1. Opening: Recap
How can being a vegetarian or even better a vegan help to reduce your ecological footprint?
Taking into consideration everything you just learned about the function of communities, should anything be done about the Zebra Mussel invasion of the Great Lakes? Why and What?
Use your answer sheet to respond to the following questions.

2. Compare and Contrast a food chain and a food web.
What would be the result of the removal of the Hare from the food web? What may be the direct cause of that?

3. Community Interactions: Part II
Succession and Invasive Species

4. Lecture Outline Community Response to Disturbance Succession
Invasive Species
Restoration

5. Resistance and Resilience
Removal of a keystone species and the spread of an invasive species are two of many different types of disturbances that can modify the composition, structure, or function of an ecological community.
Communities are dynamic systems and may respond to disturbance in several ways.
They can show resistance: the community remains stable despite disturbance
They can show resilience: the community changes in response to disturbance but later returns to its original state.
Or, a community may be modified by disturbance permanently and may never return to its original state.

6. Succession
Succession is a series of regular, predictable changes in community structure over time.
Activities of organisms change their surroundings and make the environment suitable for other kinds of organisms.
A climax community is a relatively stable, long-lasting community that is the result of succession. The kind of climax community that develops is primarily determined by climate.

7. Primary Succession
Primary succession begins with a total lack of organisms and bare mineral surfaces or water.
Terrestrial primary succession
A pioneer community is a collection of organisms able to colonize bare rock (e.g., lichens).
Lichens help break down rock and accumulate debris, helping to form a thin soil layer.
The soil layer begins to support small forms of life.
Secondary succession begins with the disturbance of an existing ecosystem.
It is much more commonly observed, and generally proceeds more rapidly than primary succession.

8. Primary Succession Pioneer organisms
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.
Each step in the process is known as a successional (seral) stage, and the sequence of stages is called a sere.
Pioneer organisms

9. Primary Succession Primary succession on land
Climax communities show certain characteristics when compared with successional communities.
Climax communities maintain species diversity for an extended period.
They contain multiple specialized ecological niches.
They maintain high levels of organism interactions.
Climax communities recycle nutrients while maintaining a relatively constant biomass.
The general trend in succession is toward increasing complexity and more efficient use of matter and energy.
Primary succession on land

10. Primary Succession Primary succession from a pond to a wet meadow.
Aquatic primary succession
Except for oceans, most aquatic systems are considered temporary.
All aquatic systems receive inputs of soil particles and organic matter from surrounding land.
This results in the gradual filling of shallow bodies of water.
Roots and stems below water accumulate more material.
Establishment of wet soil.
Primary succession from a pond to a wet meadow.

11. Secondary Succession Secondary succession on land
Secondary succession occurs when an existing community is disturbed or destroyed but much of the soil and some of the organisms remain.
Because the soil and nutrients remain, this process can advance more rapidly than primary succession.
Plants and organisms that survive the disturbance can grow quickly and reestablish themselves.
Nearby undamaged communities can serve as sources of seeds and animals.
The new climax community is likely to resemble the destroyed community.
Grasses and weeds are the pioneers in secondary succession.
Communities continue to change during succession until the final community the ecosystem can support is established. This is the climax community.
If fire maintains the ecosystem then they are called fire climax communities. These communities regenerate quickly and are able to maintain their stability due to moderate, fairly frequent discturbances.
Secondary succession on land

12. Modern Concepts of Succession and Climax
As settlers changed “original” ecosystems to agriculture, climax communities were destroyed.
Many farms were abandoned, and land began to return to its “original” condition.
Ecologists began to recognize there was not a fixed, pre-determined community for each part of the world.
The only thing differentiating a climax community from any other successional community is its time scale.

13. Two Important Theories
Frederick Clements
Henry Gleason
Ecologists have conceptualized communities in different ways
Frederick Clements: a botanists in the early 20th C promoted the view that communities are cohesive.
Members of a community share liming factors and evolutionary histories.
They remain associated over time and space
Henry Gleason: disagreed. Also a botanist
Maintained that each species responds independently to its own liming factors
Members of a community act independently and can respond independently
Associations are temporary and can easily change
Today, ecologists side largely with Gleason, although most see validity in aspects of both men’s ideas.

