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Presented by Megan Lewis as part of the 2009 Place and Purpose Symposium run by the Landscape Science Cluster
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Towards image-based monitoring of soil erosion risk in southern Australia.
Megan Lewis
Place and Purpose Symposium 2009
Towards image-based monitoringof soil erosion risk in
South Australian agricultural lands
Assoc. Prof. Megan Lewis
Dr Ken Clarke
Dr Bertram Ostendorf
Landscape Futures ProgramThe University of Adelaide
Place and Purpose Symposium 2009
Overview
• Collaborative research program 2002-present
– University of Adelaide & Soil Conservation Council, Dept Water, Land & Biodiversity Conservation
• Approaches and key findings
• Collaborative process
• Ongoing research
Place and Purpose Symposium 2009
Context
• Cropping regions of SA
• Cereal cropping is integral to Australia’s economy
– ¼ of Australia’s cereal crops produced in SA: 5,382 kT
• Soil conservation essential for economically viability & sustainability
• Legislative requirement for soil conservation
– Soil Conservation & Land Care Act Act 1989
– Natural Resources Management Act 2004
• State Strategic Plan target
– 20% increase in land protected from erosion by 2014
• DWLBC monitors soil cover to minimise erosion
– Land Condition Monitoring Project (2000 – present)
Place and Purpose Symposium 2009
DWLBC Land condition monitoring project methodology
• Windscreen surveys along road transects, 5,500 locations
– 4 surveys / year
• Oblique visual estimate of:
– Cover
– Detachment
Place and Purpose Symposium 2009
DWLBC Land condition monitoring project methodology
• Regional and State-wide reports
Full cover
Bare
• Costly
• Limited to spatial and temporal samples, not spatially explicit
Place and Purpose Symposium 2009
What about remote sensing?
• Collaborative research with University of Adelaide & Dept. Water Land & Biodiversity Conservation 2002-present
• Aim: To bring benefits of remote sensing to SA Land Condition Monitoring Program
– Spatially explicit, comprehensive & objective assessment of cover
– Improved assessment of areas at risk/protected
– Increased temporal frequency
– Cost effective
• Funding: Soil Conservation Council, DWLBC, University of Adelaide, ARC Linkage grant
Place and Purpose Symposium 2009
Collaborative approach
Windscreen Survey data
Image indices
• Develop & test image indices
• Calibrate & validate with extensive existing WSS data
• Demonstrate relationships between field & image measures
• Enhance not replace field survey
• Develop organisational understanding & confidence in remote sensing approach
Operational use of remote sensing for land condition monitoring in SA
Place and Purpose Symposium 2009
Remote sensing approaches
• NOAA AVHRR
• AUSSIEGrass products
• MODIS
– Single date images
– Nadir BRDF adjusted reflectance 16 day composites
• Existing Indices
NDVI
PD54
• New index: UA Vegetation Index based on Cellulose Index
• Single dates
• Annual 16-day sequence
• 2001-present 16 day sequence
Place and Purpose Symposium 2009
Key technical findings
1. UA Vegetation Index best predictor of Cover Rating
– NDVI doesn’t discriminate bare soil from dry stubble
– PD54 difficult to calibrate over time, difficult for operational use
Place and Purpose Symposium 2009
University of Adelaide Vegetation Index
• Strongest relationships with Cover Rating
• UAVI = (Band 6 – Band 7) / (Band 6 + Band 7)
Clarke, K. and Lewis, M. (2009) Report 3: Development of a satellite image-based land condition monitoring system for South Australian agricultural regions. Land condition monitoring reports. Adelaide, The University of Adelaide.
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400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400
Wavelength (nm)
Re
fle
cta
nc
e
Blue Green Red Near infra-red Short wave infra-red
MODIS Bands 6 & 7
Soil
Dead
vegetation
Growing
vegetation
Place and Purpose Symposium 2009
Key technical findings
1. UA Vegetation Index best predictor of Cover Rating
– NDVI doesn’t discriminate bare soil from dry stubble
– PD54 difficult to calibrate over time, difficult for operational use
2. Relationships between image indices & Cover Rating from field survey
– Adequate correlations across whole Cropping District
– Stronger correlations when stratified by region
– Relationship to Cover Rating changes with season
– Strong relationships UAVI vs Cover rating when soil exposure high
Place and Purpose Symposium 2009
1
2
3
4
5
6
7
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0 0.2 0.4
UAVI
Co
ver
Rat
ing
2003 March 09
Relationship between Vegetation Index and Cover Rating changes through seasons
Clarke, K., Lewis, M. and Ostendorf, B. (2004, rev. 2009) Report 2: Assessing the potential of MODIS imagery for monitoring landcondition in the crop lands and non pastoral lease rangelands of South Australia. Land condition monitoring reports. Adelaide,
The University of Adelaide.
