Secondary
Compounds
Germination
and Seedling
Establishment
Photosynthesis
Life Cycles
and
Phenology
Seasonal
Growth Rates
You are here
Seasonality and
Life Cycles
Plant Physiology
Carbohydrates
and
Allocation
Water and
Nutrients
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing and
Plant Growth
Grazing
Resistance
Grazing
Optimization
Morphology
Reproduction
Shrub
Anatomy
RANGE PLANT GROWTH AND DEVELOPMENT
Life Cycles
and
Phenology
You are here
Seasonality and
Life Cycles
Seasonality and Life Cycles
 Terminology
 Life Cycles
 Seasonal growth rates
 Forage Quality
 RDM
Seasonal
Growth Rates
Forage
Quality
RDM
READING AND REFERENCES
Seasonality and
Life Cycles
SEASONALITY & LIFE CYCLES



The Phenology Handbook, pg 1-15
George et al. 2001. Annual Range Forage Production
George and Bell. 2001. Using Stage of Maturity……..
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SEASONALITY & LIFE CYCLES
Plant Physiology
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




Terminology
Life Cycles
Forage Quality
Seasonal growth rates
RDM
Seasonality and
Life Cycles
TERMINOLOGY
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
Annual

Perennial
Seasonality and
Life Cycles
TERMINOLOGY
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Grass: monocot, most
are not woody
Forb: dicot, non-woody

Shrub
Dicot, woody
TERMINOLOGY
Seasonality and
Life Cycles
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

PHENOLOGY is the science
that measures the timing of
life cycle events for plants,
animals, and microbes, and
detects how the environment
influences the timing of those
events.
In the case of flowering plants,
these life cycle events, include
leaf budburst, first flower, last
flower, first ripe fruit, seed set,
leaf shedding, others.
SEASONALITY & LIFE CYCLES
Plant Physiology
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




Terminology
Life Cycles
Forage Quality
Seasonal growth rates
RDM
LIFE CYCLES
Seasonality and
Life Cycles
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Seasonality and
Life Cycles
ANNUAL LIFE CYCLES
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
Annuals


Germination
Vegetative







Seedling
establishment
Leaf growth
Winter growth is slow
Growth accelerates
in spring
Flowering
Seed Set, Drying
Dry and Die
Seasonality and
Life Cycles
ANNUAL LIFE CYCLE CALENDAR
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N
D
J
F
M
A
M
Germination & Seedling
Establishment
Rapid Vegetative
Slow Vegetative Growth
Growth
J
J
A
S
O
Little or No Vegetative Growth
Tiller Development
Flowering
Seed Development
Seed Set
Drying Stems &
Leaves
Dry & Dead Stems & Leaves
Timing of phenological events
Seasonality and
Life Cycles
PERENNIAL LIFE CYCLES
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
Perennials



Lives several years
Sexual reproduction
Vegetative reproduction







Stolons and Rhizomes
Winter dormancy
Dry season dormancy
Vegetative phase
Flowering
Seed set and dispersal
Dormancy
PERENNIAL LIFE CYCLE CALENDAR
Seasonality and
Life Cycles
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N
D
J
F
M
A
M
J
J
A
Dormant or Slow Vegetative Growth Rapid Vegetative Growth
Dormant
Dormant
Tiller Development
Carbohydrate Use
Apical Meristems Near Soil Surface
S
O
Slow Vegetative
Growth
Tiller Development
Carbohydrate Storage
Flower Stems
Elongate
Flowering
Seed
Development
Seed Set
Drying Stems &
Leaves
Dry & Dead
Stems &
Leaves
Timing of phenological events
PHENOLOGY AND LIFE CYCLES
Seasonality and
Life Cycles
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Phenological events
SEASONALITY & LIFE CYCLES
Plant Physiology
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




Terminology
Life Cycles
Forage Quality
Seasonal growth rates
RDM
PHENOLOGY AND FORAGE QUALITY
Seasonality and
Life Cycles
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Crude protein decreases in annual grasses with stage of maturity
(see ANR Publications 8019 and 8022)
SEASONALITY & LIFE CYCLES
Plant Physiology
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




Terminology
Life Cycles
Forage Quality
Seasonal growth rates
RDM
Seasonality and
Life Cycles
SEASONAL GROWTH RATES
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Average Monthly Peak Standing Crop at UC SFREC
3500
lbs/ac
3000
2500
2000
1500
1000
500
0
D1
J1
F1
M1
A1
M1 Peak
http://groups.ucanr.org/sierrafoothill/files/67089.pdf
Seasonality and
Life Cycles
SEASONAL GROWTH RATES
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Growth rates of perennials in northeastern
California
1400
1200
1000
lbs/ac

800
600
400
200
0
1-Feb
1-Mar
1-Apr
1-May
1-Jun
1-Jul
SEASONALITY & LIFE CYCLES
Plant Physiology
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




