Forest Ecology

Chapter 12

ForestsTemperate: 75-150 cm even precip throughout year, temperatures -30 to 30 C, oak, hickory, beech, hemlock, maple, elm are plants; animals: squirrels, rabbits, birds, deer, bobcats, foxes Tropical: >200 cm/yr precip even throughout year, 20-25 C, plants: trees like mahogany, orchids, bromeliads, vines, palms, buttressed trunks shallow roots; animals: birds, bats, sm. Mammals, insects Taiga: 40-100 cm precip mostly as snow, very cold temperatures, plants: Evergreen conifers, pine, fir, and spruce, animals: woodpeckers, hawks, moose, bear, weasel, lynx, fox wolf, hares, shrews

FORCING FUNCTIONSFactor that determines the structure/function of an ecosystemHydrology: water topographylight fireNutrient cycling or availability

Range of toleranceeach pop has range of tolerance in physical and chem envindividuals may have slight differences range is usually average conditionsgenetics, age, healthtotal range and optimum range

law of tolerance

The existence, abundance, and distribution of species in an ecosystem are determined by whether the levels or one or more physical or chemical factors fall within the range tolerated by that species. Shelford’s law-presence and success of an organism depend upon the extent to which a complex of conditions are satisfied-excess or too little of these conditions are the limits of tolerance

limiting factor principletoo much or too little of any abiotic factor can limit or prevent growth of a population, even if all other factors are at or near the optimum range of tolerance. 1) hydrology 2)soil 3)nutrients 4)sunlight 5) temperature 6) dissolved oxygen in aquatic systems 7) salinity

Natural resources are vital to us

We need resourcesSoils: agriculture, natural communitiesWater: drinking, agriculture, wildlifeWildlife and fisheries: game, nongame, and marine speciesRangeland: livestockMinerals: mined nonrenewable resources

Maximum sustainable yield

Maximum sustainable yield = aims to achieve the maximum amount of resource extraction

Without depleting the resource from one harvest to the next Populations grow most rapidly at an intermediate size

Population size is about half its carrying capacityManaged populations are well below what they would naturally be

Reducing populations so drastically affects other species and can change the entire ecosystem

Ecosystem-based managementEcosystem-based management = managing the harvesting of resources to minimize impact on the ecosystems and ecological processes

Carefully managing ecologically important areasConsidering patterns at the landscape level Protecting some forested areas

It is challenging for managers to determine how to implement this type of management

Ecosystems are complex, and our understanding of how they operate is limited

Adaptive management evolves and improves

Adaptive management = systematically testing different management approaches and aiming to improve methods

Monitoring results and adjusting methods as needed A fusion of science and managementTime-consuming and complicated

The 1994 Northwest Forest Plan resolved disputes between loggers and preservationists over the remaining old-growth temperate rainforests in the continental U.S.

Allowed limited logging Protected species and ecosystems Science-guided management in Oregon, Washington, and California

Forest ManagementForests cover over 30% of Earth’s land surface

Provide habitat, maintain soil, air, and water quality, and play key roles in biogeochemical cycles Provide wood for fuel, construction, paper production

Foresters, professionals who manage forests through the practice of forestry, must balance ecosystem services with demand for wood products

Ecological value of forestsOne of the richest ecosystems for biodiversity

Structural complexity houses great biodiversityA forest provides many ecosystem services

Stabilizes soil and prevents erosionSlows runoff, lessens flooding, purifies waterStores carbon, releases oxygen, moderates climate

Economic value of forestsBenefits: fuel, shelter, transportation (boats), paper Helped society achieve a high standard of livingLogging Locations:

Boreal Forests: Canada, RussiaRainforests: Brazil, IndonesiaConifer Forests/Pine Plantations: U.S.

In 2005, over 1/3 all forests were designated for timber production

Demand for wood leads to deforestationDeforestation = the clearing and loss of forests

Alters landscapes and ecosystemsDegrades soilCauses species decline and extinctionRuins civilizationsAdds carbon dioxide to the air

Developing countries boost their economies and get land for their growing populations by logging forests

Deforestation in America and CanadaDeforestation propelled the westward expansion and growth of America and Canada

Eastern deciduous forests were the first to be logged for farms and to build cities (i.e., Chicago)Timber companies moved south to the Ozarks and west to the Rockies

Loggers moved westward, searching for large trees

Primary forest = natural forest uncut by people Little remained by the 20th century

Second-growth trees = grown to partial maturity after old-growth timber has been cut

Loggers lose their jobs with deforestation

As each region is deforested, the timber industry declines and moves on

Local loggers lose their jobs

Once the remaining ancient trees of North America are gone, loggers will once again lose jobs

