Terrestrial Biomes - Class Videosclassvideos.net/111/unit_3/biomes-pdf.pdf · What is a Biome? A biome is a basic ... such as the freshwater, marine, and estuarine biomes. Unfortunately,

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Terrestrial

Biomes Jim Swan

These slides are from class presentations, reformatted for static viewing. The material contained inthese pages is also in the following pages in a narrative formatmore suitable for printing:[Unit 3 Study Guide] [Outline] [The Biomes ] [Succession and Forestry] [Biomes Map/Guide][Mountain Life Zones] [The Soil] [Cryptogamic soil][The Red Cockaded Woodpecker] [Fire Ecology] The links above include relevant content modules for this

material, which is to be tested in the Unit 3 Test. In addition there is a content module on [Hydrology] which is considered Unit 4. However, since this topic relates directly to many of the issuesrelevant to the Terrestrial Biomes, you are to read the Unit 4 module over the next couple of weeks at the end of which you areto take the Unit 4 test online via WebCT. Be sure to note the deadline for taking the Unit 4 Test, which is shown on the syllabusand on the WebCT assignment.

http://envirosci.net/111/111unit3.htmhttp://envirosci.net/111/111unit3outline.htmhttp://envirosci.net/111/succession.htmhttp://envirosci.net/111/biomes/the_biomes.htmhttp://envirosci.net/111/biomes.htmhttp://envirosci.net/111/mountains.htmhttp://envirosci.net/111/cryptogamic.htmhttp://envirosci.net/111/succession/red_cockaded_woodpecker.htmhttp://envirosci.net/111/succession/fire_ecology.htmhttp://envirosci.net/111/water.htmhttp://classvideos.net/111/rm/unit_3/biome001.rm

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What is a Biome?

A biome is a basic type of community, identified by the major plant type.

In this section we are considering primarily the terrestrial, or land, biomes. There are also aquatic biomessuch as the freshwater, marine, and estuarine biomes. Unfortunately, we do not have time to give the aquaticbiomes their just due. However, in Unit 4 on Hydrology certain aspects of these are discussed. The studyof hydrology and water ecology are directly related to the terrestrial biomes and the issues associated withthem. And we will be considering many issues related to both topics throughout this unit.

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The Four Basic Biomes

Grassland

Forest

Desert

Tundra

Each of these is dominated by the plant type inherent in the name, e.g. grasses, trees, plants associated with a desert, or low growing tundra species. But no biome is homogenous, and in each you may find some plants associated with another biome.


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GrasslandIntermediate moisture levels, between that of desert and forest, usually between 10 and 20 per year.

Mid-continental grasslands: e.g. the prairie, Eurasian steppes, pampas in S. America.

Intermountain parks valleys between mountain ranges receive less moisture than mountains.Coastal grasslands conditions not favorable for trees

Californias Central Valley a desert treated like a grassland.

Types of grasslands:

Grasslands tend to be located in the center of continents and on the lee side of mountain ranges where moisture levels have been reduced by the rain shadow effect. (See slide 7) Other conditions can favor grasses over trees. For example, the Serengeti plains cannot support trees due to the hardpan of minerals deposited from ash drifting from the nearby volcano, Ol Doinyo Lengai. Other localized conditions in which the soil is either too wet or too dry may produce grasslands where otherwise there might be a forest.Importance:Fertile soil for agriculture; biodiversity of native grazers and other community members.Threats:Conversion of industrial and urban areas. Soil erosion, salinization.


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ForestForestland is the most diverse of any of the biomes, and has the greatest variation of climates and moisture levels.

Types of forests:Temperate forests: coniferous, deciduous, moist

coniferous, rain forests.Taiga - northern coniferous or boreal forest.

Tropical deciduous, tropical rain forests.Pinyon-juniper woodland. Sometimes called

savanna or interior chaparral.

True chaparral, Mediterranean chaparral.

Importance:Harbors most of the worlds terrestrial biodiversity. Important in climate maintenance.Threats:Conversion to agriculture and urban areas.Deforestation, plantation forestry.


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DesertDeserts may be hot or cold but always have moisture levels at 10 or less per year. Subtropical deserts found between the 23.5

oand

about 30o

north or south latitude, where high pressure prevails and rainfall is suppressed. E.g. Sonoran, Chihuahuan, Mojave.

Rain shadow deserts exist because they are in the lee side (away from the moisture-bearing wind) of a mountain range. E.g. Great Basin desert.

Edaphic deserts exist because of local conditions.

Importance:Harsh environments harbor highly adapted species. May be suitable for agriculture.Threats:Conversion to agriculture and urbanization. Water resource extremely limiting.


