Download Forests and Grasslands

Forests and Grasslands
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Forests—enough precipitation to support stands of trees
Tropical, temperate and polar (boreal)
Tropical Forests
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Heavy rainfall most days
Diversity of life forms
Occupy variety of specialized niches in distinct layers
Near equator
Dominated by broadleaf evergreens
Tree tops form dense canopy
Tropical Forests
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Vines –climb to reach sunlight
Epiphytes—grow on trunks, absorb nutrients
Forest floor—plants with huge leaves capture sunlight
Animal life---insect, bats, birds—most live in canopy
Tropical Forests
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Specialized plants and animal niches—enables coexistence
2% of terrestrial surface area
50% of terrestrial species
Temperate Deciduous Forests
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Survive winter by dropping leaves
Leaves decay and leave rich soil
Average temperatures vary with season
Long warm summers
Cold, but not severe winters
Abundant precipitation throughout year
Tropical Deciduous
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Fewer tree species than tropical
Light penetration allows great plant diversity on forest
floor
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Thick litter layers
Used to have large predators
Evergreen Coniferous
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Cold climates
Cone-bearing trees that keep needles year-round
Boreals or taigas
Winters—long, dry and extremely cold
Sunlight—6-8 hours/day
Summers—short, mild to warm
Evergreen Coniferous
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Diversity—plant is low—too cold
Soils—acidic, thin, nutrient-poor
Large herbivores, smaller carnivores, birds
Temperate Rain Forests
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Coastal
Huge cone-bearing evergreens
Redwoods, Douglas firs
Forests
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Forests with 10% tree cover occupy 30% land surface
Closed canopy—tree crowns spread over 20%
Open canopy—tree crowns less than 20%, woodland
Forests
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Classified by age and structure
Old growth: uncut or regenerated forest not disturbed for
several hundred years, biodiversity treasures, usually remote
 Second-growth: secondary ecological succession, human
activities or natural disaster
 Tree farm: managed tract, one species, uniform age
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Forest Products
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Industrial timber & roundwood—lumber and lumber
products
U.S., Canada, Russia—largest producers
Japan—largest consumer
Forest Management
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Intensive but sustainable management of 1/5 of the
forests meet demands for wood and fiber
Area=2 x area of India
Forest Products
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Fuel wood—1/2 of wood harvested
1.5 billion rely on fuel wood
Open fires<10% efficiency
Metal stoves: 20% efficient
Ceramic stoves: 40% efficient
Non-timber products
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Food
Wildlife habitat
Recreation
Oxygen
Carbon sinks
Reduce erosion
Forest Management
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Even-aged management—same age and size,
economically desirable
Harvested every 6-10 years
Forest Management
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Uneven-aged management—variety of species, many ages
and sizes
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Harvested as ready
Goal—sustainability, biodiversity, quality lumber
Harvesting Trees
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Build logging roads—access lumber and remove
Increase erosion, introduce new species, increase other
uses
Logging road precludes wilderness designation
Harvesting—
Harvesting Trees
Selective cutting of intermediate-or mature-aged trees
 Shelterwood—remove all mature trees in 2-3 cuttings over time
period
 Seed-tree—harvest nearly all trees, except for few uniformly
distributed seed-producing trees
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Harvesting Trees
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Clearcutting—remove all trees from area in single cutting
Strip cutting—harvest strips of trees, leave room for
regeneration
Deforestation
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Temporary or permanent removal of large area of forest
for agriculture or other uses
Decreased soil fertility
Soil erosion
Extinction of species with specialized niches
Deforestation
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Habitat loss for migratory species (birds and butterflies)
Regional climate change
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Releases CO2 into atmosphere from burning and tree
decay
Accelerates flooding
Swidden agriculture
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Slash and burn—clear area for farming and grazing
Can be sustainable, based on rotation and crops
Can cause permanent degradation
Fire Management
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Surface fires—burn undergrowth and leaf litter
Remove flammable materials, stimulate germination, etc
Crown fires—start on ground, move op tree, jump from
tree to tree
Devastating, kill wildlife, erosion increases
U. S. Forest Service
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Part of Dept. of Agriculture
Provide timber
Maintain roads into area, clean debris, rivers
Subsidize logging companies
Sell rights to harvest, less than cost to maintain area &
roads
U. S. Forest Service
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Mixed uses—logging, recreation, grazing, wilderness
Cross purposes
Change of administrations
Bush—salvage logging (what is salvage?)
No new studies for id of wilderness
Thinning
Decrease environmental review and comment period
Tropical Rainforest
Deforestation
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Population growth
Poverty
Government subsidies
Foreign debt
No value to assess ecological value/benefits
Debt-for-nature
Tropical Rainforest
Steeply discount debt--OK
 Decrease sovereignty, change political administrations, etc.
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Grasslands
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Intensely used and altered
Rainfall enough to support grasses, but not forests
27% of land surface
Temperate Grasslands
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Cold winters, hot, dry summers
Deep, fertile soil
Plains, rolling hills in interiors of
North and South America
 Europe
 Asia
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Grasslands
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Pasture—enclosed or managed grasslands
Rangelands—unfenced, natural prairie and open
woodlands
Should be sustainable
Overgrazed
Overfarmed
Grazing
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Conditions of range—rainfall, plant conditions, cover,
nutritional value
Dictate number of animals grazed
Rotational grazing
60% of rangeland –privately owned
26%--BLM (Interior Dept.)
15%--Forest Service
Grazing
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BLM—resource utilization
Cheap rent
Grazing animals exceed carrying capacity
Overgrazed
Unpalatable plants
 Competing herbivores
 Erosion
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Grazing
U. S. fees vs. private fees
Encourages grazing where it shouldn’t be
Overgrazing
Studies have shown that some grassland soils and plants
are harmed by large hooved animals
Who Owns the Land?
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Landowners vs. landless
Rural landless and urban slum dwellers—most poor
individuals
Human dignity, social justice, environmental misuse
Land Reform
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Redistribute land from the few
Mixed success
Indigenous people
Guardians
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How compensated