Transcript Old-Growth Forest

A Forester’s View of a Forest
• Vocabulary:
– Old-Growth Forest: a forest that has never been cut
– Second-Growth Forest: has been cut and re-grown
– Rotation Time: the time between cuts
• Foresters group trees into:
–
–
–
–
Dominants: tallest, most common, most vigorous
Codominants: fairly common, sharing the canomy of the forest
Intermediate: forming a layer of growth below the dominants
Suppressed: growing in the understory
• Sites are classified by site quality: the maximum timber
crop the site can produce in a given time
Clear-Cutting
The cutting of all trees in a
stand at the same time.
4 types:
1.
Shelterwood-Cutting:
•
Cutting dead and less desirable tress first and then cutting the mature
trees later. Young trees always left in the forest.
2.
Seed-Tree Cutting:
•
Removes all but a few seed trees (mature trees with high seed production
and good genetics)
3.
Selective Cutting
•
Individual trees are marked and cut
•
•
4.
Example: Thinning is when poorly formed trees are
removed
Example: Sometimes specific size trees are removed etc.
Strip-Cutting:
1. Narrow rows of forests are cut leaving wooded corridors.
Effects of Clear Cutting on
Forest Chemical Cycling
Effects of Clear Cutting on
Forest Chemical Cycling
Effects of Clear Cutting on
Forest Chemical Cycling
Nitrate concentration in streams following logging and
burning of slash (leaves brances and other tree debris =
slash)
Forests, Parks and Landscapes,
Wildlife, Fisheries and
Endangered Species
Plantation Forestry
• Plantation: a stand of single species
planted in straight rows
• Properly managed plantations can relieve
pressure on forests
Sustainable Forest
• Sustainable forests occur when a forest is managed so
that a resource in it can be harvested at a rate that does
not decrease the ability of the forest ecosystem to
continue to provide that same rate of harvest indefinitely.
Two types
– Sustainablity of the harvest of a SPECIFIC resource (timber)
– Sustainability of the entire ecosystem (entire forest ecosystem)
• Three are few examples of sustainablity.
• The “certification of sustainable forestry” developed
where organizations certify forest practices
– This involves:
• Determining which methods appear most consistent with sustainability
• Comparing the management of a specific forest with those standards
– PROBLEM: A series of harvests is necessary to prove
sustainability and the proof therefore lies in the future.
Global Perspectives on Forests
4 Ways Vegetation Can Effect the Atmosphere
thereby influencing the entire biosphere
•
•
•
•
Changing color of the
surface and the amount of
sunlight reflected and
absorbed
Increasing the amount of
water transpired and
evaporated from the surface
to the atmosphere
Changing the rate at which
greenhouse gases are
released from the Earth’s
surface into the atmosphere
Changing the “surface
roughness,” which affects
wind speed at the surface
Deforestation
•
History
–
–
–
•
Forests have been being cut down since times of the Roman
Empire onward
The greatest losses in the present century have occurred in
South America 4.3 million acres a year are being lost since
the year 2000!
Human population growth is the largest cause
Causes
As populations grow we cut for two main reasons
1. Clear land for agriculture & housing
2. For goods, such as lumber, paper, fuel etc.
•
World Firewood Shortage
–
•
63% of all wood produced is used for firewood
Indirect Deforestation
–
Killing of forests due to pollution or disease.
Countries with the Largest
Forested Areas
Note 1 hectare = 10,000 square meters or 2.471 acres
The World’s Forested Area
Forest and Rangeland in the
Contiguous United States
Land use by area
In the late 20th
century 3/4ths of the
commercial forests (in
the lower 48) were in
the eastern US with
70% of the swtimer
volume in the west.
Today however,
sawtimber volume is
shifting eastward
because of plantation
forestry in the
southeast.
Sawtimber volume
Estimated
volume of
harvested
timber.
Parks, Nature and Wilderness
• Why do we want to have parks? What are
their goals? See page 253 for details.
• Wilderness: an area undisturbed by people
• Managing parks for biological conservation
is a relatively new idea. Parks that are too
small or in the wrong shape may not be able
to sustain their species
A Point of Confusion
Edge Effect:
• When forests are being cut or a park is first
established some animals may take refuge
towards the edges.
• This is different than the edge effect we
discussed during habitat fragmentation.
A History of Parks
• 1842 – The first major public park of the
modern area was Victoria Park in Great
Britain.
• 1864 – Yosemite was the first designated
national park in the world.
• 1872 – Yellowstone was established and was
the first park to be called a “National Park”
•A national park not only provides public access but it affords protection of nature.
In the 20th century conservation became the focus of national parks worldwide.
•Additionally keep in mind that a goal of park and nature preserve management is
maintaining biodiversity in national parks for recreation such as hunting.
Please read about a history of parks on page 255 you need to know this!
So you want to save a species?
--Chapter 14--
What does that really mean?
1.
2.
3.
4.
A wild creature in its wild habitat as a
symbol of its wilderness?
A wild creature in a managed habitat, so the species can feed
and reproduce with little interference so we can see it in a
naturalistic habitat?
A population in a zoo, so the genetic
characteristics are maintained in live
individuals?
