Transcript Ecology (BIO C322)

Ecology (BIO C322)
Terrestrial Biomes
Major World Biomes
Whittaker’s Patterns of World Formations
Dominant Plant Life Forms of
Terrestrial Ecosystems
• Trees: Woody tissue advantageous for
height & access to light, but cost of
maintenance & respiration.
• Shrubs: Allocate lower % of resources to
supportive tissues (stems).
• Grasses: Least amount of carbon
allocated for production of stems.
Conditions restricting Photosynthesis
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Dryness;
Low nutrient concentrations;
Short growing season;
Cold temperatures.
Polar Ice Caps
Ice Algae
Polar & High-mountain Ice caps
• Extreme environments but not lifeless.
• Microbial life: Ice algae (photosynthetic
diatoms) under ice  Psychrophiles/
Extremophiles.
• Lakes under Antarctic ice caps contain
microorganisms  colour the ice brown (high
conc of photosynthetic pigments).
• Other adaptations: Membrane fatty acids??
• “Aeolian biomes” (aeolus = wind).
• Winds blowing from below (bringing in detritus).
Alaskan Tundra
Reindeer Moss
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Tundra (60o N Lat)
Lies b/w forests (south) to polar
ice caps (north).
Low temp, short growing seasons.
Low rainfall but not limiting.
Permafrost: Permanently frozen deep soil;
upper portion may melt in summer.
Vegetation: Grasses, sedges, dwarf woody
plants, lichens (reindeer moss  Cladonia
rangiferina);
No trees.
• Spongy mat of living & slowly decaying
vegetation.
• Migratory birds & insects abundant
 not enough productivity in one area.
• Musk ox, reindeer, polar bears, wolves,
foxes.
- Arctic Tundra: In extreme northern
latitudes.
- Alpine Tundra: On mountain tops.
Leaf Form & Ecosystem Classification
• Deciduous: Live for only a single year/
growing season; leaves shed at end.
• Advantage: No extra cost of maintenance &
respiration during the period when env
conditions restrict photosynthesis.
– Winter-deciduous leaves
– Drought-deciduous leaves
Banyan (Ficus benghalensis) – Deciduous tree
Peepal (Ficus religiosa) – Deciduous tree
• Evergreen leaves: Live beyond a year.
– Broadleaf-evergreen: Photosynthesis &
growth continue year round (Tropical rain
forests).
– Needleleaf-evergreen: Short growing season
(northern latitudes), nutrient availability
constrains photosynthesis (conifers).
Needle Leaf
Additional Features
• Needle-shaped leaves of conifer trees:
Strong, Less no. of stomata, less water loss, low
frost damage; fix carbon all year; more defensive
compounds and structure help prevent herbivore
damage (Long life  More chance of damage).
• Broad leaves of deciduous trees: Shed leaves
during dry season (becoming dormant) to
preserve water; rely on reserves to support
respiration; drought avoiders.
Practice Concept – A Model for Leaf Adaptation
• The production of a leaf has a “cost” to the plant = the
carbon & other nutrients required to construct the leaf.
• The time required to pay back the cost of production
(carbon) is a function of the rate of net photosynthesis.
• If rate of photosynthesis is low, it may not be possible to
pay back the cost over period of a single growing season.
• A plant adapted to such conditions can’t afford deciduous
leaf form, which requires producing new leaves every year.
• The needle-leaf evergreens, however, can pay back the
cost of leaf production as they survive for a no. of years.
Northern Coniferous Forest Biomes 45th
and 57th North latitudes
• Evergreen forests stretching across N.
America & Eurasia.
• Also called Taiga or Northern Circumpolar
Boreal Forest.
• Identifying life forms: Coniferous, needleleaved tree species like spruce (Picea sp.),
fir (Abies sp.) & pine (Pinus sp.).
• Source of lumber/timber.
Coniferous Deodar Forest
(Cedrus deodara)
Temperate Deciduous Forests
• Occupy areas with abundant rainfall (75-150
cm) & moderate temperatures.
• Europe, N. America, Japan, Australia, S. Am.
• Trees & shrubs without leaves for part of year.
• Herb & shrub layers well-developed.
• Trees: Beech, maple, oak, poplar.
• Animals are deer, bear, fox squirrels,
foxes, woodpeckers, etc.
Beech-Maple Forest
Oak-Hickory Forest
Temperate Grasslands (Prairies, Pampas)
• In areas of intermediate (b/w forests & deserts) rain
(25-75cm).
• N. & S. America, Eurasia, Australia.
• Tall, midsize & short size grasses  declining rainfall.
• Root biomass >> aboveground parts.
• Forbs (non-grass herbs), like legumes, also present.
• Rich in humus due to short life  Rapid humification,
slow mineralization.
• Fire helps maintain grassland vegetation
in competition with woody vegetation.