Companies will simply move to another area

The scarcity of remaining old-growth trees fuels scientific concerns and empassions environmentalists

Deforestation is proceeding rapidly worldwide

Uncut tropical forests still remain in many developing countriesTechnology allows for even faster exploitationDeforestation is rapid in places such as Brazil and Indonesia

Developing countries are so desperate for economic development, they have few logging restrictions

Short-term economic benefits go to foreign multinational corporationsGovernments often help companies, at the expense of native people

“Timber famine” fears spurred forest protection

National forest system = a system of forest reserves and public landsTo grow trees, produce timber, protect watersheds, and ensure future timber suppliesResulted from depletion of U.S. forests and fear of a “timber famine”77 million ha (191 million acres); 8% of the U.S. land area

The U.S. Forest Service was established in 1905 Manage forests for the greatest good of the greatest number in the

long run, including logging

Federal agencies own land in the U.S.

Timber is extracted from public and private land

Timber is extracted by private companies, even on public landForest Service employees plan and manage timber sales and build roadsThe companies log and sell the timber for profit

Most logging occurs on private landBut, millions of cubic feet per year are still logged from national forests

Timber harvesting remains stable in developed countriesTimber companies manage forests according to the maximum sustained yield approach

Management on public lands reflects economic forces, along with social and political ones

These change over timePublic concern, changing management philosophies and economics caused harvests to decrease

Plantation forestryThe timber industry focuses on timber plantations

Fast-growing species MonoculturesEven-aged trees = all trees are the same age

Trees are cut at the end of the rotation time and replantedPlantations are crops, not functional forests

Some harvesting methods maintain uneven-aged (mixed ages of trees and species) tree stands

Harvesting timber: clear-cuttingAll trees in the area are cutMost cost-efficientGreatest impact on forest ecosystemsMay mimic some natural forms of disturbanceDestroy entire communitiesSoil erosionPublic is outraged over this type of harvesting

Harvesting: other methodsSeed-tree cutting = a small number of seed-producing trees are left standing to reseed the area Shelterwood cutting = a small number of trees are left to provide shelter for the seedlings Selection systems = only select trees are cut

Single tree selection = widely spaced trees are cutGroup tree selection = small patches of trees are cut

All methods disturb habitatChange forest structure and compositionIncrease erosion, siltation, runoff, flooding, landslides

Public forests can be managed for many things

Increased public awareness caused people to urge changed forest management

For recreation, wildlife and ecosystem integrity, instead of loggingCritics protested federal subsidies of logging companies

Multiple use policy = national forests were to be managed for recreation, habitat, minerals and other uses

In reality, timber production is the primary use

The Forest Service loses $100 million/yr by selling timber below cost

Harvesting forests

The National Forest Management Act (1976)

Mandated that plans for renewable resource management had to be drawn up for every national forestGuidelines included:

Consideration of both economic and environmental factorsProvision for species diversityEnsuring research and monitoringPermitting only sustainable harvestsProtection of soils and wetlandsAssessing all impacts before logging to protect resources

New forestry management is under attack

Calls for timber cuts that mimic natural disturbancesHarvesting methods are based on ecosystem approaches

The Bush administration has rolled back these regulationsFreed managers from requirements of the ActLoosened environmental protectionsRepealed President Clinton’s roadless rule, which protected 31% of national forests from road buildingCalifornia, Oregon, and New Mexico have sued the government to reinstate the roadless rule

Fire policy also stirs controversyFor over 100 years, the Forest Service suppressed all fires

But many ecosystems depend on firesFire suppression allows woody accumulation, which produces kindling for future fires

Which are much worseHousing development near forests and climate change will increase fire risk

Prescribed fires are misunderstood

Prescribed (controlled) burns = burning areas of forests under carefully controlled conditions

EffectiveMay get out of controlImpeded by public misunderstanding and political interference

Healthy Forests Restoration Act (2003) = promotes removal of small trees, underbrush and dead trees

Passed in response to forest fires

Salvage loggingRemoval of dead trees following a natural disturbanceSeems logical, but is really destructive

Snags (standing dead trees) provide nesting cavities for countless animalsRemoving timber from recently burned areas increases erosion and soil damagePromotes future firesIncreases commercial logging in national forestsDecreases oversight and public participation

Sustainable forestry is gaining groundSustainable forestry certification = only products produced sustainably can be certified

International Organization for Standardization (ISO), Forest Stewardship Council (FSC) have different standardsConsumers look for logos to buy sustainably produced timberCompanies such as Home Depot sell sustainable wood

Encourages better logging practices

Agricultural land use

Agriculture covers 38% of the Earths’ terrestrial surface26% supports pasture, 12% supports cropsThe most widespread type of land useCauses tremendous environmental impacts