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The Rain Shadow

Moist wind

Air rises and coolsDescending air warms producing dry rain shadow on lee side

Moisture condenses

Precipitation occurs mostly on windward side at high altitude.

As moist air reaches topography which increases in altitude, the air cools as it rises. This causes the moisture to condense producing clouds and then precipitation. The precipitation falls mostly on the windward side of the mountain and produces a dry rain shadow on the lee side away from the prevailing wind. This is why the central valley of California (on the lee side of the coast range), the great basin from Nevada to Oregon and beyond (on the lee side of the Sierra Nevada and the Cascade range), and the Great Plains (on the lee side of the Rockies) are deserts or grasslands.


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TundraTundra exists where temperatures are low and the subsoil remains permanently frozen (permafrost). This restricts growth to low shrubs, forbs, and dwarf specimens. Moisture may be high or low (Some tundra qualifies as desert). Harsh conditions may also prevent tree growth.

Arctic tundra found in the region of the arctic circle and nearby where conditions are harsh.

Alpine tundra found at high altitude above treeline.

Importance:Area of pristine habitats (e.g. ANWR), Oil resources. Threats:Highly adapted habitat is also highly vulnerable. Soil erosion, pollution.


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Conditions Which Determine Location of the Biomes

Latitude proximity to the equator determines average temperature and day length. Increasing distance from equator produces more extremes in temperature and photoperiod.

Wind and ocean currents ocean currents determine the temperature of the water, and in turn the temperature of moisture-bearing winds.

Average temperature as well as temperature extremes, photoperiod(length of daylight) and its seasonal variation, moisture and its distribution, as well as local conditions of topography and physiography all these contribute to the formation of a particular biome in an area.


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Latitudinal DifferencesTropics between 23.5 north or south latitude. Little variation in temperature and photoperiod, either day-night or seasonal. Exceptions: altitude effects.

Subtropics between tropics and about 30 degrees. High pressure prevails, especially during summer.

Arctic 58.5 degrees north, the point at which 24 hour days or nights are experienced.

As you go from south to north in the northern hemisphere (or north to south in the southern hemisphere) you find decreasing average temperature, but increasing temperature extremes; and increasingseasonal extremes of photoperiod (day length) as well.


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Wind and Ocean Currents

Cool moist air

Warm moist air

A major determinant in the development of biomes is the presence of moisture. For the western U.S. moisture is mostly derived from the Pacific ocean. Cool water currents coming down from the arctic make the Pacific a cold water ocean for the US. As this cool moist air moves inland it creates fog and rain from northern California northward, and it generally evaporates or is directed away from the hot high-pressure regions of the southwest. This produces the fog and rain forests of the northwest, and the subtropical deserts of the southwest.In the east, moisture wraps around the prevalent high pressure system and produces the rainy, muggy conditions typical of the southeastern US.


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Biomes of North AmericaT

B

TD

SE

A

SA

PJDC

CH

MC

GB R

TR

SN CU

MH

G

Churchill

E

Click on the following or map image to view image and brief description: [T=Arctic Tundra, Pack Ice] [T=Arctic Tundra] [Churchill] [B=Boreal Forest ] [Taiga] [A=Alpine Tundra] [SA=Subalpine] [TR=Temperate Rain Forest] [CH=Chaparral] [TD=Temperate Deciduous] [SE=Southeastern Pine] [E=Everglades]Click on map letter above to view slides for each region. [Key to the Biomes]

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Climate Zones

This graph illustrates the types of biomes produced by differentcombinations of temperature (x axis) and precipitation (Y axis). Note that it is possible to find techinical deserts in almost every temperature range if moisture levels are low enough. In fact the tundra is often a virtual desert due to the low moisture received. Tundra may be snow and ice covered, but it actually receives very little new moisture from year to year.


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Ecological Succession

- a series of predictable changes in the physical and biological components of a community which leads to the development of a climax community.

Climax community the community which makes best use of available resources.

Ecological succession is the natural and predictable process of change in the community. It results from the effects of the biota on the physical environment, which in turn produces conditions which may favor achange in the biota. In this way, for instance, a swamp becomes a meadow, which becomes a forest. The stable ultimate community ofthis process is known as the climax community.


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Primary vs. Secondary Succession

Primary succession succession built upon barren terrain.

e.g. volcanic land, newly exposed land

Secondary succession succession which occurs in a community which has been altered.

e.g. after fire, flood, windstorm, timbering, etc.

