine the kind of climax community Climate Water Substrate/soil Colonizing organisms

Succession  Primary succession Begins with –Total lack of organisms –Bare mineral surfaces or water

Succession  Primary succession (continued) Examples –Volcanic lava flow –Glaciers retreating –Lower of sea level Takes a long time –Few available nutrients for plants

Succession  Secondary succession Begins with –Disturbance of an existing ecosystem. Much more commonly observed Proceeds more rapidly than primary succession.

Primary Succession  Terrestrial primary succession Pioneer community –A collection of organisms able to colonize bare rock –Lichens –Break down rock and accumulate debris –Helps to form a thin soil layer –Soil begins to support small forms of life –May take 100 years to grow as large as dinner plate

Primary Succession Pioneer organisms

Primary Succession  Later Stages Lichen community replaced by annual plants. Annuals replaced by perennial community. Perennial community replaced by shrubs. Shrubs replaced by shade-intolerant trees. Shade-intolerant trees replaced by shade-tolerant trees. Stable, complex, climax community eventually reached.

Primary Succession Primary succession on land Page 111

Primary Succession  Successional (seral) stage Each step in the process of succession  Sere The entire sequence of stages

Primary Succession  Characteristics of climax communities Maintain species diversity for an extended period. Contain multiple specialized ecological niches. Maintain high levels of organism interactions. Recycle nutrients Maintain a relatively constant biomass.

Primary Succession  The general trend in succession Increasing complexity More efficient use of matter and energy

Primary Succession  Aquatic primary succession Except for oceans, most are considered temporary –All receive inputs of –Soil particles –Organic matter from surrounding land –Results in gradual filling of shallow bodies of water

Primary Succession Early stages –In deeper parts only floating plants and algae –As water depth becomes less –Submerged plants establish roots in sediment –Roots and stems below water accumulate more material –Help to trap sediments

Primary Succession As water depth becomes less –Submerged plants establish roots in the sediments –Elodea and algal mats –Emergent plants become established –Have leaves that float on the surface of the water or project into the air. –Water lilies and cattails

Primary Succession Later Stages – Transition to Terrestrial Community –Wet meadow forms –Grasses & sedges that can tolerate wet roots –Sometimes sphagnum moss forms a thick floating mat »Bog –Eventually becomes dryer –Transitions to climax community typical of the area

Primary Succession Primary succession from a pond to a wet meadow. Page 112

Floating Bog

Bog

Rainforest Bog

Secondary Succession  Secondary succession Occurs when an existing community is disturbed or destroyed –Much of the soil and some organisms remain Soil and nutrients allow process to advance more rapidly than primary succession Plants and organisms that survive disturbance can grow quickly and reestablish themselves

Secondary Succession Nearby undamaged communities serve as sources of seeds and animals. New climax community likely resembles the destroyed community.

Secondary Succession  Example of seral stages Annual plants Grasses and biennial herbs Perennial herbs & shrubs Pines Oak & Hickory trees

Secondary Succession Secondary succession on land Page 113

Historical Perspective on Succession and Climax  Original communities that European explorers found: East – hardwood forests North – evergreen forests Central – grasslands South - desert  Early ecologists saw these as the endpoint

Historical Perspective on Succession and Climax  Settlers changed “original” ecosystems to agriculture Poor farming practices destroyed soil When farms were abandoned, began returning to its “original” condition.  New climax forest resembled original Fewer species Sometimes entirely different kinds of communities

Historical Perspective on Succession and Climax New species from other parts of the world changed the mix of organisms Diseases removed species that were formerly dominant –Chestnut blight –Dutch Elm disease

Modern Concepts of Succession and Climax  Not a fixed, pre-determined community for each part of the world. Main difference between climax community and successional community is its time scale. Climate is only one of many factors that determine climax community

Modern Concepts of Succession and Climax Human activities that alter climax communities –Agricultural practices –Logging –Suppression of fire –Changing the amount of water present –Draining an area –Irrigation and flooding

Biomes Are Determined By Climate  Biomes Terrestrial climax communities with wide geographic distributions. Different communities within a biome will show differences in exact species present General structure and the kinds of niches and habitats present are similar

Biomes: Major Types of Terrestrial Climax Communities  Two primary non-biological factors that determine climax communities Temperature Patterns of precipitation –Total amount –Form – rain, snow, sleet –Distribution

Biomes: Major Types of Terrestrial Climax Communities  Major Biomes Rainforest –Tropical –Temperate

Biomes: Major Types of Terrestrial Climax Communities  Major Biomes Forest –Deciduous –Northern Coniferous –Dry

Biomes: Major Types of Terrestrial Climax Communities

 Major Biomes Grassland –Savanna American Prairie

Pampas – South America

Savanna - Tanzania

Biomes: Major Types of Terrestrial Climax Communities  Major Biomes Tundra Caribou Crossing the Tundra

Tundra

Biomes: Major Types of Terrestrial Climax Communities  Major Biomes Desert –Hot –Cold

Northern India

Gobi Desert - Mongolia

Biomes: Major Types of Terrestrial Climax Communities Biomes of the world

The Effect of Elevation on Climate and Vegetation  Temperature Warmest near equator, cooler toward the poles Temperature decreases as altitude increases Moving from sea level to mountain tops –Possible to pass through a series of biomes –Similar moving from the equator to the North Pole

The Effect of Elevation on Climate and Vegetation Relationship between height above sea level, latitude, and vegetation.

The Effect of Elevation on Climate and Vegetation  Other non-biological factors Periodic fires help maintain some grasslands Frequent strong winds prevent establishment of trees Type of soil –Sandy soil dry out quickly –Hinders water demanding species such as trees –Wet soils only allow certain types of trees