Governments spend billions of dollars on subsidiesProponents say farmers need this insurance against bad yearsCritics say farmers should buy their own insurance

Wetlands have been drained for farming

Many crop lands grow on former wetlandsGovernments have encouraged wetland draining

Promote settlement and farmingTransferred land to statesStimulated draining

Less than half the wetlands remain

Perspectives on wetlands are changing

Many people have a new view of wetlandsNot worthless swamps, but valuable ecosystemsDemanded regulations to safeguard remaining wetlandsBut, because of loopholes, wetlands are still being lost

Conservation Reserve Program (1985) subsidized farmers to take highly erodable land out of production

Turn it into wildlife habitat

Livestock graze one-fourth of Earth’s landGrazing can be sustainable if done carefully and at low intensityBureau of Land Management (BLM) = owns and manages most U.S. rangeland

Nation’s single largest landowner: 106 million ha (261 million acres) across 12 western statesRanchers can graze cattle on BLM lands for low feesLow fees encourage overgrazing

Ranchers and environmentalists have joined to preserve ranchland against development and urban sprawl

Management of the American West

Overexploitation of resources caused great damage to the American West

Poor farming practices, overgrazing, farming arid lands

John Wesley Powell in the late 1800s called for agencies to base management on science

Farming Western lands had to account for arid conditionsHis ideas were ignored, contributing to failures such as the Dust Bowl of the 1930s

Parks and reserves

Reasons for establishing parks and reserves include:Monumentalism = preserving areas with enormous, beautiful or unusual features, such as the Grand CanyonOffer recreational value to tourists, hikers, fishers, hunters and othersProtect areas with utilitarian benefits, such as clean drinking waterUse sites that are otherwise economically not valuable and are therefore easy to protectPreservation of biodiversity

Federal parks and reserves began in the U.S.National parks = public lands protected from resource extraction and development

Open to nature appreciation and recreationYellowstone National Park was established in 1872

The Antiquities Act of 1906 The president can declare selected public lands as national monuments

The National Park Service (NPS)

Created in 1916 to administer parks and monuments388 sites totaling 32 million ha (72 million acres)Includes national historic sites, national recreation areas, national wild and scenic rivers273 million visitors in 2006

National Wildlife RefugesBegun in 1903 by President Theodore Roosevelt37 million ha (91 million acres) in 541 sitesU.S. Fish and Wildlife Service administers refuges

Management ranges from preservation to manipulationWildlife havensAllows hunting, fishing, wildlife observation, photography, education

Wilderness areasWilderness areas = area is off-limits to development of any kind

Open to the public for hiking, nature study, etc.Must have minimal impact on the landNecessary to ensure that humans don’t occupy and modify all natural areas

Established within federal landsOverseen by the agencies that administer those areas

Not everyone supports land set-asidesRestriction of activities in wilderness areas generated opposition to U.S. land protection policies

Some western states want resource extraction and development

The wise-use movement = a coalition of individuals and industries that oppose environmental protection

Protecting private property, transferring federal lands to state or private hands, promoting motorized recreation on public landsFarmers, ranchers, loggers, mineral and fossil fuel industries

Wilderness protection has been weakened

President George W. Bush has weakened wilderness protection

Federal agencies have shifted policies and enforcementAway from preservation and conservation Toward recreation and resource extraction

Nonfederal entities also protect landEach U.S. state and Canadian province has agencies that manage resources

So do counties and municipalities

Land trusts = local or regional organizations that purchase land to protect it

The Nature Conservancy is the world’s largest land trustTrusts protect 4.1 million ha (10.2 million acres)Jackson Hole, Wyoming is protected by a land trust

Parks and reserves are increasing internationally

Many nations have established national parksBenefit from ecotourismProtected areas now cover 9.6% of the world’s land area

Parks do not always receive necessary fundingPaper parks = Areas protected on paper but not in realityWorld heritage sites = protected areas that fall under national sovereignty but are designated or managed by the United Nations

830 sites across 184 countries

Transboundary and peace parksTransboundary park = an area of protected land overlapping national borders

For example, Waterton-Glacier National Parks in the U.S. and Canada

Peace parks = transboundary reserves that help ease tensions by acting as buffers between nationsBiosphere reserves = land with exceptional biodiversity

Couple preservation with sustainable development

Biosphere reserves have several zones

This can be a win-win situation for everyone

Habitat fragmentation threatens speciesContiguous habitat is chopped into small pieces

Species suffer

The SLOSS dilemmaWhich is better to protect species?

A Single Large Or Several Small reserves?Depends on the species: tigers vs. insects

Corridors = protected land that allows animals to travel between islands of protected habitat

Animals get more resourcesEnables gene flow between populations