Yaqiu Li
Jiangfeng Wei
Yan Zhang
Wenyan Yu

 Land-use emissions
 Rice and methane
 Climate change effects on rice

Land use
“The total of arrangements, activities, and inputs that people undertake in a certain land cover type.”
 Peri-Urban Land
 Wetlands
 Cropland
 Agroforestry Land
 Rangeland/Grasslands
 Forest Land
 Deserts
In sequence of increasing intensity of use, basically

The Influence of Land Use on Greenhouse
Gas Sources and Sinks
 Land-use emissions
 Carbon stocks
 Land-Use Management

 CO
2 from net deforestation (nearly all)
 CH
4 from rice cultivation
 CH
4 from enteric fermentation of cattle
]
(53%)
 N
2
O from fertilizer application (80%)

Emissions of carbon dioxide due to changes in land use mainly come from the cutting down of forests

Source of
CH
4
CH
4
Source
Livestock
Rice paddies
Biomass burning
Natural wetlands
Mt CH4 yr -1
110 (85
–
130)
60 (20
–
100)
40 (20
–
80)
115 (55
–
150)
Gt C-eq yr -1
0.6 (0.5
–
0.7)
0.3 (0.1
–
0.6)
0.2 (0.1
–
0.5)
0.7 (0.3
–
0.9)

N
2
O Source
N
2
O Source
Cultivated soils
Biomass burning
Livestock (cattle and feed lots)
Natural tropical soils — wet forests
Natural tropical soils — dry savannas
Natural temperate soils — forests
Natural temperate soils
— grasslands
Mt N
2
O yr -1
3.5 (1.8
– 5.3)
0.5 (0.2
– 1)
0.4 (0.2
– 0.5)
3 (2.2
– 3.7)
1 (0.5
– 2)
1 (0.1
– 2)
1 (0.5
–
2)
Gt C-eq yr -1
0.9 (0.5
– 1.4)
0.1 (0.05
– 0.3)
0.1 (0.05
– 0.13)
0.8 (0.6
– 1)
0.3 (0.1
– 0.5)
0.3 (0.03
– 0.5)
0.3 (0.1
–
0.5)

 Land-use change is often associated with a change in carbon stocks.
 conversion of natural ecosystems to permanent croplands,
 conversion of natural ecosystems for shifting of cultivation,
 conversion of natural ecosystems to pasture
 abandonment of croplands,
 abandonment of pastures,
 harvest of timber,
 establishment of tree plantations

Global carbon stocks in vegetation and top 1 m of soils
Area
(10 6 km 2 )
Carbon Stocks (Gt C)
Biome Vegetation Soils Total
Tropical forests
Temperate forests
Boreal forests
Tropical savannas
Temperate grasslands
Deserts and semideserts
Tundra
Wetlands
Croplands
Total
17.6
10.4
13.7
22.5
12.5
45.5
9.5
3.5
16.0
151.2
212
59
88
66
9
8
6
15
3
466
216
100
471
264
295
191
121
225
128
428
159
559
330
304
199
127
240
131
2011 2477

 Vegetation can “sequester” or remove carbon dioxide from the atmosphere and store it for potentially long periods in above- and belowground biomass, as well as in soils.
 Soils, trees, crops, and other plants may make significant contributions to reducing net greenhouse gas emissions by serving as carbon
“sinks.”


Avoid emissions through the conservation of existing carbon stocks in forests and otherecosystems, including in soils (i.e., reducing LULUCF emissions). An example is reducing the rate of deforestation.
 Sequester additional carbon in forests and other ecosystems (including in soils), in forest products, and in landfills (i.e., enhancing LULUCF removals). An example is planting trees where there have not been trees in the past (afforestation).

 Substitute renewable biomass fuels for fossil fuels (i.e., fuel substitution), or use biomass products to replace products from other materials such as steel or concrete, that have different, often greater, fossil-fuel requirements in their production and use (i.e., materials substitution).

Mean annual carbon emissions from alternative land-use management options (1991-2001).

 1. Methane (CH4) is second important greenhouse gas (GHG).
 2. In 100 year period, a molecular CH4 can absorb about 25 times more energy than a molecular CO2.

Methane emission from rice fields

Global estimates of CH4 emission from rice fields
 1. The source strength of rice fields in Asia was estimated to range between
46 and 63 million t/yr of methane.
 2. Comprising 51% of the global harvested rice area, rice fields in China and India emit 29-40 million t/yr.
 3. Global estimates of rice field methane production range up to 100 million t/yr.

 Irrigated rice, comprised 50% of total rice area, accounts for 80% of methane emissions.

 1. Troposphere & stratosphere :
 2. Soil: about 30 Tg/yr
 broken down by OH
 Troposphere: 506 Tg/yr
 Stratosphere: 40 Tg/Yr

 Emission reductions produce an immediate and significant impact on climate change
 Why?

Rice Paddies and methyl halides

Figure 1.
Maxwell, California, averaged weekly fluxes during 1998 for methane, methyl chloride, methyl bromide, and methyl iodide. Arrows indicate maximum tillering (M,
55 DAS), booting (B, 70 DAS), heading (H, 80 DAS), flowering (F, 90 DAS), and the reflooding date (RF, 45 DAS). The flux for all gases is shown; note differing scales of emission for each gas. Symbols: , straw-incorporated plots; , burnt straw plots; , controls.
Error bars show one standard deviation.

