Grassland management and soil C sequestration: current research in the United States

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Grassland management and soil C sequestration
current research in the United States
Richard T. Conant Natural Resource Ecology
Laboratory Colorado State University Fort
Collins, CO
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Changes in C cycling with improved pasture
management
CO2
Improved management (fertilization, grazing, etc.)
Initial
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Potential regional to global C sequestration in
grasslands
460
69.8
71.5
45.5
8.0
2.5
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Land use/management options for C sequestration
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Grasslands of North America
Mixed prairie
Fescue prairie
Palouse prairie
Tallgrass prairie
Short-grass steppe
California prairie
Coastal prairie
Desert grassland
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Arid/semiarid grasslands of North America
Desert grassland (Jornada LTER)
Short-grass steppe
Palouse prairie (E. WA state)
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Semiarid/mesic grasslands of North America
Mid-grass prairie (near Ottawa, KS)
Tall-grass prairie (Konza LTER)
Coastal prairie
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Land use in Virginia, USA
AVHRR data (1km res.)
MRLC data (30 m res.)
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Southeastern Pasture land by MLRA
pasture land
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Mesic grasslands of North America
Virginia, USA
Mississippi, USA
Tennessee, USA
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Agro/pastoral ecosystems Research at NREL
Regional analysis Integrated assessment
Projections
Integrator
Agroecological Model NSF, USDA, DOE
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Grassland/soil C research in the US
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Intensive rotational grazing Effects on biomass,
NPP
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VA Farm locations

• Soil Sampling
• Sample locations
• Sampling scheme

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(No Transcript)
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Soil Organic C (50cm)
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Conclusions

• Intensive grazing management can increase soil C
• Average 3 Mg C ha
• Root biomass and C are lower under IG
• On average, 50 of C sequestered is at 0-10cm
• POM C increased for three of four sites
• Excluding Grayson county, POM directly related to
• C sequestration

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Lit. review of impacts of improved pasture
management on soil C

• Requirements of papers included
• Management is main influence on soil C
• Paired plot with management control or measured
  changes over time
• Soil C (wet oxidation, dry oxidation, LOI)
• Conversion from cultivation to grassland
• Literature survey
• 112 references
• 308 data points
• 18 countries (see map)
• Evaluated influence of
• Management (meta-analysis)
• Climate (MAT, MAP, PET)
• Depth
• Time
• Native vegetation

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Soil C response to grassland management

• Soil C increased for 74 of all data points
• Average increase 40.6
• Average Decrease12

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Soil C response to grassland management
N8
N6
N79
N11
N119
N3
N47
N37
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Soil C sequestration with changes in grassland
management
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Conclusions

• Historical land use change
• substantial in all nine states
• 0.22 MMtC yr-1
• Current pasture management
• fertilization gt legumes, except in TN
• fertilization 1.00 MMtC yr-1
• sowing legumes 0.75 MMtC yr-1
• Potential future land use through 2010
• Land use change 9.0 MMtC
• fertilization 12.6 MMtC
• sowing legumes 9.4 MMtC

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Site-level investigation of grassland
management/soil C
Monitoring sites EPA, DOE, USDA
Auditing
Agroecological Model NSF, USDA, DOE
Site Networks EPA, DOE
Field Experiments NSF, USDA
Model Param.
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National Databases

• Survey data
• Natural Resources Inventory
• Land use
• Crop rotations
• Pasture management
• STATSGO state level soil data
• SSURGO county level soil data
• soil properties
• PRISM
• Long-term climate data
• all weather stations
• Digital Elevations Models
• 30m resolution

• Remotely sensed data
• Multi Resolution Land Characterization (30m)
• Advanced Very High Resolution Radiometer (1km)
• Moderate Resolution Imaging Spectrometer
• NPP
• LAI
• NDVI
• 8-day composites
• 1km/250m resolution

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National Resources Inventory Database for IPCC
Natl Inventory
NPM
102B
4 Urban
67 Cropland
9 Pasture
9 Range
1 Forest
10 Misc.
4 Oth
2 LFS
24 L
18 SIL
8 CL
40 SICL
2 SIC
2 FSL
Improved pasture
Unimproved pasture
Improved pasture
Unimproved pasture
MLRA 102B lies at the western edge of the corn
belt. Average annual precipitation is 500 - 650
mm. Average annual temperature ranges from 9 -
11 degrees C.
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Regional/local Databases