Terminology
Life Cycles
Seasonal growth rates
Forage Quality
RDM
LITTER: RESIDUAL DRY MATTER
Seasonality and
Life Cycles
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Moderate grazing results in
recommended RDM levels
Light grazing results in high
RDM levels
Heavy grazing results in low
RDM levels
SUMMARY
Seasonality and
Life Cycles
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
In this section you have learned the differences
between annual and perennial life cycles and
how plant growth rates and forage quality
change as range and pasture plants move
through their life cycle.
Secondary
Compounds
Germination
and Seedling
Establishment
Photosynthesis
Life Cycles
and
Phenology
Seasonal
Growth Rates
You are here
Seasonality and
Life Cycles
Plant Physiology
Carbohydrates
and
Allocation
Water and
Nutrients
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing and
Plant Growth
Grazing
Resistance
Grazing
Optimization
Morphology
Reproduction
Shrub
Anatomy
RANGE PLANT GROWTH AND DEVELOPMENT
Morphology
 Grass Anatomy
 Forb Anatomy
 Shrub Anatomy
 Reproduction
Grass
Anatomy
Forb
Anatomy
Morphology and
Development
Shrub
Anatomy
Reproduction
You are here
READING AND REFERENCES



MORPHOLOGY
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Introduction and Developmental Morphology Sections.
Skinner and Moore. Growth and Dev of Forage Plants
How Grass Grows
MORPHOLOGY
Plant Physiology
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



Grass Anatomy
Forb Anatomy
Shrub Anatomy
Reproduction
GRASS ANATOMY
Morphology and
Development
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




Please review “How Grass Grows” at the link below.
Overview of the Grass Plant
 Shoot Development
 Crown
 Leaf Formation
 Leaf Expansion Dynamics
 Tillering
 Rhizome and Stolon Development
 Flowering
Root Development
Germination Process
Seasonal Development
http://www.files.ahnrit.vt.edu/files/flash/howgrassgrows/howgrassgrows.swf
GROWING POINTS
Morphology and
Development
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





Apical meristems (flower)
Axillary buds (give rise to tillers,
rhizomes and stolons)
Intercalary meristems or collar
(leaf expansion)
Some growing points become
elevated as the growing season
progresses.
Buds near the ground are less
likely to be grazed
Delaying bud elevation reduces
risk of bud removal by grazing
GROWING POINTS
Morphology and
Development
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





Apical meristems (flower)
Axillary buds (give rise to tillers,
rhizomes and stolons)
Intercalary meristems or collar
(leaf expansion)
Some growing points become
elevated as the growing season
progresses.
Buds near the ground are less
likely to be grazed
Delaying bud elevation reduces
risk of bud removal by grazing
GROWING POINTS
Morphology and
Development
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





Apical meristems (flower)
Axillary buds (give rise to tillers,
rhizomes and stolons)
Intercalary meristems or collar (leaf
expansion)
Some growing points become elevated
as the growing season progresses.
Buds near the ground are less likely to
be grazed
Delaying bud elevation reduces risk of
bud removal by grazing
GROWING POINTS
Morphology and
Development
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





Apical meristems (flower)
Axillary buds (give rise to tillers,
rhizomes and stolons)
Intercalary meristems or collar (leaf
expansion)
Some growing points become elevated
as the growing season progresses.
Buds near the ground are less likely to
be grazed
Apical
Delaying bud elevation reduces risk of meristem
rising
bud removal by grazing
VEGETATIVE PHASE
Morphology and
Development
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

In the vegetative phase,
shoots consist
predominantly of leaf
blades.
Leaf blade collars remain
nested in the base of the
shoot and there is no
evidence of sheath
elongation or culm
development.
ELONGATION (TRANSITION) PHASE
Morphology and
Development
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
Floral induction - Apical meristems is
gradually converted from a vegetative
bud to a floral bud.

During the transition phase, leaf
sheaths begin to elongate, raising the
meristematic collar zone to a grazable
height.

Culm internodes also begin elongation
in an "un-telescoping" manner
beginning with the lowermost
internode thereby raising the
meristematic zone (floral bud and leaf
bases) to a vulnerable position.
REPRODUCTIVE PHASE
Morphology and
Development
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


The flowering phase begins
with the conversion from
vegetative to floral bud.
Much of this is unseen until
the emergence of the seed
head from the sheath of the
flag leaf (boot stage).
Within a few days,
individual florets within the
seed head are ready for
pollination.
Apical
meristem
rising
MORPHOLOGY
Plant Physiology
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



Grass Anatomy
Forb Anatomy
Shrub Anatomy
Reproduction
FORB ANATOMY
Morphology and
Development
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FORB GROWING POINTS
Morphology and
Development
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MORPHOLOGY
Plant Physiology
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



Grass Anatomy
Forb Anatomy
Shrub Anatomy
Reproduction
Morphology and
Development
SHRUB ANATOMY
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
Coast live oak resprouts

Chamise resprouts
MORPHOLOGY
Plant Physiology
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



Grass Anatomy
Forb Anatomy
Shrub Anatomy
Reproduction
REPRODUCTION
Morphology and
Development
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



