Transcript Wind and Plants

Wind and Plants
WIND
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Wind has a major effect on agricultural and horticultural
production in NZ.
The prevailing winds are the most common winds in an
area.
NZ has a westerly wind pattern due to the earth’s spin.
This is changed in some areas by local features and
topography.
The ranges to the north and the mountains to the sough
turn the westerlies blowing towards Wellington into
northerlies as they flow through Cook Strait.
Strong moist northerly winds are common in Wellington
in spring, these damage blossom and new plant growth.
Wind
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Wind can be
measured using the
Beaufort scale.
Effects of wind on plant
productivity
Structural damage
 Lodging – flattening of cereal crops
 Cuticle damage on leaves – increases
water loss
 Broken branches
 Loss of petals on flowers
 Soil displacement causing soil erosion
Physiological damage
 Removal
of the layer of humid air around
the leaves which forms a protective
environment
 This causes:
Physiological damage
 Removal
of the layer of humid air around
the leaves which forms a protective
environment
 This causes:
High winds
remove humidity
Guard cell close
Increase in
transpiration
Water stress
CO2 cannot get in
Loss of
productivity
Less photosynthesis
For each of the following problems, make notes on
why it is not good. Wind can cause many problems
including:
 •Increased
as dust. _
erosion and removal of topsoil
 Lodging
of plants (when leaves become
entangled), making them difficult to
harvest
 Spreading
weed seeds, meaning
more costs of removal, or lower
income due to contamination of seed
crops.
 Reduced or damaged plant growth.
Damaged leaves do not carry out as
much photosynthesis. Flowers can be
damaged or blown off the plant. Winddamaged fruit does not store as well
and is less marketable. Cuticle
damage to leaves causes an increase
in water loss.
May bring salt spray or cause
spray drift
Upsetting insect movement.
Positive effects of the wind:
 Reduced
likelihood of frost
 Providing air movement that will dry the
outer leaves of a plant and therefore
prevent the growth of fungal diseases
 Assisting with the pollination of wind
pollinated plants
 Aid the drying of hay or grains before
harvest.
Activity on wind page 45
Correct order
 NZ
is a fairly windy place
 Wind is caused by
 An anticyclone
 Near the Earth’s
 Over elevated
Activity page 46
Answers for pg 46
Defoliation – stripped of leaves
Increased transpiration – leaf scorching
Abrasion – sand particles
Root damage – plant rocking in ground
Branches rub – scarring on branches
Plant distortion – plant leaning away
Lodging – the flattening of cereal crops
Reduction in pollination – loss of petals
Fruit loss – apple windfalls
Fruit loss, knocked off tree – pears
downgraded
Water loss – wilting of plant
Interference with insect movement – bees
cannot fly
Crop maturation – harvesting time later
Spraying – drifts from your property to
another
Lessens humidity – perfect disease free
crop
Reduces chance of frost – Large open areas
Increase in wind pollination – grass pollen
Guard cells – the stomata changes shape
Techniques to modify wind
 Artificial
Shelter
 Artificial windbreaks are expensive to set
up and are often used for high value or
short term crops.
 The strongest likely wind has to be
considered along with the soil type to
prevent the support posts blowing over.
Advantages
a
crop has instant shelter
 usually low maintenance
 takes up little space
 does not use up soil water and nutrients
 Does not have many of the disadvantages
of live shelter
Disadvantages
 require
replacing after several years due
to damage from light and wind
 not biodegradable creating disposal
problems
 expensive
 Does not have many of the advantages of
live shelter
Wind Break Design
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1. Permeable windbreaks are more effective at
reducing the force of wind than a solid barrier.
Live shelter should be triangular in vertical cross
section – this shape will reduce turbulence on
the leeward side and cast less shadow.
If the windbreak is impermeable, turbulence is a
possibility on the leeward side.
This is because the wind goes up and over the
impermeable object.
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2. Areas with heavy snow drifts are protected by
thicker shelter belts in the form of a small
woodlot.
 3. Distance between windbreaks should be no
more than 20 times the height of the windbreak
to prevent the build up of unsheltered
windspeed.
 Large shelter is often planted around perimeters
of blocks and subdivided with artificial shelter.
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4. Planting in double rows
to allow:
• reduction of draughts
below taller shelter.
• replacement trees for
older shelter belt.
5. In frost areas, where
shelter is planted across
valleys to prevent wind
tunnelling, either
deciduous shelter or gaps
are used to allow cold air
to drain away.
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Plant shelter across valleys to prevent
wind tunnelling
Run windbreaks north –south where
possible to reduce shading
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Student activities
 Page
88 - 89
Answers to student activity
1.
2.
3.
14% at 8m
Air temp – 16% at 1m, soil evap - -40%
at 3m, relative humidity – 8% at 1m, soil
moisture – 20% at 1m, wind speed -60%
at 4m
Air temp 2%, soil evap -25%, relat.
Humid -0%, soil moisture 3% and wind
speed -45%
4.