Section 5 Climate Change slides

Soil 7170 Pre-class Review Notes

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.

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Atm

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Monthly atmospheric CO2 concentration as monitored at the Mauna Loa Observatory (Data from http://cdiac.esd.ornl.gov/)

Intergovernmental Panel on Climate Change, 2001. [Online] Available at http://www.ipcc.ch/pub/spm22-01.pdf Last accessed 1-Oct-2002.


Climate Change

• 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


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. "Total Carbon and Nitrogen in the Soils of the World". European Journal of Soil Science 47: Available On-line at: Source Link.

CO2 and the carbon cycle (Schimel et al. 1995)

Units are in Gigatonnes(GT) or billions of tonnes

Pacific Marine Environmental Laboratory, National Oceanic and Atmospheric Administration. [Online] http://www.pmel.noaa.gov/co2/gcc.html Accessed: 25 Nov 2005


Climate Change

• 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



Climate Change

Potential Climate ChangeImpacts 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?


Climate Change


• 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


Climate Change


• Plant Processes Affected by the Environment• Photosynthesis• Respiration• Partitioning• Development rate

Photosynthesis and Respiration. From Mathews et al. 2000 Biochemistry 3rd Edition, Addison-Wesley-Longman

Wheat yield versus atmospheric CO2. Amthor, 2001, as reported in Pritchard and Amthor 2005 Crops and environmental change. Food Products Press

Photosynthesis and Elevated CO2

• Increased biomass production• C3 > C4

• Enhanced biomass production more apparent in dry conditions, especially for C4crops

Samarakoon and Gifford, 1995. J Biogeog. 22: 193.

• 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

• 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.

• 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

• 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.


Climate Change

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



Climate Change

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.


% 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


Climate Change

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


Root biomass (% of total plant biomass) increases with increasing CO2 but decreases with increasing air temperature.

Data from Batts et al, 1998. J. Agr. Sci. 130: 17-27.

Temp & CO2 Effects on Root Partitioning

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Warm Average Cool Normal Elevated Temperature CO2


Climate Change

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


Root growth responds positively to increased soil temperature within the range experienced in western Canada. Data from Sharratt, 1991, Agron. J. 83: 237-239.

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Water Use (Liters)

Water Use Efficiency (grams per liter)

Barley Grown at Different Root Zone Temperature

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Climate Change

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 CO2assimilation 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!!


Bunce, 1995. J Biogeog. 22: 341.


Climate Change

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



Climate Change


Impacts on Pests

From‘Agriculture and Climate

Change’November 2005, National

Farmers Unionhttp://www.nfuonline.com


Climate Change


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


Climate Change


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

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


Climate Change


• Example 1: Higher WUE-higher plant productivityWill 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 ETHigher 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?

Feedbacks


Climate Change


• 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

Western Canada


Climate Change


• 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.

Western Canada


Climate Change


• 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.

Western Canada

Technology

Section 5 Climate Change slides