Bare soil
Full cover
Place and Purpose Symposium 2009
1
2
3
4
5
6
7
8
0 0.2 0.4
UAVI
Co
ver
Rat
ing
2003 March 09
2003 June 11
Relationship between Vegetation Index and Cover Rating changes through seasons
Clarke, K., Lewis, M. and Ostendorf, B. (2004, rev. 2009) Report 2: Assessing the potential of MODIS imagery for monitoring landcondition in the crop lands and non pastoral lease rangelands of South Australia. Land condition monitoring reports. Adelaide,
The University of Adelaide.
Bare soil
Full cover
Place and Purpose Symposium 2009
Relationship between Vegetation Index and Cover Rating changes through seasons
1
2
3
4
5
6
7
8
0 0.2 0.4 0.6
UAVI
Co
ver
Rat
ing
2003 March 09
2003 June 11
2003 October 12
R2 = 0.65
Clarke, K., Lewis, M. and Ostendorf, B. (2004, rev. 2009) Report 2: Assessing the potential of MODIS imagery for monitoring landcondition in the crop lands and non pastoral lease rangelands of South Australia. Land condition monitoring reports. Adelaide,
The University of Adelaide.
Bare soil
Full cover
Place and Purpose Symposium 2009
Relationship between Vegetation Index and Cover Rating changes through seasons
Region/ March May July October All
index 2006 2006 2006 2006 2006
NDVI
Eyre Peninsula -0.038 -0.286 *** -0.353 *** -0.425 *** -0.108
Murraylands +0.031 -0.281 *** -0.371 *** -0.241 *** -0.124 *
Northern and Yorke -0.032 -0.251 *** -0.296 *** -0.374 *** +0.052
South East +0.076 -0.031 -0.065 +0.007 -0.196 **
All regions combined -0.122*** -0.305 *** -0.382 *** -0.234 *** -0.022
UAVI
Eyre Peninsula -0.223 ** -0.304 *** -0.305 *** -0.407 *** -0.187 **
Murraylands -0.098 -0.275 *** -0.381 *** -0.143 *** -0.241 ***
Northern and Yorke -0.358 *** -0.365 *** -0.277 *** -0.372 *** -0.278 ***
South East +0.023 -0.054 -0.094 +0.052 -0.037
All regions combined -0.201 *** -0.339 *** -0.398 *** -0.258 *** -0.211 ***
p * 0.05
** 0.01
*** 0.001
Clarke, K. and Lewis, M. (2009) Report 3: Development of a satellite image-based land condition monitoring system for South Australian agricultural regions. Land condition monitoring reports. Adelaide, The University of Adelaide.