 Fig. 2.
Maxwell, California, averaged weekly fluxes during 1999 for methane, methyl chloride, methyl bromide, and methyl iodide. Arrows indicate maximum tillering (M,
47 DAS), booting (B, 75 DAS), heading (H, 89 DAS), and flowering (F, 97 DAS). The flux for all gases is shown; note differing scales of emission for each gas. Symbols: , strawincorporated plots; , burnt straw plots; , controls. Error bars show one standard deviation

The worldwide rice farming contributes methyl bromide -----1% methyl iodide -------5%

----What the rice paddies looks like from the sky?
----People working in the rice paddies.

 One of the world’s most important food crops, staple food for over 50 % people in this world.
 To meet the demands of a growing population, agricultural productivity must continue to increase.
 If global climate changes act to reduce food production, serious, longterm food shortages and aggravation of societal problems could result.

1. Greenhouse Gases and Increased temperature:
Concentrations of GHGs like CO2 and CH4 have increased significantly since preindustrial times. The concentrations of these gases have a powerful influence on the average global temperature of the planet, and consequently, on the global climate.

2. Stratospheric Ozone Depletion Effects on Rice---UV-B Radiation:
.
Rice is the world’s most important food crop and grown mostly in tropical and subtropical countries.
. It is know that UV-B radiation is highest in tropical regions where rice is grown, because the stratospheric ozone layer is high latitude, and the solar angles are higher.
. After preindustrial period, people have release great amount of ozone decomposing matters, like chorofluorocarbons (CFCs) which already induced stratospheric ozone depletion, thus increasing the incoming UV-B.

Biodiversity Yield
Biogeochem
Circling
Endpoints
Competition pest, Pathogen, Decomposition
Ecosystem
Growth,Yield Morphology,
Chemical matters
Photosynthesis
Carbon Allocation
Targets
UV-B
Whole Plant
Tissue
Molecular known less known

Effect of UV-B on Rice Yield
Cultivar ‘ Lebonnet ’
16
Seed dry weight (g) 14
12
10
8
6
4
2
0
0 16 23 32
Percent UV-B Enhancement
1.Possible trends towards a reduction in seed yield under enhanced
UV-B conditions of ozone depletions of 8 to 16%
(Florida, US, 1984)

2. Rice growth and photosynthesis can be suppressed by exposure to UV-B under greenhouse conditions.
3. UV-B can induce the accumulation of UV-absorbing pigments and alter leaf surface characteristics.
But, it is unknown whether these responses are sufficient to completely protect rice from increased exposure to UV-B.
4. UV-B can alter plant morphology without reducing plant biomass. These morphological traits, like tillering, is known to influence rice yield, UV-B could potentially alter grain yield without apparent reductions in total production

5. UV-B radiation changing rice productivity related to radiation magnitude and direction. And this character depends on rice cultivar.
6. Results from pilot experiments indicate that UV-B enhancement can significantly increase the susceptibility of rice to blast disease.
7. UV-B enhancement is known to alter the competitive balance between crops and weeds

Effects of CO2 and temperature on rice production

Effects of CO2 and temperature on the rice ecosystem
 Increasing atmospheric CO2 stimulates plant growth, the beneficial effects on rice growth have been observed for levels only up to 500 ppm.
Some plant species respond positively to CO2 levels up to
1,000 ppm.
 The benefits of increased CO2 would be lost if temperatures also rise. That is because increased temperature shortens the period over which rice grows.

Interactive effects of CO2 and temperature
8000
7000
6000
5000
4000
3000
2000
1000
0
0
1
2
3
Temperature change (K)
4
5
330
450
570
CO
2
(ppm)
(Bachelet et al., 1993)

Indirect effects of global climate change on rice
 Altered timing and magnitude of precipitation can induce drought or flood injury
 Increased temperatures, and/or changes in precipitation could have dramatic impacts on rice diseases and insects.
 Enhanced UV-B, enriched CO2 and increased temperatures may all alter competition between rice and major weeds, and the contribution of other organisms to nitrogen fixation in rice fields.

Both models ( ORYZA1 , SIMRIW ) were potential production models – i.e. yield determined only by temperature, sunlight, CO2 level, daylength, crop variety, planting and harvest dates
Did not take into account: water limitations nutrient (N,P,K) limitations weeds, pests & diseases

General Circulation Models (GCMs)
Name
Base CO 2 (ppm)
Temperature change ( C)
Precipitation change (%)
GFDL GISS UKMO
Geophysical
Fluid
Dynamics
Laboratory
Goddard
Institute of
Space Studies
United
Kingdom
Meteorological
Office
300
+4.0
300
+4.2
323
+5.2
8 11 15

GFDL
3 GCM scenarios
68 weather stations
(Matthews et al., 1995)
% change in regional rice production predicted by ORYZA1 and SIMRIW under different GCM scenarios
ORYZA1
GFDL
+6.5
GISS
-4.4
UKMO
-5.6
SIMRIW +4.2
-10.4
-12.8

 The results of recent international modeling exercises suggest a mixed future of 2XCO2 for rice production in Asia, with some countries benefiting and others losing production.
 Overall, Asian rice production, based on present varieties and systems, could decline by about 4% in the climates of the next century.

ENSO and rice production ( Sri Lanka)
October to May
May to September

 Adjusting planting dates to avoid higher temperatures at flowering time (warmer regions)
 Breeding temperature tolerant varieties (warmer regions)
 Transition from single-cropping to double-cropping where extended growing season permits (cooler regions)
 Selection for varieties with greater response to elevated
CO2 (all regions)
 Breed crop plants tolerant to UV-
B radiation

 Land use change has an influence on green house gas sources and sinks.
 Rice paddies are a large source of CH4, an assessment of the agricultural effects of global environmental change must include rice as a crop of primary interest.
 While there is some information regarding the single effects of UV-B, CO2, temperature and precipitation on rice, little is know about the interactive effects of these factors.