1. Climate Change
Carbon Sequestration
Links between CO2 and climate change were forecast
•
more than 100 years ago (Arrhenius).
Given little attention because of several uncertainties,
•
especially instrumented measurements of
atmospheric CO2.
Scientists thought the oceans would simply absorb
•
any excess CO2.
Measurements have since eliminated that
•
uncertainty.
Soil 7170 Pre-class Review Notes
2. Atmospheric CO2 concentration (ppmv) 380
370
360
350
340
330
320
310
1958 1962 1966 1970 1974 1978 1982 1986 1990 1994 1998 2002
Monthly atmospheric CO2 concentration as monitored at the Mauna Loa
Observatory (Data from http://cdiac.esd.ornl.gov/)
5. Climate Change
Carbon Sequestration
• Carbon in SOM is recognized as a means to mitigate the
increase in atmospheric CO2 that has been caused by burning
fossil fuel
• Plants utilize CO2 and H2O to produce carbohydrates, the
basic organic building block, which converts atmospheric
CO2 into an organic form
• When the plants die, the organic material remains in organic
form until the soil micro-organisms use them for energy,
during the decomposition, CO2 is released back into the
atmosphere
• By increasing the level of soil organic matter, we keep or
“sequester” carbon in organic form which reduces the
amount of CO2 in the atmosphere
Soil 7170 Pre-class Review Notes
6. Notes
Carbon storage values in the boreal region reach a maximum of 1,250 metric tons of carbon per hectare. Carbon
storage values greater than 1,000 metric tons of carbon per hectare account for 2 percent of the area falling in
the greater than 300 metric tons per hectare class. Carbon storage values are not shown for Greenland and
Antarctica, where limited data were available.
Sources:
1. Food and Agriculture Organization of the United Nations (FAO). 1995, Digital Soil Map of the World (DSMW)
and Derived Soil Properties. Version 3.5. CD-ROM.
2. Batjes, N.H.. 1996. quot;Total Carbon and Nitrogen in the Soils of the Worldquot;. European Journal of Soil Science
47:
Available On-line at: Source Link.
7. Units are in Gigatonnes
(GT) or billions of tonnes
CO2 and the carbon cycle (Schimel et al. 1995)
8. Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric
Administration. [Online] http://www.pmel.noaa.gov/co2/gcc.html Accessed: 25 Nov 2005
9. Climate Change
Carbon Sequestration
• Farmers can receive payment for implementing specific
practices to increase soil organic matter
• The increase in soil organic C is meant to offset the
release of CO2 by industry
• Industry is paying for a “carbon credit”
• If the land is tilled, the soil organic carbon can be quickly
released by to the atmosphere as CO2
• This is not a permanent solution to solve increasing
atmospheric CO2 because C storage capacity of soil is
limited
Soil 7170 Pre-class Review Notes
10. Climate Change
Potential Climate Change
Impacts on Agriculture
As weather patterns change over time in western
•
Canada, we will need to continue to adapt our crop
choices and practices.
The impacts of climate change on agriculture will be
•
reflected through the response of crops, livestock,
soils, weeds, insects and diseases to the elements of
climate to which they are most sensitive
Can we anticipate the response of various crops to
•
these changes so that we can improve our crop
outcomes in the future?
Soil 7170 Pre-class Review Notes
11. Climate Change
Potential Climate Change
Impacts on Agriculture
• How will future weather affect the yield and quality
of western Canadian crops?
• Effects on individual plant organs
• Effects on plants
• Effects on field
• Indirect Effects
• Weeds
• Pathogens
• Insects
• Soil temperature
Soil 7170 Pre-class Review Notes
12. Climate Change
Potential Climate Change
Impacts on Agriculture
Plant Processes Affected by the Environment
•
• Photosynthesis
• Respiration
• Partitioning
• Development rate
Soil 7170 Pre-class Review Notes
14. Wheat yield versus atmospheric CO2. Amthor, 2001, as reported in Pritchard
and Amthor 2005 Crops and environmental change. Food Products Press
15. Photosynthesis and Elevated
CO2
• Increased biomass production
• C3 > C4
• Enhanced biomass production
more apparent in dry
conditions, especially for C4
crops
Samarakoon and Gifford, 1995.
J Biogeog. 22: 193.
16. • Yield and Elevated CO2
• % increase in yield of 9
soybean varieties grown in
CO2-enriched air compared
to ambient air.
Ziska et al, 2001, as reported
in Pritchard and Amthor 2005
Crops and environmental
change. Food Products Press
17. • Photosynthesis and
Elevated CO2
• When exposed for long
periods to high CO2, the
increased biomass
response is reduced
(individual leaves)
• “acclimation”
Bunce, 1995. J
Biogeog. 22: 341.
18. • Photosynthesis and
Elevated Temp
• The optimum temperature
for photosynthesis is
generally higher for C4
plants.
Adapted from Stone, 2001,
as reported in Pritchard
and Amthor 2005 Crops
and environmental
change. Food Products
Press
19. • Elevated Temp
and CO2
• Winter wheat biomass
production declines
with rising temp for
either ambient or
elevated CO2
Batts et al. 1998. J.
Agric. Sci. 130: 17-27.
20. Climate Change
Potential Climate Change
Impacts on Agriculture
Respiration and Elevated CO2
• It is unclear if respiration is directly affected by
atmospheric CO2 levels
• If plants respond to increased CO2 by producing
more biomass, then the plant will increase the
amount of growth respiration
Soil 7170 Pre-class Review Notes
21. Climate Change
Potential Climate Change
Impacts on Agriculture
Partitioning and Elevated CO2
• Most plants grown under elevated CO2 have
greater root/shoot ratios, especially in nitrogen-
limited conditions.
