BIOMES

1
BIOMES I. Climatic Determinants II. FORESTS III.
Grasslands
2
III. Grasslands A. Shrub Forest - Savannah
3
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions TEMP Uniformly warm annual
temp gt 20C a bit more seasonality due to warmer
temps during arid dry season RAINFALL seasonal
- closer to tropical margins rainfall determines
tree density, from shrub forest ot tropical
savannah with a few trees to true grassland
EVAPOTRANSPIRATIONAL STRESS high, espcially in
dry season selects for C4 grasses LIGHT Never
limiting, no winter and no big trees creating
shade SOILS low permeability - calcium
carbonate hardpan creates waterlogged surface in
wet DISTURBANCE fire - selects for grasses
NUTRIENTS and CYCLING Most nutrients bound in
biomass rapid decomposition and rapid
absorption. Little litter accumulation.
4
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota
5
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses
6
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses In "C3"
photosynthesis, the process we have already
learned, CO2 is first bound to a C5 molecule -
making an unstable C6 molecule that splits into
two C3 molecules...glucose is produced and the
C5's are recycled...
6(CO2)
6(C6)
6(C5)
C6 (Glucose)
5(C6)
7
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses In "C3"
photosynthesis, the process we have already
learned, CO2 is first bound to a C5 molecule -
making an unstable C6 molecule that splits into
two C3 molecules...glucose is produced and the
C5's are recycled...
6(CO2)
But there is a big problem when things get dry.
The plants close the pores in their leaves to
reduce water loss ('cuz it's dry!), and this
stops gas exchange, too. So no more CO2 gets
into the leaf, and no O2 can get out.
6(C6)
6(C5)
C6 (Glucose)
5(C6)
8
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses In "C3"
photosynthesis, the process we have already
learned, CO2 is first bound to a C5 molecule -
making an unstable C6 molecule that splits into
two C3 molecules...glucose is produced and the
C5's are recycled...
6(CO2)
But there is a big problem when things get dry.
The plants close the pores in their leaves to
reduce water loss ('cuz it's dry!), and this
stops gas exchange, too. So no more CO2 gets
into the leaf, and no O2 can get out. And so, as
photosynthesis proceeds in a closed leaf, CO2
decreases and the O2 increases.
6(C6)
6(C5)
C6 (Glucose)
5(C6)
9
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses In "C3"
photosynthesis, the process we have already
learned, CO2 is first bound to a C5 molecule -
making an unstable C6 molecule that splits into
two C3 molecules...glucose is produced and the
C5's are recycled...
O2
(CO2)
This is bad because the C5 molecule can only bind
CO2 when it's in high concentration. As the
CO2 drops, the C5 molecules bind to oxygen and
are metabolized... and glucose production
STOPS... (this is BAD).
6(C6)
6(C5)
C6 (Glucose)
5(C6)
C5 BREAKDOWN
10
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses In "c4"
photosynthesis, the C3 pathway is isolated in
special cells, in which the CO2 concentration can
be kept high (so that glucose production will
continue).
6(CO2)
6(C6)
6(C5)
C6 (Glucose)
5(C6)
11
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses The CO2
concentration is kept high by "pumping it in"...
PEP is a C3 molecule that binds CO2 even at low
concentrations (making a C4 molecule.
6(CO2)
CO2
6(C6)
C4
PEP (C3)
6(C5)
C6 (Glucose)
5(C6)
12
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses This C4 molecule is
transferred and broken releasing CO2 and
recycling PEP. So CO2 is high in the special
cell and glucose production continues.
6(CO2)
CO2
6(C6)
C4
6(C5)
C6 (Glucose)
PEP (C3)
PEP (C3)
5(C6)
13
III. Grasslands A. Shrub Forest - Savannah 1.
Abiotic Conditions 2. Biota Arid conditions and
fire select for C4 grasses SO, CO2 fixation is
spatially separate from Glucose production.
6(CO2)
CO2
6(C6)
C4
6(C5)
C6 (Glucose)
PEP (C3)
PEP (C3)
5(C6)
14

• III. Grasslands
• A. Shrub Forest - Savannah
• 1. Abiotic Conditions
• 2. Biota
• Arid conditions and fire select for C4 grasses
• Large grazers dominate harvest energy by
  processing huge amounts of forage quickly, or by
  ruminating (bacterial gut flora). Migratory

