March 27, 2014: Introduction to climate.
If you have not yet taken Exam 1 or Exam 2,
please email me to set up a time to take a
makeup. All makeup exams should be completed
before taking Exam 3.
Climate: long term average weather
30 year average in U.S.
precipitation
temperature
seasonal variations in monthly averages
wind speed and direction
cloud cover
Use climograph to display climate data
Climograph
Average Annual Precipitation = 60”
graph that shows
monthly average
temperature and
precipitation for a
given place
Climate regions cover large areas
Within these large regions are MICROCLIMATES
Boundaries between climate types are not sharp
lines like on a map.
local anomaly in overall climate pattern.
Ecotone: transition zone between one ecosystem
and another along some kind of environmental
gradient (temperature, moisture, etc.)
An oasis in
desert is one
example of a
microclimate
Ecosystem: biological community and its physical
environment.
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Example of ecotone
Köppen Climate Classification System
Six Major Climate Types:
Arid vs. humid  “B” climates = arid
Humid climates subdivided by temperature:
Wet
Moisture gradient
warmest…………coldest
“A”… “C”… “D”… “E”
Dry
Distribution of tree species in Santa Catalina Mountains,
Arizona. Note that species replace each other gradually
(Whittaker, 1967)
Altitude  “H”
Subdivisions of major types based on seasonality of
precipitation.
KOPPEN MAJOR CLIMATE TYPES
General location of major climate types
E: too cold for trees
Treeline
D: long winter
H
C: long summer
B: arid
Freezeline
A: never freezes
Name
Parameters
Vegetation
B: Arid
P<PET
Xerophytes/annuals
A: Tropical
Never freezes
C: Mesothermal
Mild mid-lat.
Long summer
Broadleaf evergreens
in wet places
Broadleaf deciduous
D: Microthermal Long winter
Severe mid-lat.
Needleleaf evergreens
E: Polar
Too cold for trees Shrubs & herbs
in warmer parts
H: Highland
Up in altitude =
up in latitude
Alpine
Biomes:
Plant formations associated with major climate types.
Relationship between plant form and and climate
based on needs for plant photosynthesis
How plants make a living : PHOTOSYNTHESIS
Tropical rainforest
Tropical savanna
Desert
Temperate grassland
Temperate forest
Mediterranean scrub
Boreal forest
Tundra
Ice
carbon dioxide + water + sunlight  glucose + oxygen
6 CO2 + 6 H20 + energy  C6H12O6 + 6 O2
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Things plants must have to survive for long:
Plant form = overall shape, lifestyle, shedding habit, leaf
design.
carbon dioxide
Individual plant form allows plants to take advantage of
water
water
light
light
some nutrients/minerals
temperature
some warmth
nutrient/mineral levels
Calcium, Magnesium, Iron, Zinc
These resources vary spatially with climate and soil,
except for ____________________?
Form helps plant to acquire/conserve necessary
ingredients and to optimize photosynthesis and growth.
Transpiration
Leaf shape:
Plants lose
water through
their leaves
Plants take in
water through
their roots
Broad leaves
Stomates allow CO2 in, O2 and H2O out
LEAF SHAPE
Leaf shape:
Needle leaves
Broadleaf
Needleleaf
Surface
Area/pho.
rate
Water
Loss
Foliage
Cost
Water/
Nutrient
Needs
High
High
High
High
Low
Low
Low
Low
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Shedding habits also differ
SHEDDING HABIT
Loses
Leaves
All once
a year,
may go
dormant
Deciduous
Evergreen
Broadleaf evergreen
Broadleaf deciduous
High water/nutrient/
warmth needs all year
High water/nutrient/
warmth needs during
growing season only
High photosynthetic rate
High growth rate
Lower overall growth rate
than Broadleaf evergreen
TROPICAL RAINFOREST
LONG SUMMER CLIMATES
Needleleaf evergreen
Needleleaf deciduous
Low water/nutrient/
warmth needs all year
Low water/nutrient/
warmth needs during
growing season only
Low photosynthetic rate
Low growth rate
SHORT SUMMER CLIMATE
Needle leaves
Water
Needs
Only
when
tree has
leaves
Loses some
All year
during the
year, never
dormant
Payment
Plan
Length of
Growing
Season
Cash up
front
Long
enough to
“save up”
for new
leaves
Installment
plan
All year
Broad leaves
and
evergreen
in Mobile
Magnolia has
stiff almost
“woody
leaves”
Lowest overall growth rate
HIGH STRESS CLIMATES
OR SITUATIONS
Live oak is techically “deciduous” because it loses all of its
leaves at one time and has to replace them all each year.
and
deciduous
in Mobile
Baldcypress
lives in high
stress
conditions of
swamps
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Within “B” (arid) major climate, two subtypes
Arid “B” climates: P<PET
precipitation < potential evapotranspiration
moisture is the determining factor
rainfall low AND unreliable
BW: Desert
P < ½ PET
plants
mainly lack of mechanism to “lift” air
drought evaders = annuals
some “B” climates freeze, some do not
drought resistors = perennials
most extensive climate type
BS: Steppe
PET > P > ½ PET
short grasses
high risk of desertification
BW Climate
BS Climate
Characteristics of “B”
low relative humidity
no clouds ... high atmospheric transparency
high diurnal (daily) temperature range
precipitation low and unreliable
erosion and flash flooding severe
dew and fog important moisture sources (Chile)
strong winds due to unequal heating
dunes present only if adequate sand supply
desert pavement common
Hypothetical continent
What is where and why?
60°
Four Major Causes of Arid Climates
1. Location near subtropical high pressure belt
30°N or 30°S
30°
2. Location in continental interior
0°
3. Location behind mountain barriers
4. Location near cold ocean currents
30°
60°
No “B” climates at
high latitudes. Why?
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Location of “B” climates
North American Deserts
Causes of B climates
STH
Interior
Mt. barriers
30°
Cold currents
Great basin
Mojave
Sonoran
STH, Interior, Mt. barriers, Cold currents
Chihuahuan
Desert plants cope with water deficiency in two ways
1. Drought evaders: annual plants that have a short
life after it rains. Spend most time as dormant
seeds.
Drought evaders
Drought resistors
Annuals
Perennial xerophytes
2. Drought resistors: perennial plants that tough it out
and have adaptations that enable them to live with
very little water. These are called xerophytic plants.
Characteristic spacing of xerophytes (ocotillo)
Characteristics of xerophytes
Foliage…most can be shed during drought
sparse
small needle shaped leaves
waxy coatings
hairs
or...no leaves just green stems, succulents
Photosynthesis – CAM pathway common
stomates open at night to take in CO2
close in day to reduce water loss
photosynthesis uses daylight and CO2
stored the night before
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North
American
Cactaceae
African
Euphorbiaceae
Characteristics of xerophytes, contd.
Roots
deep rooted (160’ mesquite)
and/or widespread shallow roots
Growth habit
relatively short
succulent
spiny or toxic
Example of
convergent
evolution
Sonoran Desert has more rain and more vegetation
Kangaroo rat
Namib Desert
How they do it....
Desert animals
Body temperature range 98-108
Most nocturnal
Blood volume kept high at expense of tissue fluid
Get water from food
Most are small
Can safely lose 40% of body water weight
Urine thick, feces dry
Lizard
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Short grass prairie associated with BS climate
BS or Steppe climates
Spring greening
transition between tall-grass prairies and true desert
vegetation
short grasses
bunch grasses
good pasture
overgrazed easily
vulnerable to desertification
Desertification of arid and semi-arid lands
Process whereby productive potential of arid or semi-arid
land falls by 10% or more, primarily due to human activities.
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