Long Day Plants
Short Day Plants
Sexual Reproduction (flowers and seeds)
Vegetative Reproduction (stolons, rhizomes)
REPRODUCTION LONG DAY PLANTS



Some plants are long-day plants
and others are short-day plants.
The long-day plants reach the
flowering phenological stage after
exposure to a critical photoperiod
and during the period of increasing
daylight between mid April and mid
June.
Generally, most cool-season plants
with the C3 photosynthetic pathway
are long-day plants and reach
flower phenophase before 21 June.
Morphology and
Development
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REPRODUCTION
SHORT DAY PLANTS




Short-day plants are induced into flowering
by day lengths that are shorter than a critical
length and that occur during the period of
decreasing day length after mid June.
Short-day plants are technically responding
to the increase in the length of the night
period rather than to the decrease in day
length.
Generally, most warm-season plants with the
C4 photosynthetic pathway are short-day
plants and reach flower phenophase after
21 June.
The annual pattern in the change in daylight
duration follows the calendar and is the
same every year for each region.
Morphology and
Development
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REPRODUCTION
Morphology and
Development
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

Plant populations persist through
both asexual (vegetative)
reproduction and sexual
reproduction.
The frequency of true seedlings
produced from seed is low in
established grasslands and
occurs only during years with
favorable moisture and
temperature conditions in areas
of reduced competition from older
tillers, and when resources are
easily available to the growing
seedling.
REPRODUCTION
Morphology and
Development
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

SEXUAL
Sexual reproduction is necessary for a population to maintain
the genetic diversity enabling it to withstand large-scale
changes.
However, production of viable seed each year is not necessary
to the perpetuation of a healthy grassland.
REPRODUCTION
SEXUAL


Reproductive shoots are
adapted for seed production
rather than for tolerance to
defoliation
Grass species that produce a
high proportion of
reproductive shoots are less
resistant to grazing than are
those species in which a high
proportion of the shoots
remains vegetative.
Morphology and
Development
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REPRODUCTION
ASEXUAL OR VEGETATIVE




Vegetative growth is the dominant form of
reproduction in semiarid and mesic grasslands
Annual plants are dependent on seed production
each year for survival.
Short-lived perennials depend on seed production.
Long-lived perennials rely more on vegetative
reproduction.
Morphology and
Development
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TILLERING
Morphology and
Development
REPRODUCTION
ASEXUAL OR VEGETATIVE



Bunch grasses spread by the production
of tillers.
Stoloniferous grasses spread by lateral
stems, called stolons, that creep over
the ground and give rise to new shoots
periodically along the length of the
stolon.
Rhizomatous grasses spread from below
ground stems known as rhizomes.
Morphology and
Development
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SUMMARY
Morphology and
Development
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.
In this section you learned about plant growing points, how
plants grow, phases of plant growth and reproduction. You
learned that vegetative reproduction in the form of tillers,
stolons and rhizomes are more important than reproduction
via seeds in most grasslands. You also learned that buds
close to the ground are less vulnerable to grazing than when
they are elevated.
Secondary
Compounds
Germination
and Seedling
Establishment
Photosynthesis
Life Cycles
and
Phenology
Seasonal
Growth Rates
You are here
Seasonality and
Life Cycles
Plant Physiology
Carbohydrates
and
Allocation
Water and
Nutrients
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing and
Plant Growth
Grazing
Resistance
Grazing
Optimization
Morphology
Reproduction
RANGE PLANT
GROWTH AND DEVELOPMENT
Shrub
Anatomy
Secondary
Compounds
Photosynthesis
Germination
and Seedling
Establishment
Plant Physiology
Water and
Nutrients
Carbohydrates
and
Allocation
Plant Physiology
 Germination &
Seedling
Establishment
 Photosynthesis
 Carbohydrates and
Carbohydrate
Allocation
 Water and Nutrients
 Secondary
Compounds
READING AND REFERENCES
PLANT PHYSIOLOGY




McKell, C.M. 1974. Morphogenesis and management of
annual range plants in the United States. Pg 111-116.
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Grazing Resistance Section.
Waller and Lewis. 1979. Occurrence of C3 and C4
photosynthetic pathways in North American grasses.
Carbohydrate Reserves: What you learned may be wrong.
PLANT PHYSIOLOGY
Plant Physiology
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




Germination and Seedling Establishment
Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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
See Anatomy




Seed Coat
Embryo
Endosperm (food
reserves)
Seed coat (pericarp)
Variable seed
production

Empty seeds
Empty Seeds
GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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PHOTOTROPISM
Plant Physiology
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GERMINATION & SEEDLING
ESTABLISHMENT




Oxygen is required for
respiration during
germination.
Oxygen is found in soil pore
spaces but if a seed is
buried too deeply within the
soil or the soil is
waterlogged, the seed can
be oxygen starved.
Some seeds have
impermeable seed coats
sometimes called hard
seed.
Hard seed is common in
legumes
Plant Physiology
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GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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