15
Cows are "foregut fermenters"... food goes
straight to a fermentation sac (rumen) with
bacteria....they regurgitate food and chew it
several times (chewing cud) before it passes to
the intestine for the extraction of nutrients...
16
Horses are "hindgut fermenters"... food goes to
the stomach and then to the intestine, with no
regurgitation. The large intestine a caecum
(blind sac) have bacteria that break down the
cellulose. They must eat pretty continuously
because they don't ectract as many nutrients from
the food they eat.
17
(No Transcript)
18
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie)
19
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) 1. Abiotic
20
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) 1. Abiotic TEMP
seasonal extremes - continental climate limits
growing season to 120-300 days depending on
latitude and temperature extremes. RAINFALL
Summer rain is predictably seasonal. Rainfall is
too low to leach cations from soil but can be
high enough to support significant plant
productivity. EVAPOTRANSPIRATIONAL STRESS high,
especially in dry season selects for C4 grasses
but C3 grasses still plentiful LIGHT Never
limiting, no winter and no big trees creating
shade SOILS deep and rich DISTURBANCE fire -
selects for grasses NUTRIENTS and CYCLING moist
grasslands are richest soils on Earth, rich in
nutrients and organics
21
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) 1. Abiotic 2.
Biota
22
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) 1. Abiotic 2.
Biota The height and density of grasses
correlates with rainfall, which changes the soil
conditions.
increasing rainfall
23
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) 1. Abiotic 2.
Biota The height and density of grasses
correlates with rainfall, which changes the soil
conditions. Perennial C4 grasses dominate.
24
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) 1. Abiotic 2.
Biota The height and density of grasses
correlates with rainfall, which changes the soil
conditions. Perennial C4 grasses dominate.
Again, large grazers and predators dominate the
food webs.
25
(No Transcript)
26
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) C. ArcticTundra
ALPINE
ARCTIC
27
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) C. Arctic Tundra 1.
Abiotic
28
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) C. Arctic Tundra 1.
Abiotic TEMP Cold most of the year, with a
growing season less than 100 days. The summer
does have long days, but light intensities are
still low due to oblique angle. RAINFALL
Precipitation is very low, less than 25cm/year.
EVAPOTRANSPIRATIONAL STRESS high, largely due
to desiccating effects of dry, strong cold winds
and water frozen as ice most of year. LIGHT
Limiting most of year growing season very short
SOILS shallow just above permafrost boggy in
summer very slow decomposition - mats of peat
that transfer little nitrogen to soil
29
(No Transcript)
30
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) C. Arctic Tundra 1.
Abiotic TEMP Cold most of the year, with a
growing season less than 100 days. The summer
does have long days, but light intensities are
still low due to oblique angle. RAINFALL
Precipitation is very low, less than 25cm/year.
EVAPOTRANSPIRATIONAL STRESS high, largely due
to desiccating effects of dry, strong cold winds
and water frozen as ice most of year. LIGHT
Limiting most of year growing season very short
SOILS shallow just above permafrost boggy in
summer very slow decomposition - mats of peat
that transfer little nitrogen to soil
DISTURBANCE winter, freez-thaw cycles, storms,
exposure
31
(No Transcript)
32
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) C. Arctic Tundra 1.
Abiotic TEMP Cold most of the year, with a
growing season less than 100 days. The summer
does have long days, but light intensities are
still low due to oblique angle. RAINFALL
Precipitation is very low, less than 25cm/year.
EVAPOTRANSPIRATIONAL STRESS high, largely due
to desiccating effects of dry, strong cold winds
and water frozen as ice most of year. LIGHT
Limiting most of year growing season very short
SOILS shallow just above permafrost boggy in
summer very slow decomposition - mats of peat
that transfer little nitrogen to soil
DISTURBANCE winter, freez-thaw cycles, storms,
exposure NUTRIENTS and CYCLING soils nutrient
poor and shallow
33
peeling back the soil and vegetation to the top
of the permafrost
34

• III. Grasslands
• A. Shrub Forest - Savannah
• B. Temperate Grassland (Prairie)
• C. Arctic Tundra
• 1. Abiotic
• 2. Biota
• No trees - above treeline.

35
III. Grasslands A. Shrub Forest - Savannah B.
Temperate Grassland (Prairie) C. Arctic Tundra 1.
Abiotic 2. Biota No trees - above treeline.
Perennial grasses, mosses, and lichens dominate
the growing season is even too short for annual
herbs to really get going.
36

• III. Grasslands
• A. Shrub Forest - Savannah
• B. Temperate Grassland (Prairie)
• C. Arctic Tundra
• 1. Abiotic
• 2. Biota
• No trees - above treeline.
• Perennial grasses, mosses, and lichens dominate
  the growing season is even too short for annual
  herbs to really get going.
• Mammals tend to remain all year, relying on thick
  fur to weather winters. Some migration into the
  boreal forest does occur.