• The tendency is for harvest index to increase
with elevated CO2.
Soil 7170 Pre-class Review Notes
22. % change in root/shoot ratio for crops in CO2-enriched atmosphere (264
observations). Data from Rogers et al, 1996 as reported in Pritchard and Amthor 2005
Crops and environmental change. Food Products Press
23. Climate Change
Potential Climate Change
Impacts on Agriculture
Partitioning and Elevated Temperature
• Warmer temperatures can spur photosynthesis rates
and production of assimilates which takes place in
the leaves
• Since the shoots are closer to the source of
assimilates than the roots, this will advantage the
shoot tissue
Soil 7170 Pre-class Review Notes
24. Temp & CO2 Effects on Root Partitioning
Root biomass (% of
10
total plant biomass)
Root Biomass (% of total plant biomass)
increases with
8
increasing CO2 but
decreases with 6
increasing air
temperature. 4
2
Data from Batts et al,
1998. J. Agr. Sci. 130:
0
17-27.
Warm Average Cool Normal Elevated
Temperature CO2
25. Climate Change
Potential Climate Change
Impacts on Agriculture
Mineral Nutrition and Elevated CO2
• Elevated CO2 improves growth and yield but
decreases nutrient concentrations as plants are unable
to acquire enough nutrients to keep pace with more C
from higher photosynthesis
• However, soil warming generally increases nutrient
uptake capacity of plant roots and may mitigate the
dilution impact of high CO2 to some extent
Soil 7170 Pre-class Review Notes
26. Barley Grown at Different Root Zone Temperature
3 b
b
b
b
a
a
2
5C
10 C
15 C
1
0
Water Use Water Use Efficiency
(Liters) (grams per liter)
Root growth responds positively to increased soil temperature within the range
experienced in western Canada. Data from Sharratt, 1991, Agron. J. 83: 237-239.
27. Climate Change
Potential Climate Change
Impacts on Agriculture
Bunce, 1995. J Biogeog. 22: 341-347.
Eastern USA field trial
• No yield increase at increased CO2 levels in the
field for alfalfa and orchard grass even though CO2
assimilation rates of individual leaves were higher
(only 2 reps)
• Leaf nitrogen content decreased in crops grown at
elevated CO2 level
• Weed yield was 2 to 4 times higher in both crops
with elevated CO2!!
Soil 7170 Pre-class Review Notes
29. Climate Change
Potential Climate Change
Impacts on Agriculture
Yield Components and Elevated Temperture
• Elevated temperature increases the growth rate but
decreases the time from flowering to maturity,
especially in determinate species
• Net effect of increased temperature is expected to
reduce individual grain size
Soil 7170 Pre-class Review Notes
30. Climate Change
Potential Climate Change
Impacts on Agriculture
Impacts on Pests
From
‘Agriculture and Climate
Change’
November 2005, National
Farmers Union
http://www.nfuonline.com
Soil 7170 Pre-class Review Notes
31. Climate Change
Potential Climate Change
Impacts on Agriculture
Effects of Elevated CO2
• Increased biomass in C3 plants (although perhaps
not as much as first suggested)
• Increased WUE in most plants
• Increased root/shoot biomass ratio
• Decreased mineral content in the biomass
• Increased weed growth
Soil 7170 Pre-class Review Notes
32. Climate Change
Potential Climate Change
Impacts on Agriculture
Elevated Temperature
• Reduced biomass production
• Shift towards the optimum temperature for
photosynthesis in C4 plants
• Increased root growth and water (nutrient) uptake
• Reduced filling period and lower grain yields from
increased rate of maturity
• Increased pest pressure
Soil 7170 Pre-class Review Notes
33. Government of Canada, Climate Change Impacts and Adaptation Directorate. 2004.
Climate Change Impacts and Adaptation: A Canadian Perspective. [Online]
http://adaptation.nrcan.gc.ca/perspective_e.asp, last accessed 18 Sep 04
34. Climate Change
Potential Climate Change
Impacts on Agriculture
Feedbacks
Example 1: Higher WUE-higher plant productivity
•
Will the lower amount of water needed to
produce each unit of biomass be offset by larger
plants with bigger leaves such that plant water
use does not change or perhaps even increases?
Example 2: Higher WUE and lower ET
•
Higher WUE will reduce ET, decrease latent heat
and increase sensible heat (i.e. warmer
temperatures in the canopy). Will the warmer
temperature cause higher evaporative demand?
Soil 7170 Pre-class Review Notes
35. Climate Change
Potential Climate Change
Impacts on Agriculture
Western Canada
Longer growing season will facilitate northward
•
expansion of agriculture (which may be limited by
lack of suitable soil)
Potential increased variety of crops suitable for
•
production
Warmer temperatures will hasten crop maturity,
•
potentially reduce yields
Soil 7170 Pre-class Review Notes
36. Climate Change
Potential Climate Change
Impacts on Agriculture
Western Canada
For perennial grasses and forages, which maintain
•
an actively growing ground cover through the entire
growing season, an increase in temperature will
increase potential evapotranspiration
Unless there is a corresponding increase in
•
precipitation, perennial crops may also suffer yield
declines.
Soil 7170 Pre-class Review Notes
37. Climate Change
Potential Climate Change
Impacts on Agriculture
Western Canada
• Increased temperatures may facilitate the expansion
of warm-season weed species to more northerly
latitudes
• Insect pests, fungal and bacterial pathogens of
importance to agricultural production are sensitive
to climate change through the direct effects of
changes of temperature and moisture on the pest or
pathogen, on host susceptibility and on the host-
parasite inter-relation.
Soil 7170 Pre-class Review Notes