The original process by which communities develop on barren terrain is called primary succession. We can see primary succession occurring only where new terrain is exposed by the retreat of glaciers, or the deposition of rock by a volcano. Otherwise, the communities we observe are climax communities. Climax communities do change gradually, and their recovery after disturbance is called secondary succession.


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Plants

The graph seen here illustrates succession as it occurs from barren terrain, and leading to the establishment of a climax forest. Naturally, a desert, tundra, or grassland would be the climax under appropriate conditions. We are using the forest climax in order to understand issues of forestry, endangered species such as the spotted owl, and fire policy. Click on each of the following to view image and text associated with that stage of succession: [Pioneers: Lichens] [Pioneers: Cryptogamic soil] [Weeds and Grasses] [Shrubs] [Early Trees] [Late Trees]


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Forest Succession

20 yrs. Early trees

65 yrs. Late trees

200 yrs. Old growth

This graph illustrates the time it takes from the beginning of succession to reach the peak of each of the stages shown. Weeds and grassesoccur first, then in about 20 years the early trees reach their peak. They are succeeded after about 45 more years by the late trees, etc. Old growth is a forest with a preponderance of trees 200 or more years old.


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Basic Characteristics of Succession

1) Autotrophic Heterotrophic

2) Herbivores Carnivores

3) Simplicity Complexity

Succession results in a change from mostly autotrophic organisms to the normal mixture of autotrophic and heterotrophic organisms seen in typical ecosystems. Succession of heterotrophs begins with herbivores who can eat the autotrophs and adds more and more carnivores who can eat the herbivores. And succession tends to produce ever more complex communities, as each level builds upon, but does not completely replace, the previous level. Old growth communities are usually the most complex communities, but there are some exceptions.


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Primary Succession on Volcanic Land

e.g. Krakatoa in the Indonesian archipelago erupted in 1883.

Rakata remains of original Krakatoa, old growth rain forest has recovered in 100+ years.

Ujung Kulon mainland area swamped by tidal wave from eruption.

Ana Krakatoa son of Krakatoa, emerged from ocean in 1920s example of primary succession.

These are the components of the Indonesian archipelago called Krakatoa which experienced a series of volcanic eruptions, the most dramatic of which occurred in 1883. Since then biologists have been able to observe and chronicle the events in the recovery of the various areas, each of which suffered differently from the event.

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Ecological Succession

Forestry or other disturbance sets succession back to the weed, grass, or shrub stage.

When disturbance such as fire or forestry re-sets a climax forest back to the earlier stage of grasses and weeds. The community must go through succession again in order to reform a climax forest, and will unless changes in the physical environment dictates a different result.


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Productivity & Diversity in Succession

Stages of SuccessionDiv

ersi

ty o

r Pr

oduc

tivity

Lev

elCommercial Productivity

Diversity

Young, mature forestClimax forest

Moist forests

Dry forests

2) Pine forests loose diversity unless

replenished by physical means such as fire.

1) Moist coniferous and rain forests maintain their diversity

through biological turnover.

There is a basic conflict between the uses man has for the forest and the nature of forest succession and its importance to the community. Man has no use for old growth. His desire to cut down old growth is to remove the old rotting trees and replace them with hybrid varieties which will mature in 50 to 65 years to be cut again. This is when the commercial trees are at the mature stage for cutting. Any longer and they will begin to rot and lose commercial value. But it is exactly this development which provides diversity for the community and its value as a habitat for may species. (1) Moist coniferous and rain forests maintain their diversity through biological turnover. (2) Pine forests loose diversity unless replenished by physical means such as fire.


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Biological Legacy(Mt. St. Helens Video)

Biological legacy refers to the characteristics which enable an ecosystem to sustain itself and to recover from disturbance.

Natures mess: downed logs, organic matter

Oases and protected areas

Heterogeneity - a mix of conditions

Flora and fauna insects, soil organisms, nurse species

The class will watch a video showing the recovery of Mt. St. Helens after its May, 1980 eruption. Man creates large scale disturbance through mining and timbering operations. Understanding how nature recovers from disturbance could allow man to reduce his impact and enhance the natural recovery process. One ideal which has come out of such study is the concept of biological legacy, those factors left from the original ecosystem which will enhance, or even be necessary for its recovery.


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Forestry Methods

Uneven aged management methods which result in a variety of ages and types of trees.

Shelterwood management a series of cuts over several decades which results in a forest with some diversity of ages and tree types.

Seed tree management one cut which leaves a few old seed-producing trees.

Selective cutting cut only trees of specific types and ages, leaving the rest.