37

• III. Grasslands
• A. Shrub Forest - Savannah
• B. Temperate Grassland (Prairie)
• C. Arctic Tundra
• 1. Abiotic
• 2. Biota
• 3. Alpine Tundra

38

• III. Grasslands
• A. Shrub Forest - Savannah
• B. Temperate Grassland (Prairie)
• C. Arctic Tundra
• 1. Abiotic
• 2. Biota
• 3. Alpine Tundra
• Elevational treelines vary with latitude, being
  900m at 65N, 2100m at 49N, 3300m at 40N, and
  4200m at 19N.

39

• III. Grasslands
• A. Shrub Forest - Savannah
• B. Temperate Grassland (Prairie)
• C. Arctic Tundra
• 1. Abiotic
• 2. Biota
• 3. Alpine Tundra
• Elevational treelines vary with latitude, being
  900m at 65N, 2100m at 49N, 3300m at 40N, and
  4200m at 19N.
• Soils lack permafrost but are thin and "new".
  Well drained (water runs downslope and does not
  pool) and summer droughts can occur.
• Dominant plants are perennial grasses and cushion
  plants.

40
(No Transcript)
41

• III. Grasslands
• IV. Deserts

42

• III. Grasslands
• IV. Deserts
• 1. Abiotic
• TEMP Temperatures can vary dramatically,
  depending on time of day, time of year, and
  latitude. Below freezing temperatures are
  possible in high latitude deserts.
• RAINFALL The common limiting variable is water -
  deserts have less than 25cm/year, on average. In
  warm deserts, the potential evaporation is much
  greater than the precipitation. In Phoenix, AZ,
  potential evapotranspiration is 130 cm a year,
  but rainfall is only 18 cm/year.
• EVAPOTRANSPIRATIONAL STRESS very high
  desiccating conditions exceed rainfall
• LIGHT not limiting during growing season
• SOILS little vegetation cover and slow
  decomposition mean little organic inputs - very
  patchy (under bushes). Otherwise, mineral soil is
  exposed (lithosol). Rainfall does not generate
  enough soil mositure to leach cations capillary
  action may even bring them near to surface and
  form a calcium and magnesium hardpan called
  caliche. These salts exacerbate desiccation.
• DISTURBANCE desiccation, temperature extremes,
  severe drought, fire
• NUTRIENTS and CYCLING very poor

43
(No Transcript)
44

• III. Grasslands
• IV. Deserts
• 1. Abiotic
• 2. Biota

45

• III. Grasslands
• IV. Deserts
• 1. Abiotic
• 2. Biota
• Xerophyllic plants adapted to extreme drought
  stress dominate (CAM plants)

46
III. Grasslands IV. Deserts 1. Abiotic 2.
Biota CAM plants (cacti). In deserts where it's
REALLY dry, you can't even have your stomates
open AT ALL during the day... as son as the sun
comes up, it's hot. So, CAM plants keep their
stomates closed in the day, and they only use CO2
stored from the previous evening.
NIGHT - Stomates open, CO2 absorbed and ficed
into a C4 molecule
6(CO2)
6(C6)
6(C5)
C4
C6 (Glucose)
C3
5(C6)
47
III. Grasslands IV. Deserts 1. Abiotic 2.
Biota NIGHT - Stomates open, CO2 absorbed and
fixed into a C4 molecule DAY Stomates closed, C4
is used and CO2 is released and Glucose is
made....this can only be done in the daylight
when ATP ans NADP are made with the light
reaction.
6(CO2)
6(C6)
6(C5)
C4
C6 (Glucose)
C3
C3
5(C6)
48

• III. Grasslands
• IV. Deserts
• 1. Abiotic
• 2. Biota
• Xerophyllic plants adapted to extreme drought
  stress dominate (CAM plants)
• strong diurnal patterns in animal and plant
  activity (CAM)

49

• III. Grasslands
• IV. Deserts
• 1. Abiotic
• 2. Biota
• Xerophyllic plants adapted to extreme drought
  stress dominate (CAM plants)
• strong diurnal patterns in animal and plant
  activity (CAM)
• Plant density tightly linked to water
  availability.