• Grazers/herbivores - bison, kangaroos.
Tropical Grasslands & Savannas
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Grasslands with scattered clumps of trees.
In semi-arid regions with intermediate rain.
Fires in dry season.
Africa, S. America, Australia,
mid India.
• Genera of grasses: Andropogon, Panicum.
• Trees: Acacias, palms.
• Hoofed mammals:
antelope, zebra,
giraffe, lions.
Residents of the African Savanna
Chaparrals – Fire type Biomes
Chaparral
Chaparral has a very specific spatial distribution.
It is found in a narrow zone between 32 and 40 degrees latitude
North and South on the west coasts of the continents.
This area has a dry climate because of the dominance of the
subtropical high pressure zone during the fall, summer, and
spring months.
precipitation falls mainly in the winter months
Annual averages range from about 300 to 750 millimeters and
most of this rain falls in a period between 2 to 4 months long.
As a result of the climate, the vegetation that inhabits this biome
exhibits a number of adaptations to withstand drought and fire.
Trees and shrubs living in this zone tend to be small with hard
evergreen leaves.
Plants in the chaparral do not drop their leaves during the dry season because of the
expense of replacement.
The dry climate slows the rate of leave decomposition in the soil. As a result, the
plants growing in this biome do not have nutrients available for uptake to produce
new leaves when the wet season begins.
Instead, the plants of the chaparral develop leaves that can withstand arid
conditions.
Representative species of the chaparral include cork oak (Quercus suber), olive
(Olea europaea), eucalyptus, arbutus (Arbutus unedo), acacia, maritime pine (Pinus
pinaster), shrub oak (Quercus dumosa), and live oak (Quercus virginiana). Many of
the plant species have thorns to protect them from herbivore damage.
This biome is sometimes also called Mediterranean Scrubland or sclerophyll forest.
Deserts
• Regions with < 25 cm annual rainfall.
• Less rain - high pressure/ rain shadow/ high elevation.
• High temp during summer, low during winter  Low
precipitation distinctive characteristic.
• Cold deserts & hot deserts.
• e.g. Sahara (Africa), Thar (North west India).
Adaptations to Water Scarcity
• Plants: Annuals / ephemerals (grow only in adequate
moisture – drought evaders),
• Stem succulents [CAM plants (stomata open at night)
like cactus].
• Desert shrubs  Leaves shed in long dry season,
regularly spaced distribution (with large bare areas)
to avoid competition for nutrients & water (Artemisia).
• Adaptations in animals: Dry excretions (uric acid),
impervious integuments (insects, reptiles), tissues
tolerant of high body temperature (camels).
Body Temperature of the Camel and Its Relation to Water
Economy. Am J Physiol 188: 103-112 (1956)
The variations in temperature (34-40ºC) are of great
significance in water conservation in two ways.
a)The increase in body temperature means that heat is
stored in the body instead of being dissipated by
evaporation of water. At night the excess heat can be
given off without expenditure of water.
b) The high body temperature means that heat gain
from the hot environment is reduced because the
temperature gradient is reduced.
"Unique properties of the camel erythrocyte membrane, II.
Organization of membrane proteins"
Biochim Biophys Acta 426: 647–58 (1976)
It is proposed that protein-protein interaction of
integral proteins, presumably constituting an “integral
skeleton”, is a dominant structural feature stabilizing
the camel erythrocyte membrane.
"Veterinary medicine. 'Camelized' antibodies make waves"
Science 318: 1373-1374 (2007)
In all mammals, the Y-shaped antibody molecules consist
of two heavy (or long) chains along the length of the Y,
and two light (or short) chains at each tip of the Y. Camels
also have antibody molecules that have only two heavy
chains, which makes them smaller and more durable.
Tropical Rain Forests
• Warm climate with high, uniform rain.
• India (Karnataka, Kerala, NE), Africa, S. Amer.
• Highly stratified: Tall, emergent (> 60m),
canopy (25-35m), understory (15-24m), poorly
developed shrubs(shade), ground layer (herbs).
• No prolonged dry season  Evergreen plants.
Epiphytic growth of mosses/ferns on tree trunks,
lianas (climbing vines).
• High biodiversity  crowded ecosystems.
• High rate of evolutionary change / speciation.
• Decomposition fast  no litter accumulates  Rapid
nutrient reabsorption by plants.
• From equator towards tropics/subtropics  Greater
seasonality in rain  Tropical evergreens replaced
by drought-deciduous trees (leaf fall in dry season).
• A cleared tropical forest area - poor cropland.
Role of Ecosystem People in protecting Forests
Chipko Movement
• Hugging trees to protect them from being felled.
• 1730 A.D., Bishnois of Rajasthan sacrificed
their lives to protect sacred khejdi (Prosopis
cineraria) trees.
• 1974, in Garhwal Himalayas of Uttarakhand.