Selective cutting is ecologically sound, but not cost effective. To produce the same amount of timber much more forestland is required. In addition, since road construction and pollution from men and machinery produce the most impact, this produces much damage unless manual methods are used. Other methods shown can produce more timber on less forest. However these methods are not often used in the Pacific Northwest where most significant old growth is found.


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Forestry MethodsEven-aged management produces a forest of uniform ages and type of tree.

Clear cutting cut everything and replant with uniform type of tree, usually Douglas fir.

This results in a plantation forest, and is called type conversion by the timber industry.

This results in a plantation forest, and is called type conversion by the timber industry.

Even-aged management is the least ecologically sound but the most economically efficient.


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Edge Effects

Traditional forestry leaves fragments of uncut producing many edges along roads and cut lands.

This causes increased erosion, exposure to pollution, insects, fire, and disease.

The primary detrimental effect of forestry, besides elimination of the old growth, diverse forest, is the damage resulting from road construction. The main effects are edge effects, the result of the forest edges along roads and cutover land, and fragmentation, the result of reducing the forest to small "islands" of diversity. Edges make it easier for insects, diseases, and fires to travel. All of these are natural factors, but usually impact small areas of forest. When they move along edges much more forest than normal is affected.


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Forest Fragmentation

Fragments of old growth forest loose diversity due to their isolation.

Island biogeography study of how isolation affects community ecology.

Diversity of isolated habitats decreases with:

decreasing size of contiguous area.

increasing remoteness of similar habitats.

Fragmentation reduces the forest to islands which are too small to support many species. Even when the total area of these islands is substantial, it is the contiguous (connected) area which is important. Species need large areas to establish territories, find mates and other resources, etc. Both area and remoteness are important in the ability of forest and other habitats to maintain diversity.


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Southern Appalachian Corridors

The solution to fragmentation is to not produce small fragments in the first place by cutting in ways the leave large contiguous areas of habitat. It is also possible to retro-fit forests with wildlife corridors. These have been shown in New England and elsewhere to facilitate recovery of many species which had nearly disappeared.


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Canada-US Corridor

Glacier Park

Waterton Lakes NP

Crowsnest Pass

Canada-US Corridor for Grizzly and

Wolf Migration

Grizzly migration

Another corridor system under construction is at Crowsnest Pass in the Northern Rocky Mountains. This is a primary route for grizzlies and wolves who move between the Canadian Rockies and Glacier National Park in the US. The Trans-Canadian Highway crosses the Rockies at Crowsnest Pass and many bears and wolves come into conflict with man and a number are hit by cars and killed. The corridor would reroute the highway to an area away from the primary migration route.


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Cougar Corridors in California

In California cougars often come into contact with people where their usual routes between territories take them near populated areas. The established cougar linkages are shown in this map. Efforts are being made to protect these routes and keep them isolated from human trails and habitation to avoid conflict.

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The Red-cockaded Woodpecker:A good example of the effects

of forest fragmentation.

Life History: Red-cockaded woodpeckers live in extended family groups known as clans or colonies. All members of the clan help incubate and feed the young. Red-cockaded woodpeckers eat various insects, spiders, and other invertebrates found under bark and in the dead limbs of trees. See the page on [The Red-cockaded Woodpecker: A Study in Forest Fragmentation]


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Red-cockaded Woodpecker Habitat

"Candle Trees" Identify Red-Cockaded Woodpecker Colonies

Nesting and roosting cavities are made only in living pine trees over 60 years old, often trees with red-heart disease. Fire plays an important part in maintaining red-cockaded woodpecker habitat by eliminating hardwood undergrowth.


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Prescribed Fire

Ideal colony sites are located in park-like stands of pines with little or no understory growth. Controlled or "prescribed" burns serve to maintain the pine woods by killing off competing shrubs and deciduous trees.

The Southeastern Pine Forest is maintained by the natural fire cycle, burning typically every 8 to 10 years. These fires keep the competitive hardwoods from taking over the pine forest. So fire in this situation keeps the forest from going to climax, which would be hardwoods, and maintains the diversity necessary to sustain species such as the Red-Cockaded Woodpecker. See the page on [Fire Ecology]


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Scientific Monitoring

A biologist from Eglin Air Force Base is part of a survey of red-cockaded woodpeckers and their habitat.

The historic distribution of the red-cockaded woodpecker included the southeastern United States. Several of the twenty or so large areas where the woodpeckers can still be found are on military bases, such as Eglin Air Force Base in the Florida panhandle.

The presence of military bases in sensitive habitat has benefited wildlife, both through land preservation, and also through scientific study.


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Banding of Red-cockaded Woodpecker

A biologist attaches a band to a red-cockaded woodpecker as part of a study of their population and habitat.

