Transcript GEOG 123B Lec. #12

Chapter 20
Terrestrial Biomes
Geosystems 5e
An Introduction to Physical Geography
Robert W. Christopherson
Charlie Thomsen
Final Exam
On April 11 at the Alumni Hall (AH) STAGE.
Will cover chapters 7,15,16,17,18,19,20, and 21.
Will cover all information on the PowerPoint slides.
It will contain 100 multiple choice and T/F questions.
MUST BRING #2 Pencils !!!
Exam will start at 2pm until ~ 4pm. Once you are
finished please leave class quietly.
Know the boldface terms at each chapter.
Review summary questions at the end of each chapter –
most of them I specifically answered in the PowerPoint
presentations.
Key Learning Concepts:
Define the concept of biogeographical realms of
plants and animals and define ecotone, terrestrial
ecosystem, and biome.
Define six formation classes and the life-form
designations and explain their relationship to
plant communities.
Describe ten major terrestrial biomes and locate
them on a world map.
Relate human impacts, real and potential, to
several of the biomes.
2. What is a biogeographical realm? How is the world
subdivided according to plant and animal types?
Biogeographical realms of plants and animals are
geographic regions where groups of species evolved.
From these centers, species migrate worldwide according
to their niche requirements, reproductive success,
competition, and climatic and topographic barriers.
Recognition that such distinct regions of flora and fauna
exist was an early beginning of biogeography as a
discipline. The next two slides (maps) illustrate the
botanical (plant) and zoological (animal) regions
forming these biogeographical realms. Each realm
contains many distinct ecosystems that distinguish it
from other realms.
2. Describe a transition zone between two
ecosystems. How wide is an ecotone?
The transition zone between two ecosystems is called an
ecotone. Boundaries between natural systems are “zones
of shared traits,” therefore they are zones of mixed
identity and composition, rather than rigidly defined
boundaries. A tropical savanna is a good example of an
ecotone. Situated between tropical forests and tropical
steppes or deserts, tropical savanna is a mixture of trees
and grasses. The savanna biome includes treeless tracts
of grasslands, and in very dry savannas, grasses grow
discontinuously in clumps, with bare ground between
them.
3. Define biome. What is the basis of
the designation?
A large, stable terrestrial ecosystem is known as a biome.
Specific plant and animal communities and their
interrelationship with the physical environment
characterize a biome. Each biome is usually named for
its dominant vegetation. We further define these general
biomes into more specific vegetation units called
formation classes. These units refer to the structure and
appearance of dominant plants in a terrestrial ecosystem,
for example, equatorial rain forest, northern needleleaf
forest, Mediterranean shrubland, arctic tundra.
4. Distinguish between formation classes and life-form
designations as a basis for spatial classification.
Interacting populations of plants and animals in an area form a
community, or association of related species. Large vegetation units, the
floristic component of a terrestrial ecosystem characterized by a
dominant plant community, are called plant formation classes. Each
formation includes numerous plant communities, and each community
includes innumerable plant habitats. Within those habitats, Earth's
diversity is expressed in approximately 250,000 plant species.
More specific systems are used for the structural classification of plants.
Such life-form designations are based on the outward physical
properties of individual plants or the general form and structure of a
vegetation cover. These physical life-forms, (see next slide), include
trees (larger woody main trunk, perennial, usually exceeding 3 m);
lianas (woody climbers and vines); shrubs (smaller woody plants;
branching stems at ground); herbs (small plants without woody stems
above ground); bryophytes (mosses, liverworts); epiphytes (plants
growing above the ground on other plants, using them for support); and
thallophytes, which lack true leaves, stems, or roots (bacteria, fungi,
algae, lichens).
5. Describe the equatorial and tropical rain forests. Why is
the rain forest floor somewhat clear of plant growth? Why
are logging activities for specific species so difficult there?
Biomass in a rain forest is concentrated high up in the canopy, that
dense mass of overhead leaves with a vertical distribution of life
that is dependent on a competitive struggle for sunlight. The
canopy is composed of a rich variety of plants and animals. Lianas
(vines) branch from tree to tree, binding them together with cords
that can reach 20 cm in diameter. Epiphytes (a plant that derives
its moisture and nutrients from the air and rain and grows usually
on another plant) flourish there as well. The floor of the rain forest
and the floor of the ocean are roughly parallel in that both are dark
or dimly lit, relatively barren, and a place of fewer life-forms–
although the rainforest floor is much livelier than the sea floor.
Logging is difficult because individual species are widely
scattered; a species may occur only once or twice per square
kilometer.
6. What issues surround deforestation of the rain
forest? What is the impact of these losses on the
rest of the biosphere?