Temperature also influences
germination.
Seeds from different
species and even seeds
from the same plant
germinate over a wide range
of temperatures.
Seeds often have a
temperature range within
which they will germinate,
and they will not do so
above or below this range.
GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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



Some seeds require exposure to
cold temperatures (vernalization)
to break dormancy.
Seeds in a dormant state will not
germinate even if conditions are
favorable.
Some seeds will only germinate
following hot weather and others
exposed to hot temperatures
during a forest fire which cracks
their seed coats.
Some seeds need to pass through
an animal's digestive tract to
weaken the seed coat enough to
allow the seedling to emerge.
GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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


Variability in the rate of
germination exists between
and within species.
Seed size has been shown
to be a critical factor in
promoting seedling vigor.
In legumes and other forbs,
seed coat hardness or
impermeability often retards
germination but spreads
germination over years
which is a survival
advantage for the species.
GERMINATION & SEEDLING
ESTABLISHMENT
Plant Physiology
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


On annual rangelands estimates
of germinable seed exceed
20,000 per m2.
On annual rangelands the
number of plants early in the
growing season has been
reported to vary from 20 to nearly
100 per square inch.
Considerable reduction in this
number takes place as the
season progresses. The lost
seedlings decay and provide a
flush of nutrients early in the
growing season.
GERMINATION & SEEDLING
ESTABLISHMENT



Rapid root growth is
fundamental to establishment
and development of annual
rangeland plants.
Individual plants and species
may gain an advantage over
competitors if they exhibit rapid
root growth and are able to
maintain both rapid root and top
growth.
Annual grasses frequently
exhibit root growth rates greater
than native perennial grasses
Plant Physiology
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Annual grass (cheatgrass) roots
(b) grew faster in this study than
blue bunch wheatgrass (native
perennial ) roots (a) (Harris
1977, JRM)
PLANT PHYSIOLOGY
Plant Physiology
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




Germination and Seedling Establishment
Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
PHOTOSYNTHESIS
Plant Physiology
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CO2 + H2O
Sunlight
Chlorophyll
CH2O + O2
FOUR FUNDAMENTAL CONCEPTS
Plant Physiology
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



Plants are the only source of energy for grazing animals.
The formation of sugars, starches, proteins and other foods
is dependent on photosynthesis.
Plants do not get food from the soil. They obtain raw
materials needed for photosynthesis and subsequent food
production
When leaves are removed from plants, food-producing
capacity is reduced.
PHOTOSYNTHESIS
Plant Physiology
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To learn more about Photosynthesis:
http://www.youtube.com/watch?v=_wO9f3
ER17M
PHOTOSYNTHETIC RATE
Plant Physiology
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Factors that influence photosynthetic rate
1. Leaf area
2. Light intensity and quality
3. CO2 content of the air
4.
5.
6.
7.
Physiological efficiency
Soil nutrients
Water supply
Temperature
LEAF AREA AND LIGHT INTENSITY
Plant Physiology
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Relationship between light interception and leaf area (Brougham 1956)
PHOTOSYNTHESIS & LIGHT INTENSITY
Plant Physiology
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Lightly grazed
Closely grazed
PHOTOSYNTHESIS & LEAF AREA
Plant Physiology
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(Parsons et al. 1983)
PRODUCTION & LEAF AREA
Plant Physiology
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Relationship between leaf area and herbage yield (Brougham 1956)
GROSS & NET PRIMARY PRODUCTION
Plant Physiology
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
NPP=GPP - R
GPP and NPP
increase as leaves
are added until
upper leaves
begin shading
lower leaves then
R increases
resulting in
decrease in NPP
Gross & Net Production
GPP
Photosynthesis (% of
maximum GPP)

NPP
R
100
80
60
40
20
0
0
1
2
3
4
5
6
Leaf Area Index
7
8
9
10
STOMATES AND WATER RELATIONS
Plant Physiology
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Stomate
Guard Cells
WATER RELATIONS
Plant Physiology
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



Water required for
photosynthesis
Lost through stomates
(transpiration)
Arid and semi-arid lands
frequently subjected to water
stress
Drought tolerant
PHOTOSYNTHETIC PATHWAYS
C3, C4 & CAM Pathways
Plant Physiology
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C3 PHOTOSYNTHESIS
Plant Physiology
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




C3 because CO2 is first incorporated
into a 3-carbon compound.
Stomata are open during the day.
Photosynthesis takes place
throughout the leaf.
Adaptive Value:
 more efficient than C4 and CAM
plants under cool and moist
conditions and,
 under normal light conditions.
Most plants are C3.
C4 PHOTOSYNTHESIS
Plant Physiology
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





CO2 is first incorporated into a 4-carbon compound
Stomata are open during the day.
Photosynthesis takes place in inner bundle sheath
cells
Adaptive Value:
 Photosynthesizes faster than C3 plants under
high light intensity and high temperatures.
 Better water use efficiency than C3 because
CO2 uptake is faster and so does not need to
keep stomata open as much (less water lost by
transpiration) for the same amount of CO2 gain
for photosynthesis
C4 plants include several thousand species in at
least 19 plant families
Examples: fourwing saltbush, corn, and many
summer annual plants
CAM PHOTOSYNTHESIS