Birds are banded to keep track of their movements and estimate their populations. As new birds are captured, those already banded arenoted and, together with knowledge of the number of banded birdsreleased, this allows biologists to extrapolate their population size.


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Southeastern Pine Forest

Pine flatwoods in northern Florida. These longleaf pines grow in a variety of soils, with an understory of saw palmetto.

Pine flatwoods are incredibly flat, and can be sandy or wet. Saw palmetto, one of two palms native to the southern US, is the dominant understory shrub.


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Longleaf Pine Seedling

The seedling of the longleaf pine, called its "grass stage", is adapted to fire and may persist for up to 6 years.

This longleaf pine seedling has been burned. But these seedlings are resistant to fire, and it will survive to grow into a mature pine tree. hardwood shrubs which compete with the pines have been burned away.


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Young Longleaf Pine Sapling

Longleaf saplings are susceptible to fire. But within one to two years they reach a height at which its lowest branches will be high enough to survive routine ground fires.

This longleaf pine sapling would be burned and killed by fire. But it is only vulnerable for about a year, until it is tall enough with limbs high enough off the ground that the small ground fires will not harm it.


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Recent Burn

Regular surface fires keep shrubs and oaks from choking out the pines. Controlled burns are used to maintain the pine forest dominance. Saw palmetto and wiregrass recover quickly.

In this recently burned area, the hardwoods have been removed, the pines survive, and the saw palmetto are recovering.


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Thick bark on mature ponderosa pines lets them survive fire with only scars.

Ponderosa Pine Forest

Ponderosa pines are also resistant to fire. Evidence shows that old trees have been exposed to repeated fires over the years, some possessing large fire scars such as seen here.


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Lodgepole Pine Forest

A lodgepole pine forest is naturally adapted to fires. The pines' serotinous cones have a waxy coating which opens in response to the heat of the blaze, scattering seeds onto soil newly fertilized by nutrients in the ash.

80% of the forest in Yellowstone National Park is lodgepole pine, trees which naturally reseed after a fire. The yellowstone forest is recovering well from the intense fires of 1988.


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Lodgepole Pine Recovery

Soon young seedlings appear and in a few years begin to carpet the forest floor, along with fireweed, lupine and other early stages of succession.

In this way the forest replaces itself and maintains heterogeneity and diversity by constant turnover.

Recovery is generated by the release of seeds from serotinous cones a few days after the fire is over. The ash provides minerals for sustained growth.


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1988 Yellowstone Fires

Although summer fires have always been common in the dry westernforests, 1988 saw the beginning of a period of intense fires in very public places. First Yellowstone, later Yosemite, Colorado, and throughout the west, including, of course, Los Alamos and other areas in New Mexico.These fires have fueled a much needed debate over fire policy and management practices in our forests and other public lands.

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Fire adapted forests:Southeastern pine: longleaf, slash, yellow, loblolly

Sand pine serotinous cones facilitate reseeding

Lodgepole pine serotinous cones

Ponderosa pine thick bark

Chaparral resinous plants burn quickly but roots survive.

Sequoia gigantea very thick bark

Fires reduce competitors.

These forest types all depend on fire in one way or another. If they resist fire, then fire keeps out competitors and prevents the forest from changing to another type. If they burn easily then they recover quickly, and again fire maintains their dominant structure.


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Threatened Frontier

Forests in America

Least at risk

Most at risk

Too late!

Tongass National Forest, Alaska Clayoquot Sound,

Vancouver, B.C.

Glacier National Park

Greater Yellowstone Ecosystem

Mathias Colomb First Nation Lands,

Manitoba

Forests of the Darien Gap

North Cascades National Park, WA

Frontier Forests are forests which haven't been timbered or otherwise significantly impacted by man. Most forests in North America, and throughout the world, are second growth or have been significantly degraded. But Frontier Forests are pristine, and the ones shown here are threatened with degradation. Mouseover each one to see what the threats are..


Tongass National Forest

Forest type: Temperate

Location: Alaska,

Threat: Logging

At risk: One of the world's largest tracts of temperate old growth forest, as well as a unique ecosystem type: coastal temperate rainforest

AdministratorFile Attachmenttongass_national_forest.htm

Clayoquot Sound


Location: Vancouver Island, British Columbia

Threat: Logging. Forest management practices have significantly detracted from the "naturalness" of this area.

Logging within watersheds has negatively impacted the fish stocks and clam beds in the area, which are the main economic support for many of the aboriginal communities.