14. Invasive Species
The first definition, the most used, applies to non-indigenous species, or "non-native", plants or animals that adversely affect the habitats and bioregions they invade economically, environmentally, and/or ecologically. They disrupt by dominating a region, wilderness areas, particular habitats, and/or wildland-urban interface land from loss of natural controls (i.e.: predators or herbivores).
Not all exotic species turn invasive, but most invasive species are non-native organisms that people have introduced, intentionally or by accident from elsewhere in the world.
Species may also become invasive when limiting factors that regulate their population growth are removed.
Ecologists generally view the impacts of invasive species, and introduces species, as over-whelmingly negative.
Some introduced species have provided benefits to our economy.
The European Honeybee pollinates many of our crops

15. Globalization and Invasive Species
The impacts of invasive species has grown with the globalization of our society.
Our global trade helped spread zebra and quagga mussels, which were unintentionally transported in the ballast water of cargo ships.
To maintain stability at sea, ships take water into their hulls as they being their voyage and discharge that water at their destination.
Decades of unregulated exchange of ballast water have carried hundreds of species across the oceans.

16. Environmental Policy Assisting
1990: Congress passed the Non-indigenous Aquatic Nuisance Prevention and Control Act which became the National Invasive Species Act of 1996.
This law directed the Coast Guard to ensure that ships dump their freshwater ballast at sea and exchange it with saltwater before entering the Great Lakes.
Since then, the funding has become available for the control and eradication of invasive species.

17. Zebra Mussel Removal Many techniques were tried:
Removing them manually
Applying toxic chemicals
Drying them out
Depriving them of oxygen
Introducing predators and diseases
Stressing them with heat, sound, electricity, carbon dioxide, and ultra-violet light
Most of these are localized and short-term fixes that are not capable of making a dent in the huge populations at large in the environment.
In most cases, managers are finding that controlling and eradicating invasive species are so difficult and expensive that preventative measures (such as ballast water regulations) represent a much better investment.

18. Restoration
Can we try to restore an altered community to its former condition?
Ecological Restoration
Humans have already forced transformations on natural landscapes through habitat alteration, deforestation, hunting of keystone species, pollution, and other activities.
Invasive species just add to this work we already started.
There are very few pristine areas on Earth so this gave rise to a new conservation effort.
Ecological restoration: the act of research the historical conditions of an ecological community as it existed before our industrialized civilization altered them. Then try to devise ways to restore some of these areas to an earlier condition, often to a natural “presettlement” condition.
Great Plains
US Great Plains being restored to is prairie days before it was converted to agriculture in the 19th century---Planting prairie vegetation, weeding out invaders and competitors, and introducing controlled fire to mimic the fires that historically maintained this community.
Florida Everglades
The world’s largest restoration project is the ongoing effort to restore the Florida Everglades ecosystem of marshes and seasonally flooded grasslands.---flood control practices, water diversions for irrigation and development have dried out the naturally wet region.
It provides drinking water for millions and money for tourists.
The Mesopotamian Marshes
Located between the Tigris and Euphrates Rivers in Iraq, formerly one of the worlds greatest wetlands
The governemtn of Saddam Hussein diverted water from the marshes in an effort to debilitate the minority peoples who had lived there for thousands of years.
Following the U.S. occupation of Iraq, ecologists from many nations joined together to try to restore the marshes and give their human residents a place to live again in their traditional lifestyle.

19. Conclusions
Pg. 155-succession is a stereotypical pattern of change within a community through time.
Pgs Primary succession begins with an area devoid of life. Secondary succession begins with an area that has been severely disturbed.
Pg.158-Clements held that communities are discrete, cohesive units. His view has largely been replaced by that of Gleason, who held that species may be added to and deleted from communities through time.

20. Conclusions
Pgs Invasive species such as the zebra mussel have altered the composition, structure, and function of communities.
Pgs Humans are the cause of most modern species invasions, but we can also respond to invasions with prevention and control measures.