Climates and temperature

1
Climates and temperature

• Objectives
• Learn reasons for climatic variation at a macro
  level within a continent, region, county, etc.,
  and at a micro level within a single site, or
  even within a plant
• Learn how temperature influences the selection of
  plants for horticultural use
• Learn some of the techniques used by
  horticulturists to modify and control temperature

2
Major Components of Climate

• Temperature
• Winter
• Summer
• Moisture
• Rainfall (but also supplemental irrigation)
• Light
• Bright skies vs. cloudy, overcast skies
• Sun angles

3
Effects of temperature on bio-chemical and
physical processes

• Chemical reactions and physical properties are
  affected by temperature
• Biochemical reactions are accelerated at higher
  temps.
• an increase of 10C approximately doubles the
  rate of most chemical reactions
• Rates of diffusion, e.g. of gases, increase as
  temperatures rise

4
Effects of temperature on bio-chemical and
physical processes

• Evaporation increases at higher temperatures
• Solubility of compounds in water declines with
  lower temperatures
• Membrane properties change with temperature
• membranes are made of lipids, a.k.a. fats what
  happens to fats as they are heated and cooled?

5
Temperature affects many activities

• At the cellular level
• photosynthesis
• respiration
• cell expansion
• Therefore, temperature can influence many whole
  plant processes
• rate of growth
• dormancy of seeds and buds
• transpiration of water from roots to leaves

6
Why is climate important?

• Each plant species has an optimal level for every
  environmental factor, e.g. temperature

Growth Rate
Cold
Hot
Temperature
7
Classification of plants based on temperature
requirements

• Cool season crops
• peas, radish, tulips, KY bluegrass
• Warm season crops
• sweetcorn, pumpkins, canna lilies, Bermuda grass

8
Classification of plants based on temperature
requirements

• Classification system can also be used to
  describe plants that are grown in regions with
  different climatic conditions
• Tropical fruits
• Banana, coconut, mango, pineapple
• Subtropical fruits
• Avocado, date, citrus, coffee

9
Classification of plants based on temperature
requirements

• Classification system can also be used to
  describe plants that are grown in regions with
  different climatic conditions
• Temperate
• Only survive mild winter conditions
• Almond, European grape, blackberry
• Able to survive severe winters
• Apple, American grape, pear, strawberry

10
Why is climate important?

• As horticulturists, we use information about
  climate to
• Select sites for production of horticulture crops
• Select crops (species) that are well adapted to
  those sites

11
Macro-Climate

• Climate based on geographic region

12
Macro-climate Variation in winter temperature
Zone 3 -30 to - 40F
Zone 6 0 to -10F
Zone 5 -10 to -20F
Zone 7 10 to 0F
Average Annual Minimum Temperature (F) USDA
Hardiness Zone Map
13
Variation in temperature

• Can also be expressed in terms of frost-free
  days, or in number of heat units (product of
  average temperature and time)
• Why do temperatures vary?
• Proximity to Water
• Altitude
• Topography

14
Proximity to large bodies of water

• Water has high specific heat
• it requires a lot of energy to increase water
  temperature, therefore water changes temperature
  slowly
• Large bodies of water act as temperature
  buffers
• Land nearby such large water bodies is affected
  by the water temperature

15
Proximity to Large Bodies of
Water
Warm or cool winds blowing over a body of water
Make the adjacent land warmer or cooler
16
Proximity to large bodies of water
Sacramento
Nevada
San Francisco
60 miles
Pacific Ocean
California
17
Proximity to Large Bodies of
Water

• San Francisco
• January ave. temp 48.5F
• July ave. temp 62.2F
• Sacramento
• January ave. temp 45.3F
• July ave. temp 75.6F

18
Proximity to large bodies of water

• Eastern shore of Lake Michigan (within 10 miles
  of the lake) is a major area for fruit production
  - why???

19
Effect of Lake Michigan on temperatures

• Lake Michigan moderates the temperatures on
  adjacent land
• Mild temperatures in winter
• Moderate temperatures in summer
• Slow to warm in spring
• Bud development is slowed
• Reduces danger from late frosts
• Slower to cool down in fall
• Extends ripening period

20
Altitude

• Temperature decreases as altitude increases
• 1000 rise 2 - 4F decrease in temperature
• Sacramento, CA (30 ft. above sea level)
• January ave. temp 45.3F
• July ave. temp 75.6F
• Reno, NV (4,490 ft. above sea level)
• January ave. temp 32.2F
• July ave. temp 69.5F

21
Topography

• Hills / valleys
• Frost pocket
• Rain shadow
• Slopes alter exposure to solar radiation

22
Frost Pocket

• Cold air is more dense (heavier) than warm air
• Cold air sinks or settles
• On any given night, the low spot in the terrain
  will be colder than a nearby higher location

23
Frost Pocket
Cold Air
Plant your orchard here
Warmer
Frost Pocket
Colder
24
Rain Shadow

• Hills and mountains force air up to a higher
  elevation, where it is colder
• Lower temperatures mean the air can hold less
  moisture
• Rain falls on the side of the mountain exposed to
  prevailing winds
• The leeward side of the mountain is dry

25
Rain Shadow
Rising clouds lose moisture via rainfall
Drier conditions on leeward side, the Rain
Shadow
Moisture-laden prevailing winds
26
Slopes affect exposure to
solar radiation

• South side of hill - direct sunlight
• warmer
• dryer
• North side of hill - in the shadow, or less
  intense radiation
• cooler
• wetter

27
Slopes affect exposure to
solar radiation
South
North
Sun angle nearly perpendicular
Very oblique sun angle
Hotter Dryer
Cooler Wetter
28
Micro-climate within a plant or crop

• Fruit trees create small scale environments
  within the leafy canopy
• cooler
• lower light intensity
• This micro-climatic condition influences
• photosynthesis
• diseases
• fruit ripening

29
Micro-climates in the Built Landscape

• Buildings and other structures can also create
  micro-climates
• Surrounded courtyards PMU, Lynn Hall
• North sides of buildings AGAD, HORT

30
Manipulating temperature in horticulture

• Greenhouse environments
• Use a variety of heating systems
• Off-season production
• Extend growing season
• Fan and pad evaporative cooling (compare to
  getting cold after you get out of the shower)

31
Manipulating temperature in horticulture

• Cold frames, hot caps, cloches
• Prevent low temperature damage
• Extend growing season, especially in the spring

32
Manipulating temperature in horticulture

• Mulches are used in a variety of ways
• Black plastic mulch increases soil temperature,
  stimulating growth
• Mulches are also used to control weeds

33
Manipulating temperature in horticulture

• Mulches are used in many ways
• Organic (wood/bark chips etc.) mulches cool soil
  in summer, preserve moisture
• Mulches provide protection against low temps. in
  winter

34
Manipulating temperature in horticulture

• Frost protection
• Wind machines, sprinklers, heaters
• Ice layer insulates
• Liquid to solid (ice) transition produces heat

35
Manipulating temperature in horticulture

• Refrigerated storage of fruits, vegetables, cut
  flowers
• Slows down metabolism, extends post-harvest shelf
  life
• Not suitable for all horticultural crops

36
Summary

• Climatic conditions can vary at several different
  scales
• Variation is due to factors such as large water
  bodies, topography, altitude, etc.
• Responding to micro- and macro-climates is
  important for horticulturists and temperature
  influences selection of plants
• Many techniques are used to modulate temperature
  for production of horticultural crops