Transcript Baldocchi Food Ag Board 2007

Global Change and Agriculture:
The Effects that Plants Have on Climate, and Vice Versa
Dennis Baldocchi
Professor of Biometeorology
Department of Environmental Science, Policy and
Management
College of Natural Resources
State Board of Food and Agriculture
July 25, 2007
Topics Covered
• Trends in Temperature
– Implications on Winter Chill/Dormancy
• Trends in Phenology
– +/- of Increasing Growing Season Length
• Trends in Water Use
– Pan ET and ‘Solar Dimming’
– Combined effects of Elevated CO2 and Temperature
• Trends in Land Use Change
– Evaporative Cooling and Albedo change
Summary
•
Climate Change is in Motion in California
–
•
There is a trend in reduced winter chill and winter dormancy
–
–
–
•
Increase vulnerability of fruit trees to late frost
May increase carbon sequestration, if water is plentiful, and increase water use
may cause a miss-match between flowering and pollinators
Water consumption will increase in the future
–
–
•
Leads to a reduction in fruit and nut production
The future trends may not be linear, but could accelerate if winter fog patterns change
Breeding programs are needed to produce cultivars that require less winter chill
Spring phenology is advancing
–
–
–
•
CA is warming, but interannual variation in rainfall is greater than predicted trends in the near
term
Potential water ‘savings’ by elevated CO2 are offset by warmer temperatures
CA is not be experiencing water savings due to ‘solar dimming’.
Land use change from Natural to Agricultural Landscapes has altered the surface
energy balance
–
–
Crops are Darker than grasslands and absorb more energy
But Evaporative cooling reduces air temperature, in comparison
Temperature and Agriculture
• Length of Growing Season
• Length of Dormant Season
• Extreme Cold
– Fruit, flower, and/or pollination damage
• Extreme heat
– Fruit damage
– Leaf damage
Temperature Trends, Selected Sites
Camp Pardee, CA
Foothill Rangeland
Antioch, CA
Sac-San Joaquin Delta
19
18.0
17.5
17.0
17
16.5
Tair(C)
Mean temperature (oC)
18
16.0
16
15.5
15
15.0
14.5
1940
1950
1960
1970
1980
1990
2000
2010
14
1950
1960
1970
1980
Year
Warming Rate: ~ 1.5 C ++ per 50 Years
1990
2000
2010
Estimating Winter Chill
 chillhours  d  2  (T
ref

Tref  Tmin
2
Tmax
)
Noon
a
Tave
b
d
Tref

c
Tmin
d
chillhours
 tan   (Tref  Tmin )
2
tan  
a
6hr

b Tave  Tmin
Downward Trend in Chill Hours near Brentwood, East Contra Costa
Chill Hours, below 7.22 oC Nov1 through Feb 29
Brentwood, CA
1600
1400
1200
20 year record,
CIMIS Data
1000
800
600
400
1985
1990
1995
2000
2005
2010
2000
2005
2010
Chill Degree-Hours, below 7.22 oC Nov1 through Feb 29
Year
4000
3500
3000
2500
2000
1500
1000
1985
1990
1995
Year
Reductions in Winter Chill are being Experienced across
the State and they are expected to Continue into the Future
Trends in Winter Chill Degree Hours Accumulation (degree-hours per year)
Nov-Mar, 0 to 7.22 C
1600
Red Bluff, CA, B1
Chill Hours, below 7.22 oC
1400
42
41
1200
1000
800
600
400
40
200
1940
1960
1980
2000
2020
2040
2060
2080
2100
2120
Years
1800
39
Chill Hours, below 7.22 oC
1600
38
37
Davis, CA, B1
1400
1200
1000
800
600
400
200
0
1940
36
1960
1980
2000
2020
2040
2060
2080
2100
2120
Years
1600
-100 to -75
-75 to -50
-50 to -25
-25 to -10
-10 to 0
0 to 10
34
Fresno, CA, B1
1400
Chill Hours, below 7.22 oC
35
33
1200
1000
800
600
400
-124
-123
-122
-121
-120
-119
-118
-117
-116
-115
200
1940
1960
1980
2000
2020
2040
Years
Baldocchi and Wong, Climatic Change, in press
2060
2080
2100
2120
Photo © David Sanger
D. Lobell et al, 2006 Ag.Forest Met
Almond Yield (ton acre-1)
Almond Yield
Decreases with
Warmer and Wetter
winters
Almond Yield Anomaly
So What?:
Phenology: The Timing of Plant Activities
Flowering
Leaf-out
Spring is Advancing by about 3 days per Decade across
the Northern Hemisphere
Schwartz et al. 2006 Global Change Biology
Estimated Trends in Phenology in CA Rangeland
Estimate of onset of photosynthesis for blue oak woodland
98
Coefficients:
b[0] 303.01
b[1] -0.108
r ² 0.331
96
Day NEE = 0
94
92
90
88
86
84
82
1940
1950
1960
1970
1980
Year
1990
2000
2010
Length of Growing Season, Carbon and Water Exchange
Deciduous Forests
Michigan, USA
Massachusetts, USA
Prince Albert, CANADA
Indiana, USA
Tennessee, USA
Denmark
Belgium
Ontario
Italy
Annual Grassland, CA
Japan
100
Broad-Leaved Forests
0
NEE (gC m-2 yr-1)
-100
-200
-300
-400
-500
-600
-700
-800
100
150
200
250
Length of Growing Season
Ryu, Baldocchi and Ma, unpublished
Baldocchi et al, 2001 Bull. Am. Meteorol. Soc.