At risk: The temperate rainforests of Alaska and British Columbia represent half of the world's remaining temperate rainforest. Only one third of Clayoquot Sound is protected including several pristine old growth watersheds and many bog forests. Home to three aboriginal communities: Ahousaht, Hesquiaht and Tla_o_qui_aht.

AdministratorFile Attachmentclayoquot_sound.htm

Mathias Colomb First Nation Lands

Forest type: Temperate,

Location: Manitoba, Canada

Threat: Logging, mining, development

Mathias Colomb First Nation Lands

Forest type: Temperate,

Location: Manitoba, Canada

Threat: Logging, mining, development

AdministratorFile Attachmentmathias_colomb.htm

North Cascades National Park and surrounding areas Forest type: Temperate Location: Washington state, British Columbia Threat: Habitat fragmentation due to logging, overgrazing, and recreational development around the park. At risk: The area represents one of only four frontier forest sites in the lower 48 states of the U.S.

AdministratorFile Attachmentnorth_cascades.htm

Glacier National Park and surrounding forests and wilderness areas Forest type: Temperate

Location: Montana and Alberta, BC Threat: Habitat fragmentation, recreational development, oil and mineral exploration, air/water pollution, logging.

At risk: One of only four remaining forest frontier sites in the lower 48 states of the U.S. It is the only location within the 48 contiguous states in which all native predator populations occur naturally: grizzlies, wolves, and mountain lions

AdministratorFile Attachmentglacier.htm

Greater Yellowstone Ecosystem


Location: Montana, Wyoming, Idaho

Threat: Logging, mining, ski resort development, elk and bison management problems.

At risk: One of the two remaining ecosystems in the lower 48 states where there is still a significant population of grizzly bears and one of only four remaining frontier forest sites in the lower 48. The area also provides habitat for North America's largest herds of elk and free_roaming bison. Also re-introduced wolf population

AdministratorFile Attachmentyellowstone.htm

Forests of the Darien Gap Forest type: Tropical Location: Panama and Colombia Threat: Logging, other wood removal, proposed highway construction, and coca cultivation.

At risk: A proposed highway across the Darien Gap would provide a route for non-indigenous species, such as organisms that cause hoof-and-mouth disease, with potentially disastrous long term biological and economic consequences to both regions. Road construction, logging, and other activities threaten forests that are home to three indigenous cultures and rich native biodiversity.

AdministratorFile Attachmentdarien_gap.htm

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Talamanca Mountains in Costa Rica

The Nature Conservancy, Spring 2002

The Talamanca Mountains are a success story in preservation, at least for now. Threatened by offshore oil drilling and the onshore spoilage that would occur, and by agricultural operations which would turn the rain forest into plantations, the Talamancs have won the latest battle against development. Through efforts of Bio Gems the offshore drilling has been blocked. And with the help of The Nature Conservancy farmers are increasingly using sustainable cultivation techniques which do not destroy tropical forest. An example is the encouragement of shade grown cocoa production, rather than the usual plantations which rely on slash and burn. Shade grown cocoa coexists with the native trees and the biodiversity they sustain. The Conservancy works with farmers to help finance these projects and to find markets for the organic chocolate they produce.


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To follow the source of an organic chocolate bar,

follow the Yorkin River from its mouth on Costa Ricas Caribbean coast

upstream to the commercial town of Bribriand finally over boulder-

strewn rapids to the forested slopes of the

Talamanca Mountains.

Shade-grown cacao (pronounced k-cow) trees produce large pods like these.


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Clearing for agriculture leaves only remnants of a highland forest in Costa Ricas Talamanca Mountains.

Traditionally grown (non-shade) cacao trees require clearing the tropical forest, which then no longer supports the forest community.


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Baltimore orioles are among the many migratory

species which thrive in Costa Ricas forest.

Shade grown cacao gives year-round residents as well as migratory

species the habitat they need.

Baltimore orioles and toucans are among the many residents and migrants supported by preservation of Talamanca's tropical forest.

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The Nature Conservancys EcoEnterprises Fund provides market know-how to boost compatible agriculture such as that practiced by cacao growers in Talamanca.

The cacao pods are split to reveal the beans inside. These will be roasted to produce cocoa powder used to make chocolate.


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Workers on a Chiquita plantation in Costa Rica cut banana bunches which weigh about 70 pounds then hand them on hooks connected to a system of overhead tracks. The train of bananas is pulled to a processing center where the fruit is washed, sorted and packed in boxes.

We make banana growers an ally in conservation rather than an enemy. Wed rather change the entire industry 40% than a few farms by 100%. Weve inoculated the industry in a good way.