• County Level Data
• Agricultural Statistics
• Pasture/range land area by county
• Fertilizer applied
• Dairy/beef cows
• PRISM
• Long-term climate data
• all weather stations

• Federal Land Data
• Forest service grazing allotments
• Grazing history
• Number of cattle
• Duration of grazing
• Not available electronically
• Bureau of Land Management data
• Rangeland health
• Grazing history
• Grazing allotments
• Not available electronically
• National parks/monuments
• No livestock grazing
• Animal density for select species

• State Level Data
• Some states have finer-scale soil surveys
• Soil properties
• erosion
• Land management
• State-owned land management
• Grazing history
• Irrigation history

• Research networks
• Long-term ecological research sites
• Ag. Res. Service Exp. Range sites
• University Experimental Ranges
• Federal/state managed sites
• NEON new NSF initiative

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Phase II
Phase I

• County-level information
• drainage (year)
• irrigation
• land capability class
• crop history
• conservation practices

• National databases for state-level information
• soils
• texture
• hydric soils
• depth
• soil series
• broad land use
• temperature
• precipitation
• native vegetation

Rural Appraisals submitted to conservation
districts
Land Use
Drainage
Soil Texture (STATSGO)
Land Cover (MRLC)
Irrigation
Conservation
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Current Southeastern pasture management
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C sequestration rates for sowing legumes and
fertilization
tC ha-1yr-1
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Current pasture land C sequestration
MMtC yr-1
Total for Southeastern US 2.35 MMtC yr-1
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Potential C sequestration in overgrazed grasslands
C sequestration potential (from literature)
Overgrazed area mask (from GLASOD)
Grassland mask (from DISCover)
C sequestration potential for overgrazed grassland
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Potential C sequestration in overgrazed grasslands
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Problems and shortcomings with existing grassland
databases

• Spatially aggregated
• - no from/to information
• - allows only gross rather than net estimates
• - incorrect assumptions can affect results
• - cant tie to spatial datasets (soil,
  climate, topography)
• Land omitted (public, non-forest, etc.)
• Expensive/time consuming
• - difficult to repeat frequently
• Little information on grassland management
• May be inconsistent
• - difficult to validate

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Detection of grazing management in grasslands
Can pastures under intensive rotational grazing
be distinguished from pastures that are managed
less-intensively using remote sensing?
Q1
Pastures under intensive rotational grazing are
(1) more productive (higher NPP) and (2) have
different seasonal distribution of aboveground
biomass and can, thus, be distinguished from from
extensively managed pastures remotely.
H1
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Intensive rotational grazing Effects on biomass,
NPP
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Intensive study sites pasture
 
 

• Pulaski, Virginia
• rotational grazing
• soil C root biomass (pasture project)
• clipping experiment
• LAI, clipping after rest period
• seasonal LAI, clipping, root biomass

• Spartansburg, Tennessee
• rotational grazing fertilization
• soil C root biomass (pasture project)
• clipping experiment (?)
• LAI, clipping after rest period

 
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Intensive rotational grazing changes in biomass
Time
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Intensive rotational grazing Effects of rest on
LAI
LAI (m2 m-2)
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Relationship between LAI and biomass (and biomass
C)
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Biomass (g C m-2)
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LAI
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Detection of grazing management in grasslands
Can rangeland under long-term grazing exclosure
and different grazing intensities be
distinguished using remote sensing?
Q2
Long-term grazing treatments of varying intensity
differentially affect LAI and can therefore be
identified using remote sensing.
H2
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Historical grazing in rangelands effects on NPP

• Changes in species composition (C4 shifts) in
  response to grazing
• should be manifest in seasonal distribution of
  NPP
• Seasonality of NPP is detectable using remote
  sensing
• Therefore, historical grazing intensity is
  amenable to remote sensing

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MODIS land cover products (moderate resolution
imaging spectrometer)

• NDVI
• LAI
• APAR
• Albedo
• Snow cover
• NPP

• Positives
• 250/1000m resolution
• 8 day intervals
• Standard format (HDF)
• Bands correspond with LANDSAT
• No charge!

• Negatives
• New instrument (no historic data)
• Problems w/ yr 1 data
• Standard format (HDF)

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Extensive sites

• Grazing exclosures/treatments
• Grazing history
• Neighboring ranches w/ grazing
• Species composition data
• National grasslands
• National wildlife refuges
• ARS Experimental ranges
• LTER sites
• National parks
• National/state historic sites

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US grassland C research current priorities
Regional analysis Integrated assessment
Projections
Integrator
Agroecological Model