Plant Physiology
Crassulacean Acid Metabolism (CAM)
Stomata open at night and are usually closed during
the day.
 The CO2 is converted to an acid and stored during
the night.
 During the day, the acid is broken down and the
CO2 is released for photosynthesis
Adaptive Value:
 Better Water Use Efficiency than C3 plants
 CAM-Idle
 When conditions are extremely arid, CAM plants
can just leave their stomata closed night and
day.
CAM plants include many succulents such as cactuses
and agaves and also some orchids and bromeliads
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COOL & WARM SEASON GRASSES
Plant Physiology
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Waller, S.S. and J.K. Lewis. 1979. Occurrence of C3 and C4
Photosynthetic Pathways in North American Grasses. Journal of Range
Management 32:12-28 for an review and list of C3 and C4 range plants.
ROOT GROWTH TEMPERATURES
Plant Physiology
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WATER USE EFFICIENCIES
C3 VS C4
Plant Physiology
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CO2 CONCENTRATION
Plant Physiology
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LIGHT, TEMPERATURE AND CO2
C3 VS C4:
Plant Physiology
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PLANT PHYSIOLOGY
Plant Physiology
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




Germination and Seedling Establishment
Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
REDUCED CARBOHYDRATE STORAGE
Plant Physiology
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Carbohydrates are the plant’s energy source
Energy needed for:
• Root replacement
• Leaf and stem
growth following
dormancy
• Respiration during
dormancy
• Bud formation
• Regrowth following
top removal
CARBON DISTRIBUTION/ALLOCATION
Plant Physiology
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CARBON DISTRIBUTION/ALLOCATION
Plant Physiology
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CARBON DISTRIBUTION/ALLOCATION
Plant Physiology
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CARBON DISTRIBUTION/ALLOCATION
Plant Physiology
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PLANT PHYSIOLOGY
Plant Physiology
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




Germination and Seedling Establishment
Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
WATER AND NUTRIENT UPTAKE
Plant Physiology
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For more information on plant water movement see these two videos:
http://www.youtube.com/watch?v=tRNe_UHw7F4
http://www.youtube.com/watch?v=umUn8D6gEOg&feature=related
AVAILABLE WATER
Plant Physiology
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NUTRIENT UPTAKE
Plant Physiology
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MYCORRHIZAE
Plant Physiology
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PLANT PHYSIOLOGY
Plant Physiology
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




Germination and Seedling Establishment
Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
SECONDARY COMPOUNDS
Plant Physiology
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Many secondary compounds are toxic to livestock and humans.
For more information see “Livestock-Poisoning Plants of California.
SECONDARY COMPOUNDS
TERPENES
Conifers accumulate monoterpenes
Plant Physiology
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SECONDARY COMPOUNDS
PHENOLICS



Plant Physiology
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Lignin
Flavenoids
Tannin
Tannins in oak leaves
isoflavenoids in legumes
SECONDARY COMPOUNDS
Plant Physiology
NITROGEN CONTAINING COMPOUNDS

Alkaloids

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Cynanogenic glycosides
SECONDARY COMPOUNDS
ALLELOPATHY
Plant Physiology
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SUMMARY
Plant Physiology
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In the plant physiology section you learned about germination and
seedling establishment, photosynthesis, carbohydrate storage and
allocation, plant water relations and nutrient uptake and secondary
compounds. You learned that fire and heat can influence germination
along with soil moisture and temperature. You also learned that
photosynthetic rate increases with leaf area to some optimum level and
then slows with continued increases in leaf area. You learned about
three photosynthetic pathways (C3, C4 and CAM) and their adaptive
value. You learned that carbohydrates produced during photosynthesis
are used for plant growth or stored to meet future needs. And finally you
learned about secondary compounds
Secondary
Compounds
Germination
and Seedling
Establishment
Photosynthesis
Life Cycles
and
Phenology
Seasonal
Growth Rates
You are here
Seasonality and
Life Cycles
Plant Physiology
Carbohydrates
and
Allocation
Water and
Nutrients
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing and
Plant Growth
Grazing
Resistance
Grazing
Optimization
Morphology
Reproduction
RANGE PLANT
GROWTH AND DEVELOPMENT
Shrub
Anatomy
Grazing and Plant Growth
 Grazing Effects
 Grazing Optimization
 Grazing Resistance
Grazing
Effects
Grazing and
Plant Growth
Grazing
Resistance
Grazing
Optimization
READING AND REFERENCES
GRAZING & PLANT GROWTH




Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Grazing Resistance Section.
Trlica, J. 2006. Grass Growth and Response to Grazing.
A quick lesson in plant structure, growth and regrowth for
pasture-based dairy systems.
Noy-Meir, I. 1993. Compensating growth of grazed plants and
its relevance to the use of rangelands.
GRAZING AND PLANT GROWTH
Grazing and
Plant Growth
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