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We make banana growers an ally in conservation rather than an enemy. Wed rather change the entire industry 40% than a few farms by 100%. Weve inoculated the industry in a good way.

The Nature Conservancy is not an extremest group. Instead it prefers to work on practical solutions which farmers can accept and which will benefit the natural world.


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Other Ways to Sustainably UseTropical Forests

If you look on your grocers shelf, especially one which specializes in organic and environmentally friendly products, you can find manyproducts such as this which utlize tropical forests in a sustainable way.


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Alternative (Sustainable ) Forestry

Forestry practices which enable the continuation of both forests and wood production.

1) Recognizing the non-timber value of forests:

Watershed

Fishery

Wildlife

Recreation

biodiversity

Sustainable forestry depends upon recognizing that the forest is more than just a collection of trees which can be harvested by man. For that purpose a plantation is all that's needed. But a forest is an ecosystem, with all of its components intact and working together. Recognizing that a forest ecosystem is important for producing clean water, intact fisheries, healthy wildlife populations, and diversity of all biota. Plantation forests don't provide these values. Sustainable forestry is the use of methods which maintain the forest with its natural values, and allows reasonable resource extraction.


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(contd.)2) Mimicking natures methods of increasing diversity. mimicking natural disturbances such as fire, wind, etc.

maintaining and protecting habitat diversity.

cutting methods which maintain diversity.

3) Recycling wood and fiber products.

4) Alternatives to wood products.

Biological legacy tells us that the forest does sustain natural disturbances. If man's disturbances mimic those of nature, and we preserve the important elements of biological legacy, the natural forest can recover successfully and sustainably from those disturbances as well. Even so, using sustainable forestry will result in less wood in the short run than the usual methods. (The fact that the usual destructive methods are not sustainable, and eventually we will have neither forests nor wood escapes most timber industry managers.) In order to have sustainable forestry we will need to reduce our use of raw wood products, and find alternatives for them.

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Grassland vs. Forest Soil

Litter = raw organic matterGrassland Forest

Humus - decaying organic matter

Mineral soil - the parent material infused with minerals from above.

1. Humification - the biological process which creates humus. It is rapid in calcified soils, slow in podsols.

Calcified soil, alkaline, rich in organic materials, retains minerals.

2. Mineralization - final biological breakdown of organic to inorganics: rapid in podsols, slow in calcified soils.

Podsols, acidic, relatively infertile soil, looses minerals to leaching.

1

2

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Soils produced in grassland biomes differ greatly from those present in forests. Grassland soils are produced by the decompositon of grasses, as well as periodic fires which release minerals, and repeated desposition of dung. The result is a calcified soil, slightly alkaline, rich in organic materials such as humus, which retains minerals for the shallow-rooted grasses which depend on them. The soils produced have little raw litter because it is decomposed quickly into organic humus. This humus builds thick layers because it is not mineralized rapidly in these conditions. Forests in comparison release acidic leaves and needles which produce soils called podsols, which are acidic, and relatively infertile soils because they loose minerals to leaching. The minerals leach into the subsoil or mineral soil, which is fine for trees, which have much deeper roots. But it is poor soil for agriculture, containing little humus. Unfortunately deforestation to produce agricultural land is common throughout the world as rich and fertile soils are depleted and overused. See also [The Soil] and the [Prairie Diorama].


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Deciduous and Coniferous Forests

Coniferous forest soils have more litter, less organic humus, and are more acidic than deciduous forest soils. This produces slow humification, but allows minerals to be quickly leached from the soil.

Coniferous forest soils are the most acidic due to the nature of the needles they shed, with the leaves of deciduous trees just slightly less acidic. The acidity of these forest soils reduces the rate of humus production, but speeds the release of minerals into the subsoil and through leaching into the drainage water. This is reflected in the relatively thick layer of raw litter, and the thin layer of humus beneath.


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Grassland SoilGrassland soils are enriched by 1) fires which return mineral ash to the soil, and 2) deposition of dung from grazers. These produce a slightly alkaline humus. The major molecule in humus, called humic acid, acts as a chelating agent to bind reversibly to minerals in the soil, preventing them from leaching from soil, yet making them available for use by plants.

Grassland soils have little raw litter because the litter breaks down quickly into organic humus in the slightly alkaline calcified soils (humification is rapid). The organic humus does not readily loose its minerals to the mineral soil below (mineralization is slow) due to these calcified conditions.


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Tropical Forest Soil

Minerals in tropical forests are almost entirely present in the living vegetation. As soon as vegetation dies it is decomposed and the minerals quickly taken up again by the plantlife. For this reason the soils themselves are very infertile, although the vegetation is often lush. Iron and aluminum compounds in some tropical and subtropical soils complex when dry to form impenetrable soils called laterite.