Burning is more common than logging in deforestation because of
the scattered distribution of specific types of trees mentioned
earlier. Fires are used to clear land for agriculture, which is
intended to feed the domestic population as well as to produce cash
exports of beef, rubber, coffee, and other commodities. Every
year, approximately 15.25 million acres are thus destroyed, and
more than 10 million acres are selectively logged. The United
Nations Food and Agricultural Organization (FAO) estimates that
if this destruction to rain forests continues unabated, these forests
will be completely removed by the year 2050!
Another threat to the rain forest biome emerged in the 1990s:
exploration for and development of oil reserves.
7. What do caatinga, chaco, brigalow,
and dornveld refer to? Explain.
Local names are applied to the tropical seasonal
forest and scrub on the margins of the rain forest:
the caatinga of northeast Brazil, chaco area of
Paraguay and northern Argentina, the brigalow
scrub of Australia, and the dornveld of southern
Africa.
8. Why does the northern needleleaf forest biome
not exist in the Southern Hemisphere? What is its
relationship to climate type?
Stretching from the East coast of Canada and the
Maritimes westward to Alaska and continuing
from Siberia across the entire extent of the Russia
to the European Plain is the northern needleleaf
forest, also called the taiga (a Russian word) or
boreal forest. The Southern Hemisphere, lacking
D climates except in mountainous locales, has no
biome designated as such. However, forests of
needleleaf trees exist worldwide at high elevation.
9. In which biome do we find Earth's tallest
trees? Which biome is dominated by small,
stunted plants, lichens, and mosses?
The temperate rain forest biome is recognized by its lush forests at
middle and high latitudes, occurring only along narrow margins of the
Pacific Northwest in North America, with some similar types in southern
China, small portions of southern Japan, New Zealand, and a few areas of
Chile. The tallest trees in the world, the coastal redwoods (Sequoia), are
found in this biome (their distribution is shown on the map in the next
slide). These trees can exceed 1,500 years of age and typically range in
height from 60 to 90 m ,with some exceeding 100 m. Other
representative trees—Douglas fir, spruce, cedar, and hemlock—have
been reduced to a few remaining valleys in Oregon and Washington.
Tundra vegetation is characterized by low, ground-level plants and some
woody plants. Representative plant species are sedges, mosses, arctic
meadow grass, snow lichen, and dwarf willow. They are found in the
arctic tundra -the extreme northern area of North America and Russia,
bordering on the Arctic Ocean.
10. What type of vegetation predominates in the
Mediterranean dry summer climates?
The dominant shrub formations that occupy these
regions are short, stunted, and tough in their ability to
withstand hot-summer drought. The vegetation is
called sclerophyllous (from sclero for “hard” and
phyllos for “leaf”); it averages a meter or two in height
and has deep, well-developed roots, leathery leaves,
and uneven low branches. Plant ecologists think that
this biome is well adapted to frequent fires, for many of
its characteristically deep-rooted plants have the ability
to resprout from their roots after a fire.
11. Describe some of the unique
adaptations found in a desert biome.
Much as a group of humans in the desert might behave with short
supplies, plant communities also compete for water and site
advantage. Some desert plants, called ephemerals, wait years for a
rainfall event, at which time their seeds germinate quickly, develop,
flower, and produce new seeds, which then rest again until the next
rainfall event. The seeds of some xerophytic species open only
when fractured by the tumbling, churning action of flash floods
cascading down a desert arroyo, and of course such an event
produces the moisture that a germinating seed needs.
Desert plants employ other strategies such as long, deep tap roots;
succulence (that is, thick, fleshy, water-holding tissue such as that
of cacti); spreading root systems to maximize water availability,
waxy coatings and fine hairs on leaves to retard water loss; leafless
conditions during dry periods; reflective surfaces to reduce leaf
temperatures; and, tissue that tastes bad to discourage herbivores.
12. What is the relationship between island
biogeography and biosphere reserves?
Describe a biosphere reserve.
Setting up formal natural reserves called biosphere reserves at
continental sites involves principles of island biogeography. Island
communities are special places for study because of their spatial
isolation and the relatively small number of species present. They
resemble natural experiments because the impact of individual factors,
such as civilization, can be more easily assessed on islands than they can
over larger continental areas. It is now known that the number of species
should increase with the size of the island, decrease with increasing
distance from the nearest continent, and remain about the same over
time, even though composition may vary. These considerations are
important to establishing the optimum dimensions for biosphere
reserves. The race is on between setting aside tracts of land in reserves
and the permanent loss of remaining natural biomes.
The goal of biosphere reserves is to preserve species diversity.