Grazing Effects
Grazing Optimization
Grazing Resistance
GRAZING EFFECTS
Grazing and
Plant Growth
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 Detrimental Effects
 Growth Promoting Effects
DETRIMENTAL GRAZING EFFECTS
Grazing and
Plant Growth
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



Removal of photosynthetic
tissue
Reduced carbohydrate
storage
Reduced root growth
Reduced seed production
REDUCED LEAF AREA FOR PHOTOSYNTHESIS
Grazing and
Plant Growth
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Grazing can influence leaf area
1. Grazing that is too heavy can reduce leaf area and reduce
photosynthesis and carbohydrate production.
REDUCE GROWTH
Grazing and
Plant Growth
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Grow leaves,
stems, roots and
buds.
1. Heavy grazing can weaken root systems increasing moisture
stress
REDUCE GROWTH
Grazing and
Plant Growth
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Leaves, stems,
roots and other
plant parts
1. Heavy grazing can weaken root systems increasing moisture
stress
REDUCE GROWTH
Grazing and
Plant Growth
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Seed production
REDUCED CARBOHYDRATE STORAGE
Grazing and
Plant Growth
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Carbohydrates are the plant’s energy source
GRAZING EFFECTS
Grazing and
Plant Growth
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

Detrimental Effects
Growth Promoting Effects
GROWTH PROMOTING EFFECTS




Increased photosynthesis
Increased tillering
Reduced shading
Reduced transpiration
Grazing and
Plant Growth
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INFLUENCES ON GRAZING EFFECTS
Grazing and
Plant Growth
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1.
2.
3.
4.
Intensity
Timing
Frequency
Grazing of surrounding plants
LITTER
Grazing and
Plant Growth
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1.
2.
3.
4.
Decreases evapotranspiration
Moderates surface microclimate during germination and seedling
establishment
Slows surface runoff and increases infiltration
Protects soil from erosion
GRAZING TO CLOSE
Grazing too close reduces reserves
and slows recovery following grazing
Grazing and
Plant Growth
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DETRIMENTAL EFFECTS OF GRAZING
Grazing and
Plant Growth
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A
B
C



Plant A was allowed to grow for
three months without clipping.
Healthy root system
Plant B was clipped to 3 inches
every three weeks for 3
months. Healthy root system
Plant C was clipped to 1 inch
every week for 3 months. Very
weak root system and might not
survive a drought
SUMMARY
Grazing and
Plant Growth
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Negative effects of heavy grazing vs. possible effects
of light to moderate grazing on range plant physiology
Heavy Grazing:
 Decreased photosynthesis
 Reduced carbohydrate storage
 Reduced root growth
 Reduced seed production
 Reduced ability to compete with
ungrazed plants
 Reduce accumulation of litter or
mulch which decreases water
infiltration and retention, plus it
protects soil from erosion.
Light to Moderate Grazing:
 Increased plant productivity
 Increased tillering
 Reduced shading of lower leaves
 Reduced transpiration losses
 Reduced ability to compete with
ungrazed plants
 Reduction of excessive litter or
mulch that can physically or
chemically inhibit vegetative
growth. Excessive mulch
promotes pathogens and insects
that can damage forage plants.
GRAZING AND PLANT GROWTH
Grazing and
Plant Growth
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


Grazing Effects
Grazing Optimization
Grazing Resistance
GRAZING OPTIMIZATION
Grazing and
Plant Growth
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

There are levels of grazing that can result in
increased productivity
G.O. is a complex and sometime controversial
subject.
GRAZING OPTIMIZATION HYPOTHESIS
Grazing and
Plant Growth
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Grazing and
Plant Growth
GRAZING OPTIMIZATION HYPOTHESIS
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
NPP=GPP - R
GPP and NPP
increase as leaves
are added until
upper leaves
begin shading
lower leaves then
R increases
resulting in
decrease in NPP
Gross & Net Production
GPP
Photosynthesis (% of
maximum GPP)

NPP
R
100
80
60
40
20
0
0
1
2
3
4
5
6
Leaf Area Index
7
8
9
10
Grazing and
Plant Growth
GRAZING OPTIMIZATION
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




NPP=GPP - R
GPP and NPP increase as
leaves are added until
upper leaves begin shading
lower leaves then R
increases resulting in
decrease in NPP
Grazing reduces leaf area
G.O. says if grazing keeps
LAI near 4, NPP is
optimized.
May occur in some
species, more likely in
pasture.
Some species are
extremely susceptible to
grazing even at light
intensities.
Gross & Net Production
Photosynthesis (% of maximum
GPP)