Tropical forest soils are notoriously poor in humus and are among the least suitable for agriculture. This is because virtually all the nutrients are in the standing vegetation. Decomposition (both humification and mineralization) is extremely rapid and soon after vegetative matter falls to the ground it is broken down and its minerals are taken back up by the plant life. Man has been able to utilize these soils to eke out a living by the technique of "slash and burn". In this technique the forest vegetation is burned to release the minerals into the soil. This soil can support one season of intensive agriculture. The next year something less demanding on the soil must be grown, and the following year the land is allowed to lie fallow. This land may be productive again in another decade. But the natural diverse forest never recovers. The people move on to slash and burn another plot. And if the soil is lateritesoil, a type containing iron and aluminum compounds, it may become unworkable when exposed to the sun and dry.


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Desert Soils

Desert soils tend to not have much humus due to the low rate of plant growth, but their soils usually have minerals and tend to be alkaline. This makes them fertile when provided with sufficient water for growth. Dry land irrigation produces a significant proportion of fruits and vegetables, putting stress on water resources.

Desert soils are poor in humus too, but because they are slightly alkaline they don't form laterite and they don't loose the minerals to leaching. So, with enough water, they can be quite productive asevidenced by large farming operations in California and throughout the Southwestern U.S. The problem, of course, is what the demand forwater does to this resource in terms of depletion and salinization.


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Desertification:

The creation of desert-like conditions in previously arable or marginal land.The Sahara Desert

The Sahel

When land that is arable but marginal (it is productive but is in an area which is semi-arid and subject to drought) the slightest change can tip the balance. This often occurs when additional pressure is put on the land by grazing or deforestation. Grazing can cause the land to dry out and erode due to loss of vegetative cover. So can cutting trees. The result is that the land becomes more arid and may loose its ability to support agriculture. An area where this has occurred extensively is the Sahel, a band of semi-arid land between the Sahara desert and the forests to the south. As population pressure has forced the overuse of the land it has become dry and unproductive. But this process isn't restricted to the Third World, and occurs in parts of the US andelsewhere when land is overgrazed and deforested.

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Salinization- the buildup of salt from irrigation or fertilizer use. This eventually reduces soil fertility and may cause the land to cease production.

Waterlogging- rising salty groundwater reaches plant roots and inhibits growth

When irrigation is used to make the desert produce crops anotherphenomenon occurs: salinization. Irrigation water always has salts in it. Though normally low in concentration, these salts build up as the water is placed on the land and evaporates. Eventually salts build up to the point where crops will no longer grow. One solution is to flood the land with lots of water, washing the salts deeper into the soil. But eventually this will waterlog the plants. So the land must be drained. Often underground drains are installed which carry the salts away. Usually this means into the river, which was the source of water in the first place. This makes the river saltier and saltier as it picks up more and more drainage. The lower Colorado and Rio Grande rivers are bothextremely saline as a result. A desalinization plant was built in Yuma, Arizona to remove salt from the Colorado before it enters Mexico to meet our treaty obligations.


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Agricultural Practice Problems Solutions and ResultsTilling the soil Erosion when

done on vulnerable land

No-till methods - require use of herbicides and reduce soil processes. Terracing, windbreaks, cover crops, mulching.

Artificial fertilization Salt buildup and soil depletion.

Organic methods: compost, fallowing, crop rotation and cover crops.

Irrigation of dry lands

Salinization and depletion of soil and water resource.

Salt-tolerant crops, desalinization.

Drip irrigation Permaculture, water harvesting, mulching, etc.

Agricultural Practices and Problems


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Aquifers - recharge vs. drawdown, pollution

Video clip on the Ogalala Aquifer

Reservoirs flooding, pollution, competing values

Video clip on western water issues.

Rivers biological changes, pollution, overuse

Video clip on the Rio Grande

Impact Of, and On, Water Resources

One of the most significant effects of agriculture and other land uses is the impact on water resources. You have had the opportunity to examine man's impact on these resources in the [Hydrology] module.

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Text1: Double click on the paper clip icon for each area to learn more.Text2: Click on video icon for video clip on Desertification.Text3: Old Growth Forest Video Clip Text4: The Soil - Video Clip Text5: There is no audio file for this slide. Text6: There is no audio file for this slide.

Terrestrial Biomes - Class Videosclassvideos.net/111/unit_3/biomes-pdf.pdf · What is a Biome? A biome is a basic ... such as the freshwater, marine, and estuarine biomes. Unfortunately,

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