Water and Agriculture
Camp Pardee
30
1200
25
1000
annual Precip (mm)
rainfall (inches per year)
Antioch, CA
20
15
10
5
mean: 548.6446
stddev: 196.2281
800
600
400
200
0
1950
1960
1970
1980
Year
1990
2000
2010
0
1940
1950
1960
1970
1980
1990
2000
2010
Year
•Year to Year Variability Exceeds any Existing or Expected Future Trends
•Snowpack and the Timing of its Melting will be Affected
Evaporation, Water Availability and Climate Change
• Global Warming Should:
– Accelerates the Water Cycle by increasing
saturation vapor pressure
– Increase Evaporation
• But Negative Feedbacks include:
– Increase Humidity and Cloud Cover
– Decrease Solar Radiation, ‘Solar Dimming’
– Widespread Reduction in Pan or Potential
Evaporation
Pan ET in China
Literature is showing a
long term trend with a
decrease in pan
evaporation:
Could there be Water
Savings for Irrigated
Agriculture in CA?
Liu et al. Journal Geophysical Research, 2004
Solar Radiation in China
Trends in Pan Evaporation in CA:
Irrigated Central Valley
Semi-Arid Rangeland
Davis, CA
110
Camp Pardee
68
100
64
Pan ET (in y-1)
62
80
70
60
58
56
54
60
52
50
1940
50
1950
1960
1970
1980
1990
2000
2010
48
1945
Year
1950
1955
1960
1965
1970
1975
1980
Time
Antioch, CA
78
76
74
Pan ET (in y-1)
-1
Pan ET (in year )
66
90
72
70
68
66
64
62
60
1955
1960
1965
1970
Time
1975
1980
Hildalgo et al. 2005 J Hydromet:
‘Trends for PET are unclear in CA’
•Feedback Loops Break in Water-Limited Regions
Ea/Epot
Water limited
Energy limited
Q/Epot
1
Ea/Epot
0
0
1
P/Epot
Farquhar and Roderick, Pontifical Academy of Science, in press
Lessons from Direct Evaporation Measurements over California
Rangeland
•CA Ecosystem are Water, not Radiation Limited
•Savanna Uses More Water than Grassland
-Savanna Soil holds about 78 mm more Water
•Annual ET Decreases with Solar Radiation
-Rg decreases as Clouds and Rain increase
-Range in ET is 100 mm/yr
Savanna Woodland and Annual Grassland
440
420
400
ET (mm y-1)
380
360
340
320
300
280
260
240
17.4
17.6
17.8
18.0
-2
-1
<Rg> (MJ m d )
Ryu, Ma and Baldocchi, unpublished
18.2
18.4
Elevated CO2, Facts and Myths
•
Enhances Photosynthesis
– Down-Regulation in Ps from
Nutrient Limitations
•
Reduces Stomatal Closure
– Direct Effect
• Reduces Transpiration and
Increases WUE
– InDirect Effect and Positive
Feedback
• Elevated Leaf Temperature,
augments Transpiration
•
Greater Growth and Leaf Area
– Bigger plants grow faster. +
– Bigger plants transpire more
– Soil moisture pool depleted
faster: -
•
Herbivore Interactions
– Insects eat more foliage to
compensate for lower N quality of
leaves
Projected Water Use in a Walnut Orchard
will increase by ~145 mm (6 in) with T+3 C
and CO2 at 500 ppm
Walnuts
2003 Climate data
250
ET: 1054 mm
Ta + 3C, CO2 =500 ppm
ET: 1199 mm
40
LE (W m )
150
-2
-2
LE (W m )
200
100
20
0
50
-20
0
0
50
100
150
200
Day
250
300
350
400
0
50
100
150
200
Day
250
300
350
400
Agriculture and Land use Change
•
Albedo
– Crops are darker than dead grass,
so the Absorb more solar energy
•
Evaporation Ratio, E/Rn
– Crops do not suffer for soil
moisture deficits and are fertilized
– They achieve a larger Leaf Area
Index and possess lower Surface
Resistance than annual grasses
or savanna woodlands
– Crops experience greater rates of
ET and have depressed Surface
Temperatures, compared to native
vegetation
1.75
Carbon Uptake
– Crops are actively assimilating
carbon dioxide during the summer
wheat
corn