GPP
NPP
R
100
80
60
40
20
0
0
1
2
3
4
5
6
7
Leaf Area Index
8
9
10
GRAZING OPTIMIZATION
Grazing and
Plant Growth
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C = ‘control’ no clipping
60 = 60% current annual growth removed
TB = terminal bud removed only 100 = 100% current annual growth removed
GRAZING OPTIMIZATION
Grazing and
Plant Growth
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MECHANISMS CONTRIBUTING TO
COMPENSATORY PLANT GROWTH
Grazing and
Plant Growth
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Herbivore-induced physiological processes
 Accelerated photosynthesis per unit leaf area
 Accelerated nutrient absorption per unit root mass
 Greater resource allocation to shoots
 Increased tiller initiation
 Improved water status
Herbivore-mediated environmental modification
 Increased irradiance on remaining leaves and young tillers
 Conservation of soil water following leaf area removal
 Accelerated rate of nutrient cycling
 Increased activity of decomposer organisms
GRAZING AND PLANT GROWTH
Grazing and
Plant Growth
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Grazing Effects
Grazing Optimization
Grazing Resistance
GRAZING RESISTANCE
Grazing and
Plant Growth
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GRAZING AVOIDANCE
Grazing and
Plant Growth
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

Mechanical
Biochemical
GRAZING TOLERANCE
Grazing and
Plant Growth
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PLANT MORPHOLOGY
 Grass, forb and shrub species produce viable axillary
buds have greater potential to regrow following grazing
 Grass, forb, and shrub species that protect meristems
have the potential to regrow quickly following grazing.
 Grasses that develop tillers at different times during
the grazing season tolerate grazing better than plants
that do not
GRAZING TOLERANCE
Grazing and
Plant Growth
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PLANT PHYSIOLOGY
 Ability to regrow quickly following grazing
 Ability to compete for water and nutrients enable
some plants to regrow more quickly
 In some plant grazing stimulates absorption of
nutrients. However, in many species removal of
leaves and stems decreases nutrient absorption.
 Ability to quickly move nutrients and carbohydrates
between roots and shoots
GRAZING RESISTANCE FACTORS
Grazing and
Plant Growth
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Grasses




Higher proportion of culmless (stemless)
shoots than species with low resistance
Greater delay in elongation of the apical
buds than species with low resistance
Sprout more freely from basal buds after
defoliation than species with low resistance.
Higher ratio of vegetative to reproductive
stems than species with low resistance.
GRAZING RESISTANCE FACTORS
Grazing and
Plant Growth
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Forbs
 Produce a large number of viable seeds
 Delayed elevation of growing points
 Poisons and chemical compounds that
reduce palatability
GRAZING RESISTANCE FACTORS
Grazing and
Plant Growth
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Shrubs
 Spines and thorns
 volatile oils and tannins that
reduce palatability
 Branches make removal of inner
leaves difficult
 Only current year’s growth is
palatable and nutritious for
most species.
GRAZING RESISTANCE OF FORAGE
Grazing and
Plant Growth
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Most to least resistant
1. Grasses
2. Shrubs
3. Forbs
*Many exceptions do occur.
SUMMARY
Grazing and
Plant Growth
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



In the final section you learned about grazing
and plant responses to grazing.
You learned that grazing can have detrimental
as well as growth promoting effects on plants.
We discussed the theory of grazing
optimization and some of the mechanisms
that can result in compensatory plant growth.
And finally we discussed mechanisms that
allow plants to resist the effects of grazing.
THE END: UNUSED SLIDES
READING AND REFERENCES
Seasonality and
Life Cycles
SEASONALITY & LIFE CYCLES



The Phenology Handbook, pg 1-15
George et al. 2001. Annual Range Forage Production
George and Bell. 2001. Using Stage of Maturity……..
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READING AND REFERENCES



MORPHOLOGY
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Introduction and Developmental Morphology Sections.
Skinner and Moore. Growth and Dev of Forage Plants
How Grass Grows
READING AND REFERENCES
PLANT PHYSIOLOGY




McKell, C.M. 1974. Morphogenesis and management of
annual range plants in the United States. Pg 111-116.
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Grazing Resistance Section.
Waller and Lewis. 1979. Occurrence of C3 and C4
photosynthetic pathways in North American grasses.
Carbohydrate Reserves: What you learned may be wrong.
READING AND REFERENCES
GRAZING & PLANT GROWTH




Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Grazing Resistance Section.
Trlica, J. 2006. Grass Growth and Response to Grazing.
A quick lesson in plant structure, growth and regrowth for
pasture-based dairy systems.
Noy-Meir, I. 1993. Compensating growth of grazed plants and
its relevance to the use of rangelands.
READING AND REFERENCES
PLANT PHYSIOLOGY




McKell, C.M. 1974. Morphogenesis and management of
annual range plants in the United States. Pg 111-116.
Briske, 1991. Chp 4. Dev. Morph and Phys of Grasses.
Grazing Resistance Section.
Waller and Lewis. 1979. Occurrence of C3 and C4
photosynthetic pathways in North American grasses.
Carbohydrate Reserves: What you learned may be wrong.
Morphology

Grass Anatomy



Forb Anatomy


Growing Points (buds, meristems)
Developmental Anatomy
Growing Points (buds, meristems)
Reproduction


Sexual
Asexual
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Plant Physiology
PLANT PHYSIOLOGY