End of Chapter 20
Geosystems 5e
An Introduction to Physical Geography
Robert W. Christopherson
Charlie Thomsen
Chapter 21
Earth and the
Human
Denominator
Geosystems 5e
An Introduction to Physical Geography
Robert W. Christopherson
Charlie Thomsen
Key Learning Concepts:
Determine an answer for Carl Sagan's question, “Who
speaks for Earth?”
Describe the growth in human population and speculate
on possible future trends.
List the subjects of recent environmental agreements,
conventions, and protocols and relate them to physical
geography and Earth systems science (geosystems).
Appraise your place in the biosphere and realize your
physical identity as an Earthling.
Analyze the “An Oily Bird” and relate your analysis to
energy consumption patterns in the United States and
Canada.
1. Who speaks for Earth?
Carl Sagan answered his question “who speaks for
Earth” with this perspective:
“We have begun to contemplate our origins:
starstuff pondering the stars; organized
assemblages of ten billion billion billion atoms
considering the evolution of atoms; tracing the long
journey by which, here at least, consciousness arose.
Our loyalties are to the species and the planet. We
speak for Earth. Our obligation to survive is owed
not just to ourselves but also to that Cosmos,
ancient and vast, from which we spring.”
(Carl Sagan, Cosmos, New York: Random House,
1980, p. 345.)
2. What is meant by the Gaia hypothesis?
Just as the abiotic spheres affect the biosphere, so do living
processes affect abiotic functions. All of these interactive
effects in concert influence Earth's overall ecosystem. In
essence, the planetary ecosystem sets the physical limits for
life, which in turn evolves and helps to shape the planet.
Thus, Earth can be viewed as one vast, self-regulating
organism. The hypothesis contends that life processes
control and shape inorganic physical and chemical
processes. The biosphere is so interactive that a very small
mass can affect a very large mass. Thus, Lovelock and
Margulis think that the material environment and the
evolution of species are tightly joined; as the species evolve
through natural selection, they in turn affect their
environment.
3.What factors led to the Exxon Valdez accident?
On 24 March 1989, in Prince William Sound off the southern coast of Alaska, in clear
weather and calm seas, a single-hulled supertanker operated by Exxon Corporation, an
international energy corporation, struck a reef that was outside the normal shipping
lane. The tanker spilled 41.64 million liters of oil. It took only 12 hours for the Exxon
Valdez to spill its contents, yet a reasonable cleanup will take years and billions of
dollars. Because contingency emergency plans were not in place, and promised
equipment was unavailable, response by the oil industry took 10 to 12 hours to activate,
about the same time that it took the ship to empty.
The immediate effect on wildlife was contamination and death, but the issues involved
are bigger than these damaged ecosystems. Many factors influence our demand for oil.
Well over half of our imported oil goes for transportation.
The death toll for animals was massive: at least 3000 sea otters killed (or about 20% of
the resident otters), 300,000 birds, and uncounted fish, shellfish, plants, and aquatic
microorganisms. Sublethal effects, namely mutations, now are appearing in fish. This
latter side effect of the spill is serious because salmon fishing is the main economy in
Prince William Sound, not oil.
Many factors influence our demand for oil. Improvement in automobile efficiency began
in 1975 due to federal regulations. During the 1980's, there was a rollback of auto
efficiency standards, a reduction in gasoline prices, large reductions in funding for rapid
transit development, and the continuing slow demise of America's railroad network. The
demand for fossil fuels was also affected by the slowing of domestic conservation
programs, elimination of research for energy alternatives, such as solar and wind power,
and even the political delay of a law requiring small appliances to be more energyefficient. Conservation plans again were politically blocked in the Department of Energy
in 1990 and early 1991.
3a.What factors led to the Exxon Valdez accident?
In 2001, comparatively inefficient sports utility vehicles
represented more than half of new car sales. These SUVs
are classified as light trucks and are thus exempt from
auto-efficiency and some pollution standards—they burn
more gas to go fewer miles and pollute more per mile
driven and they are involved in a disproportionate share
of accidents. A combination of waste, low prices, and a
lack of alternatives has spurred the demand for
petroleum. In addition in 2002 the U.S. Administration
formally abandoned funding for efforts to make vehicles
more efficient and instead announced an effort to develop
fuel cells for future times. Alternatives such as
conservation, efficiency strategies, solar, wind, and
photovoltaic cells also took budgetary hits.
Worldwide Oil Spills
Movie: “AMERICA'S BIGGEST
OIL SPILL.”
In 1989, the Exxon Valdez ran ashore on a wellknown nautical hazard in Prince William Sound.
Within 48 hours, over 48 million gallons of crude
oil had spewed out into the environment. Can this
happen again? Why did it happen this time? Are
we ready? Actual footage.
End of Chapter 21
Geosystems 5e
An Introduction to Physical Geography
Robert W. Christopherson
Charlie Thomsen