50

• III. Grasslands
• IV. Deserts
• V. Summary - Terrestrial Biomes
• NET PRIMARY PRODUCTIVITY (total photosynthesis -
  respiration)

51

• III. Grasslands
• IV. Deserts
• V. Summary - Terrestrial Biomes
• NET PRIMARY PRODUCTIVITY (total photosynthesis -
  respiration)
• Take home messages....
• 1) per unit area, forests are more productive
  than grasslands, which are more productive that
  the open ocean (though REEFS are very
  productive!!)

52

• III. Grasslands
• IV. Deserts
• V. Summary - Terrestrial Biomes
• NET PRIMARY PRODUCTIVITY (total photosynthesis -
  respiration)
• Take home messages....
• 2) multiplying by the area of the biome, we see
  the whole productivity of the biome as a
  percentage of the Earth's productivity...

53

• III. Grasslands
• IV. Deserts
• V. Summary - Terrestrial Biomes
• NET PRIMARY PRODUCTIVITY (total photosynthesis -
  respiration)
• Take home messages....
• 2) Rainforests and the open ocean are responsible
  for over 40 of the planet's productivity.... why
  is this important?

54

• III. Grasslands
• IV. Deserts
• V. Summary - Terrestrial Biomes
• NET PRIMARY PRODUCTIVITY (total photosynthesis -
  respiration)
• Take home messages....
• ... because humans and all other organisms are
  dependent on the NET PRIMARY PRODUCTIVITY... it
  is the base of our food pyramids...

carnivores
HERBIVORES
NET PRIMARY PRODUCTIVITY
55
I. What is Ecology?
56
I. What is Ecology? A. Definitions
?
57
I. What is Ecology? A. Definitions "The
scientific study of the distribution and
abundance of organisms, and their interactions
with the environment."
58
I. What is Ecology? II. Ecological Interactions
59
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
60
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
1. Places differ with respect to climate and
soil. Organisms will be able to tolerate some
conditions and not others, based on their
fundamental physiology.
61
 
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
2. Tolerance Limits and Zones of Tolerance
optima
tolerance
tolerance
intolerance
intolerance
performance (met rate, growth, population growth
environmental variable
high
low
62
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
2. Tolerance Limits and Zones of Tolerance 3.
Leibigs law of the minimum distribution will be
limited by the factor for which the organism has
the narrowest range of tolerance
63
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
2. Tolerance Limits and Zones of Tolerance 3.
Leibigs law of the minimum distribution will be
limited by the factor for which the organism has
the narrowest range of tolerance 4. But, it also
depends on the degree to which the factors VARY
over time. A species may have a narrow range of
tolerance for a variable, but if that variable
doesn't change much, it won't affect the species
distribution.
64
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
2. Tolerance Limits and Zones of Tolerance 3.
Leibigs law of the minimum distribution will be
limited by the factor for which the organism has
the narrowest range of tolerance 4. But, it also
depends on the degree to which the factors VARY
over time. A species may have a narrow range of
tolerance for a variable, but if that variable
doesn't change much, it won't affect the species
distribution. 5. Can easily envision
2-dimensional space defining the conditions of
water and temperature, for instance, under which
a species can survive.
65
 
performance
temperature
soil moisture
66
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
5. Can easily envision 2-dimensional space
defining the conditions of water and temperature,
for instance, under which a species can
survive. 6. If you include 3, 4, ....'n'
dimensions, you define the "fundamental niche"
Obviously, ecologists aren't interested in all
variables, only the ones that 'limit' a species
distribution or performance in a given area. This
variable (or set of variables) is called the
'limiting variable'.
67
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment
5. Can easily envision 2-dimensional space
defining the conditions of water and temperature,
for instance, under which a species can
survive. 6. If you include 3, 4, ....'n'
dimensions, you define the "fundamental niche"
Obviously, ecologists aren't interested in all
variables, only the ones that 'limit' a species
distribution or performance in a given area. This
variable (or set of variables) is called the
'limiting variable'. 7. Niches change with life
history, acclimation, and adaptation.
68
I. What is Ecology? II. Ecological Interactions
A. With the Abiotic Environment B. With
Other Organisms

69
Study questions 1. Why do grasslands dominate in
continental climates? 2. How does C4
photosynthesis work? Why is this beneficial in
dry environments? 3. Arctic tundra is water
logged and acidic... why? 4. What is permafrost,
and how might global warming affect it in a
non-linear way? 5. How does alpine tundra differ
from arctic tundra? 6. Why are desert soils low
in nutrients? (two reasons). 7. Why are desert
soils salty, and what effect does this have on
plants? 8. What is a "fundamental niche"?