Genetic material only – frozen cells
containing DNA from a species for
future scientific research?
Traditional Single-Species
Wildlife Management
•
Maximum Sustainable Yield (MSY): The population size that yielded
maximum production
Assumptions
1. The population could be represented by a single number (its total size)
FALSE!
2. The environment is constant (except where humans have created
change) FALSE!
3. Undisturbed by humans a population would grow to its fixed carrying
capacity FALSE!
• Minimal Viable Population: The goal for a threatened or endangered
species. Defined as the estimated smallest population that can maintain
itself and its genetic variability indefinitely.
• Optimum Sustainable Population: The population level that results in
an optimum sustainable yield. The level is in some way best for the
population, its ecological community, its ecosystem or the biosphere
The Logistic Growth Curve
Please read the caption of this image on page 266 figure 14.4 and
summarize in your notes what this graph is trying to say in your
own words. Non-volunteers will be randomly selected to answer.
Classic Cases of Wildlife Management
• The American Grisly (Grizzly) Bear
– Endangered due to hunting & habitat destruction
– Restore to what level? How do we know?
• The American Bison
– Hunter for their hides
– Killed in war against native Americans
– Recovering due in part to ranchers raising them for profit
• A common goal in wildlife conservation is to “restore” the
abundance of a species
• Adequate information of the abundance of a species is very
rare
Improved Approaches to Wildlife
Management
• Time Series and Historical Range of Variation
- Time Series: an estimate of a population over a
number of years
- Historical Range of Variation: the known range
of abundances of a population over some past time
interval
• Age Structure as Useful Information
• Harvests as an Estimate of Numbers
– Catch per Unit Effort: estimates previous animal
abundance. Assumes same effort by hunters.
Whooping Cranes
• Endangered due to
–
–
–
–
Destruction of wetlands
Habitat loss due to urbinization
Agricultural modification of their flyways
All of these things casued the following:
•
•
•
•
Food web disruption
Loss of breeding grounds
Loss of nesting sites
Loss of migration habitat
– Hunted for a variety of reasons
• For goods: feathers, meat, skins, eggs, trophies etc.
• For sport
– Sometimes killed by accident
Whooping Crane Migration route and
Change on Population from 1940 - 2000
Fish & Fishing
• Fish provides 16% of the world’s protein
–
–
–
–
In North America only 6.6% comes from fish
28% in the Far East
22% in Central Asia
21% in Africa
• Fish are especially important in developing countries.
• Fishing is an international trade, but the following countries
dominate:
– Japan, China, Russia, Chile and the US
• The amount of fish harvest from the oceans has increase
dramatically. It has more than doubled between 1960 and
1980 where it rose from 35 million MT (metric tons) to 72
million MT.
• There are an estimated 27,000 species of fish and shellfish in
the ocean.
More about Fishing
•
Most fish come from capture fisheries
–
•
That is they are caught in the wild
Some fishing methods
1. Driftners: nets that are dragged through the water and
catch everything in their path including mammals, nontarget fish, birds etc. These non-target organisms are
called “by-catch” or “by the catch”.
2. Long lining: Using long lines that have bated hooks to
catch fish. Also results in “by-catch” catches.
3. Bottom trawling: Heavy nets are scraped along the
surface of the ocean. This is also indiscriminant and not
only catches everything in its path but it destroys
everything in their path.
Fisheries
• The Decline of Fish Populations
Roundnose Grenadier
Blue Hake
Onion-Eye Grenadier
• Which of these fish are caught for food and
which are caught as “by the catch”?
• Can Commercial Fishing Ever Be Sustainable?
– Past experience suggests that economically
beneficial sustainability is unlikely for most wild
populations
The World’s Major Fisheries
Orange areas are major fisheries. The darker the area the
greater the harvest and the more important the fishery.
Whaling – A History
•
•
•
•
•
•
•
•
•
Early whale hunters killed whales from the shore or
from boats near the shore
11th-12th century boards allowed hunting of whales
from bays and off the coast and then brought them to
shore for processing
In the 19th century whaling became “pelagic” that is
people hunt AND process whales from the open ocean.
This was a product of the industrial revolution.
20th century allowed even more whales to be killed
than in the 19th century resulting in a worldwide
decline of most species of whale.
Attempts to control whaling began in 1924 at the
Convention for the Regulation of Whaling.
In 1931 the Convention for the Regulation of Whaling
was signed by 21 countries. This was the first
agreement on whaling.
In 1946 the IWC (International Whaling Commission)
was established at a conference in Washing DC.
In 1982 the IWC put an end to commercial whaling.
In 2006 a movement in the IWC has been put forth to
control whaling rather than end it.
•Japan, Norway and Iceland are pro-whaling
•Australia, the UK, New Zealand and the US are antiwhaling
Tuna Catch Decline
Fish Catch in the Chesapeake Bay
A Solution?
• Aquaculture: raising of fish and other
aquatic species in captivity. This is already
being done for some species such as shrimp
and salmon where the economic benefits are
high.
• PROBLEM: Accidental release of farmed
fish. This can cause disease and a host of
other problems. Also since many of the fish
raised in captivity are carnivorous… many
are being fed captured fish!