Germination and Seedling Establishment
Photosynthesis





Return to Course Map
Factors that influence photosysnthesis
C3, C4, CAM Photosynthesis
Carbohydrates and Carbohydrate Allocation
Water and Nutrients
Secondary Compounds
Grazing and Plant Growth



Grazing Effects
Grazing Optimization
Grazing Resistance
Return to Course Map
Secondary
Compounds
Germination
and seeding
establishment
Photosynthesis
Life Cycles
And
Phenology
Seasonality and
Life Cycle
Plant Physiology
Water and
Nutrients
Seasonal
Growth Rates
Carbohydrates and
Carb. Allocation
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing
and Plant Growth
Grazing
Resistance
Grazing
Optimization
Morphology
Reproduction
You are here
PHYSIOLOGY AND MORPHOLOGY
OF RANGE PLANTS
Shrub
Anatomy
Secondary
Compounds
Germination
and seeding
establishment
Photosynthesis
Life Cycles
And
Phenology
Seasonality and
Life Cycle
Plant Physiology
Water and
Nutrients
You are here
Seasonal
Growth Rates
Carbohydrates and
Carb. Allocation
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing
and Plant Growth
Grazing
Resistance
Grazing
Optimization
Morphology
Reproduction
PHYSIOLOGY AND MORPHOLOGY
OF RANGE PLANTS
Shrub
Anatomy
Secondary
Compounds
Germination
and seeding
establishment
Photosynthesis
Life Cycles
And
Phenology
Seasonality and
Life Cycle
Plant Physiology
Water and
Nutrients
Seasonal
Growth Rates
Carbohydrates and
Carb. Allocation
Forage
Quality
RDM
Grass
Anatomy
Forb
Anatomy
Grazing
Effects
Grazing
and Plant Growth
Grazing
Resistance
You are here
Grazing
Optimization
Morphology
Reproduction
PHYSIOLOGY AND MORPHOLOGY
OF RANGE PLANTS
Shrub
Anatomy
CHAPTER 5: RANGE PLANT PHYSIOLOGY
1. Basic concepts of plant growth
2. Importance of carbohydrate reserves
3. Grazing effect on forage plants
4. Grazing resistance in grasses, forbs and shrubs
5. Grazing theory
a. Why palatable plants dominate rangelands with
good grazing management?
b. Why unpalatable plants dominate rangelands
under sustained heavy grazing (over grazing)?
A FEW BASIC PRINCIPLES CONCERNING THE INFLUENCE OF
GRAZING ON PLANTS
1. Plants must have leaves for photosynthesis.
2. Grazing has the least effect on plants during the dormant
season when they are photosynthetically inactive.
3. Grazing has the most severe effect on plants towards the
end of the growing season ( seed formation to seed
hardening) because the plant’s demands for
carbohydrates are higher and little time remains of
optimal temperature and moisture conditions for regrowth.
4. Grazing early in the growing season has less effect on
plants than late in the growing season because
considerable time remains when temperature and
moisture are optimal for regrowth.
WHY PLANTS MUST STORE CARBOHYDRATES
1. Root replacement and growth
2. Regeneration of leaves and stems after
dormancy
3. Respiration during dormancy
4. Bud formation
5. Regrowth after top removal by grazing.
PHOTOSYNTHESIS AND CARBOHYDRATES



Factors that influence photosysnthesis
C3, C4, CAM Photosynthesis
Carbohydrates and Carbohydrate Allocation
REPRODUCTION






Recruitment maintains plant community
Sexual Reproduction (flowers and seeds)
Vegetative Reproduction (stolons, rhizomes)
Annuals dependent on seed production
Short-lived perennials depend on seed production
Long-lived perennials rely more on vegetative reproduction.
Relationship between herbage dry matter and leaf area (Brougham 1956)
Increased photosynthesis
Increased tillering


Increased photosynthesis
Reduced transpiration
Reduced shading
Reduced transpiration
SUMMARY
EFFECTS OF LIGHT TO MODERATE GRAZING






Increased plant productivity
Increased tillering
Reduced shading of lower leaves
Reduced transpiration losses
Reduced ability to compete with ungrazed plants
Reduction of excessive litter or mulch that can physically or
chemically inhibit vegetative growth. Excessive mulch
promotes pathogens and insects that can damage forage
plants.
LIFE CYCLES
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Grazing and
Plant Growth
Bilbrough and Richards (1993)
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C = ‘control’ no clipping
60 = 60% current annual growth removed
TB = terminal bud removed only 100 = 100% current annual growth removed
Grazing and
Plant Growth
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Grazing and
Plant Growth
CARBOHYDRATE STORAGE
1.
2.
3.
4.
5.
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Root replacement and growth
Regeneration of leaves and stems after
dormancy
Respiration during dormancy
Bud formation
Regrowth after top removal by grazing.
We can probably delete this slide
GRAZING OPTIMIZATION
Grazing and
Plant Growth
Return to Course Map
Can probably delete this slide