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Transcript
Tropical Biomes of the World
ƒ Tropical Evergreen
Forests (rain forests)
ƒ Tropical Deciduous
Forests (seasonal
forests or monsoon
forests)
ƒ Tropical Scrub
“Forests”
Forests”
ƒ Tropical Grasslands
Tropical Biomes in North America
Tropical Rain Forests
ƒ Cover 6% of
world land area
ƒ Contain 7575-90%
of the world’
world’s
plant and animal
species
Tropical Rain Forests: Climate
ƒ Hot and wet
ƒ Average annual
precipitation
– 100100-180”
180”
– (60(60-400”
400” range)
ƒ Distributed evenly with
short droughts
ƒ Temperatures uniform
– Warm to hot (80(80-90 F)
– Daily fluctuation often
as large as annual
Tropical Rain Forests:
Dominant Life Form
ƒ Broadleaved evergreen trees dominate
ƒ Drop and replace leaves individually rather
than collectively
ƒ Often flower and fruit in different seasons
Tropical Rain Forests: Diversity
ƒ Extremely high diversity—
diversity—both plants and animals
ƒ Costa Rica has over 200 families that contain trees
ƒ One Brazilian rain forest contains 300 tree species in a
single square mile
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Tropical Rain Forest: Layers or Strata
Tropical Rain Forest: Layers
ƒ Emergent
layer
ƒ Intermediate
layer
ƒ Understory
layer
Tropical Rain Forests: Emergent Layer
Trees 7575-150’
150’ tall
Long, unbranched trunks
Fluted and buttresses bases
Tropical Rain Forest: Intermediate Layer
ƒ Trees 1515-75’
75’ tall (typically not
fluted or buttressed)
ƒ Dense canopy
ƒ Low light and high humidity
(within & below)
Unusual Strategies:
Unusual Rooting Strategies:
Prop roots, strangler figs, twisting vines
Pneumataphores,
Pneumataphores, Aerial Roots & Prop Roots
2
Tropical Rain Forests: Epiphytes
Tropical Rain Forest:
Vines and Lianas
Twisting, snarling, suffocating
Some germinate in the ground and some in the canopy
Tremendous growth rates
Link tree canopies together
Often need to be cut before falling trees
Importance of vines
Tropical Rain Forests: Understories
ƒ Vary dramatically
– depends on light and
disturbance
ƒ Heavy overstory means less light
and less understory
ƒ Disturbed overstory means dense
understory
Tropical Rain Forests: Understories
ƒ Open canopies (typically
disturbed) result in
dense understories
(jungle(jungle-like)
Tropical Rain Forests: Productivity
High net productivity—
productivity—high respiration
3
Tropical Rain Forest: Soils
Competing uses for tropical forest land
Diverse and highly variable
Many soils low in nutrients
High losses to runrun-off and leaching
Most nutrients held in plants
Adverse effects from removing vegetation
Tropical Rain Forests:
Deforestation
Shifting Agriculture
(Slash and Burn)
ƒ Estimate: 80 acres harvested every minute
ƒ Once occupied 16% of world’
world’s surface—
surface—now about 6%
ƒ Impact: loss of species diversity, loss of carbon sequestration,
uprooting of indigenous peoples, loss of medicines (25% of
medicines derived from rain forest plants)
Mangrove “Forests”
Forests”
ƒ
ƒ
ƒ
ƒ
ƒ
Occur throughout tropical regions where forests meet the ocean
Multiple genera—
genera—2525-30 species
Always associated with salt water
Different species tolerate different amount of salt
Not all mangroves have same adaptations
Mangrove Adaptations:
Pneumataphores
4
Mangrove Adaptations:
Viviparous Seedlings
Mangrove Adaptations:
Prop Roots
Mangroves on the march
Tropical Rain Forests: Biodiversity
Tropical Rain Forests:
Biodiversity
Tropical Rain Forest: Animals
ForestForest-dwelling kingfisher
Cauliforous flowering and fruiting
Forest termites
Chameleon
5
Trends and Issues
Tropical Deciduous Forests
ƒ Deforestation
– once 16% land’
land’s area, now
6%
ƒ Animal harvest
–
–
–
Survival food
Pet trade
Souvenirs and aphrodisiacs
ƒ Contribution to
atmosphere
– water, oxygen, and carbon
sequestration
ƒ Medicinal values
– perhaps 25% world’
world’s
medicines come from here
ƒ Loss of biological diversity
Tropical Deciduous Forests
ƒ High rainfall—
rainfall—up to
8oo”
8oo”/year!
ƒ Seasonal distribution
– Very wet and bone dry
ƒ Temperatures tend to be hot
– cold periods in northern
regions and higher elev.
ƒ Vegetation has less
diversity than tropical rain
forests but more than other
regions
Tropical Deciduous Forests
ƒ Trees commonly drydryseason deciduous
– Lose leaves at same time
ƒ Commonly transition
into savannah lands or
desert grasslands on dry
end—
end—tropical rain
forests on wet end
ƒ High tree diversity
– 4040-100 spp./hectare
– < tropical rain forests but >
temperate forests
Important Trees
ƒ No single species
dominates
ƒ Teak and
mahoganies are
most important
commercial
species
ƒ Teak native to
southeast Asia, but
widely planted
Bamboo
ƒ Grass rather
than woody
ƒ Many species
ƒ Commonly
lowland, wet
site plant
ƒ Astronomical
growth rates
ƒ Very important
for building
6
Epiphytic Cacti
Cultural Significance
Trends and Issues
Animals
ƒ LargeLarge-scale
agriculture
ƒ Social pressure
– Population
– Poverty
ƒ Grazing
ƒ Harvest for
firewood
Tropical Grasslands and ThornThorn-Scrub
(Savannas)
Tropical Grasslands
ƒ Climate hot and dry. Rains seasonal.
ƒ Grasses dominant life form. Scattered clumps of trees exist
7
ThornThorn-scrub “forests”
forests”
ƒ
ƒ
ƒ
ƒ
Browse lines in acacias
Trees small and drought resistant
Many have deep tap roots
Most heavily armed with spines and thorns
Although that doesn’
doesn’t stop browsing
Primary use of wood: Fuel
Vast herds of migratory grazers
Domestic livestock
Home of big cats
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..and plaques of grasshoppers
and locusts
9