Spearman Rank Correlation Coefficients
Place and Purpose Symposium 2009
Key technical findings
1. UA Vegetation Index best predictor of Cover Rating
– NDVI doesn’t discriminate bare soil from dry stubble
– PD54 difficult to calibrate over time, difficult for operational use
2. Relationships between image indices & Cover Rating from field survey
– Adequate correlations across whole Cropping District
– Stronger correlations when stratified by region
– Relationship to Cover Rating changes with season
– Strong relationships UAVI vs Cover rating when soil exposure high
3. Large proportion of variation in cover/soil exposure is explained by climate (intra-& inter-annual variation)
– Seasonal index profiles track land cover changes through year
– Possible to identify land management influences as deviation from regional mean
Place and Purpose Symposium 2009
Annual profiles of image indices
Place and Purpose Symposium 2009
Annual profiles of image indices
• Summer (no growth, NPV decay)
Place and Purpose Symposium 2009
Annual profiles of image indices
• Summer (no growth, NPV decay)
• Germination (weed & non-cereal crops)
Place and Purpose Symposium 2009
Annual profiles of image indices
• Summer (no growth, NPV decay)
• Germination (weed & non-cereal crops)
• Ploughing, spraying off, direct seeding
Place and Purpose Symposium 2009
Annual profiles of image indices
• Summer (no growth, NPV decay)
• Germination (weed & non-cereal crops)
• Ploughing, spraying off, direct seeding
• Cereal crop germination and tillering & growth to full canopy
Place and Purpose Symposium 2009
Annual profiles of image indices
• Summer (no growth, NPV decay)
• Germination (weed & non-cereal crops)
• Ploughing, spraying off, direct seeding
• Cereal crop germination and tillering & growth to full canopy
• Crop ripening (senescence) and harvest
Place and Purpose Symposium 2009
Annual profiles of image indices
• Summer (no growth, NPV decay)
• Germination (weed & non-cereal crops)
• Ploughing, spraying off, direct seeding
• Cereal crop germination and tillering & growth to full canopy
• Crop ripening (senescence) and harvest
• Summer (NPV decay)
Place and Purpose Symposium 2009
Importance of climatic influence
Relationship between AUSSIEGrass model & Cover rating
Seasonal
Cover RatingMarch
May
June
October
Grech, A., Ostendorf, B. and Lewis, M. (2003) Report 1: Land condition monitoring: integrating ground surveys, Aussie GRASS and satellite remote sensing. Land condition monitoring reports. Adelaide, The University of Adelaide.
Rainfall
+ Total Pasture Growth
+Total Standing Dry Matter
Place and Purpose Symposium 2009
Importance of climatic influence
Grech, A., Ostendorf, B. and Lewis, M. (2003) Report 1: Land condition monitoring: integrating ground surveys, Aussie GRASS and satellite remote sensing. Land condition monitoring reports. Adelaide, The University of Adelaide.
Cover Rating 2001 predicted from AussieGRASS model developed with 2000, 2002, 2003 data
Place and Purpose Symposium 2009
Average annual UAVI (2006)
Clarke, K. and Lewis, M. (2009) Report 3: Development of a satellite image-based land condition monitoring system for South Australian agricultural regions. Land condition monitoring reports. Adelaide, The University of Adelaide.
Place and Purpose Symposium 2009
Cumulative difference from regional mean UAVI: Murraylands
Place and Purpose Symposium 2009
Cumulative difference from regional mea UAVI : Northern and Yorke
• Demonstrates local management influence
– Snowtown example
Place and Purpose Symposium 2009
Land management influences on cover detected by UAVI
Place and Purpose Symposium 2009
Land management influences on cover detected by UAVI
Place and Purpose Symposium 2009
Methodological findings
• Oblique view
• Ranked classes of Cover Rating – not a direct measure of projected cover
• Surveyor variability
• Vertical view
• Integrated response of projected soil & vegetation cover
• Objective, calibrated repeatable
Windsceen Survey data
Image indices
Advantages
• Extensive field survey data available
• Familiarity of field method
Disadvantages
• Field & image indices measure soil/cover in different ways
• Error, variability in field data not known
• Need independent cover data for calibration & validation
• Calibration relationship Cover Rating/Image Index not possible
Place and Purpose Symposium 2009
Institutional change process
• Considerable shift in organizational understanding & acceptance of remote sensing approach
– Collaboration in projects
– Sharing of data, findings
– Increased investment in research
• Personnel change a significant factor – new staff with remote sensing backgrounds
Place and Purpose Symposium 2009
The future
• Current ARC Linkage project
– Extend MODIS temporal analysis 2001-present
– Relative Spectral Mixture Analysis: time traces of soil, photosynthetic, non-photosynthetic vegetation
– Identify management influences on soil exposure through comparison of actual vs. climatically-predicted cover
• Relationships with Australian Collaborative Land use and Management Program (ACLUMP): development of field and remote sensing methods for monitoring fractional landcover
• Development of reporting products, information delivery with DWLBC
Place and Purpose Symposium 2009
Acknowledgements
Researchers
• Ken Clarke
• Bertram Ostendorf
• Alana Grech
Collaborators – DWLBC
• Anna Dutkiewicz
• Giles Forward
• Glenn Gale
• Andy McCord
• Richard Payne
Funding
• Soil Conservation Council
• Dept. Water Land & Biodiversity Conservation
• Australian Research Council
The Environment Institute