jack pine
oak-savanna
1.50
1.25
E/Eeq
•
2.00
1.00
0.75
0.50
0.25
0.00
10
100
1000
Rcanopy (s m-1)
10000
Difference in Tmax:
Natural vs managed land
Land Use Change and Climate
Change in the Central Valley
•Large Scale Irrigation reduces
Temperature compared to natural
vegetation
Kueppers et al, 2007, Geophysical Res. Letters
•But Increases Nighttime
Temperatures through humidification
of the air and increasing downward
longwave energy
•Rate of Climate Warming in CA is
dampened due to Land Cse Change
-negative feedbacks by
evaporative cooling outpace
positive effects of lower albedo
Christy et al, 2004, J Climate
Some Potential Solutions
• Changes in crops, timing and rotation
– Don’t grow crops that are profligate water
users in the desert!
• Irrigation scheduling and soil moisture
management
• Mulches and increased soil organic matter
to reduce soil evaporation and runoff
• Precision agriculture and drip irrigation
We are Linked to Past, We have a Responsibility to the Future
Palace of Minos at Knossos, ~2000 BC
•Climate Change is in Motion in California
•Long term production of valuable fruit crops is vulnerable
due to trends in reduced winter chill
•The future trends may not be linear, but could
accelerate if winter fog patterns change
•Breeding programs are needed to produce cultivars that
require less winter chill
•Water consumption will increase in the future
Extra Background Material
Temperature Anomaly Trends:
Instrument Record
Trends for Climate between Nov and Mar
Mote et al. 2005 BAMS
McKinney et al,
2006 AgForMet
Lobell et al 2006 AgForMet
Critical Temperatures and Yield
Lobell et al 2006 AgForMet
Phenology, a Measure of Global Change
Regression Coefficient of Phenological Event with Time, days per year
Menzel et al 2006 GCB; Menzel and Fabian, Nature, 1999
Trends, days per Decade
Feng and Hu, 2004, J Theor Appl Clim
Trends in Growing Season Length and Last Frost Dat
Feng and Hu, 2004, J Theor Appl Clim
United States
Christy et al 2006 J Climate
Trends in Dry and Wet Spells
Feng and Hu, 2004, J Theor Appl Clim
United States
Coupled Energy Balance-PBL Model
D. Baldocchi, unpublished
Does Global Dimming affect ET?
6.1
6.0
ET (mm d-1)
5.9
5.8
5.7
b[0] -0.882
b[1] 0.216 mm (MJ m-2)-1
r ² 0.999
5.6
5.5
5.4
5.3
28.5
29.0
29.5
30.0
30.5
31.0
Rg (MJ m-2 d-1)
31.5
32.0
32.5
Global Irrigation Intensity
Kueppers et al, 2007; Siebert et al., 2005
Christy et al., 2006 J Climate
Issues to Consider Regarding Role of C
Sequestration to Mitigate Climate Change
• Vegetation operates less than ½ of the year and is a solar collector
with less than 2% efficiency
– Solar panels work 365 days per year and have an efficiency of 20%+
• Ecological Scaling Laws are associated with Planting Trees
– Mass scales with the -4/3 power of tree density
• Available Land and Water
– Best Land is Vegetated and New Land needs to take up More Carbon
than current land
– You need more than 500 mm of rain per year to grow Trees
• The ability of Forests to sequester Carbon declines with stand age
• There are Energetics and Environmental Costs to soil, water, air and
land use change
– Changes in Albedo and surface energy fluxes
– Emission of volatile organic carbon compounds, ozone precursors
– Changes in Watershed Runoff and Soil Erosion
• Societal/Ethical Costs and Issues
– Land for Food vs for Carbon and Energy
– Energy is needed to produce, transport and transform biomass into
energy