soil carbon mapping in australia

Soil carbon mapping in Australia

CSIRO AGRICULTURE & FOOD

Neil McKenzie with contributions from Ross Searle, Mike Grundy and Raphael Viscarra RosselCSIRO Australia

Overview

• Information on soil carbon stocks in space and time affects major decisions by governments and industries in Australia• There has been a steady evolution of methods and products at

the national level• The ‘official’ map of carbon stocks is not the only national map• New and improved scientific methods are being developed• Success has depended primarily on institutional and cultural

factors

Soil Carbon Meeting, FAO, 24 Nov 20162 |

Soil Carbon Meeting, FAO, 24 Nov 2016

Evolution of continental scale mapping

• The quality of estimation for most soil properties has improved significantly over the last 15 years

• Initial grids based on the national soil map (Atlas of Australian Soils)

• Several cycles of producing nationally gridded estimates via some form of environmental correlation

• Improvements in environmental covariates have been critical

• Involvement in international projects such as GlobalSoilMap has generated many benefits

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GlobalSoilMap in Australia• Estimates of functional soil properties,

particularly for modelling• Spatial resolution and format to match

other environmental data sets• Enduring and easy-to-update soil

information system with online access rather than a one-off product

• Best available soil and environmental data used to generate the estimates

• Complementary to existing soil information systems (e.g. polygons)

• Explicit estimate of uncertainty• The grid resolution is not the guide to

uncertainty (c.f. cartographic scale)

Advances in Agronomy Volume 125 (2014)



Soil and Landscape Grid of Australia (SLGA)

• Major project to produce gridded soil information consistent with the Technical Specifications of GlobalSoilMap• Includes extra variables

(e.g. total phosphorus)• See the special issue on the

Soil and Landscape Grid of Australia in Soil Research (2014) Volume 53

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www.clw.csiro.au/aclep/soilandlandscapegrid/

http://www.clw.csiro.au/aclep/soilandlandscapegrid/

The best approach depends on data availability

KSS Brisbane 26th October 2016 | Neil McKenzie6 |


Estimation methods for the SLGA a) Australia-wide using decision trees

with piece-wise linear models and kriging of residuals developed from soil site data, spectroscopic measurements and continental covariates

b) disaggregation of existing polygon soil mapping using DSMART (Western Australia)

c) disaggregation of existing polygon soil mapping using DSMART (South Australia)

d) decision trees with piece-wise linear models and kriging of residuals developed from soil site data and locally derived covariates (Tasmania).

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National Collation – 285 000 sites

Soil data used for SLGA

Attribute No. Samples

EC 189519pH Soil/water 141838Water soluble Cl 105515Organic carbon 96974Exch. Na+ 89884Exch. Ca++ 89452Exch. K+ 89277Exch. Mg++ 89155pH Soil/CaCl2 76243Total P 64470Clay 60325Silt 59776Moisture content 56590Total K 55284CEC 52397



Australia’s official map of soil carbon stocks

• Produced at the same time as the Soil and Landscape Grid of Australia (SLGA)• Estimates soil carbon stocks to 30 cm for a notional date of

2010• Different product to the SLGA and designed to be the official

soil map in Australia’s National Carbon Accounting System • Uses the bootstrap, a decision tree with piecewise regression

on environmental variables and geostatistical modelling of residuals • See Viscarra Rossel et al. (2014) Global Change Biology

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Three primary soil data sets used for the ‘official map’

• 4125 sites from Australia’s National Soil Carbon Research Programme (SCaRP): see Soil Research (2013) Vol 51 Special Issue• 1101 sites with

spectroscopic estimates of organic C and BD from the National Geochemical Survey of Australia (de Caritat et al., 2008)• 491 sites from the

National Soil Profile Database

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Soil carbon stocks (0–30cm)

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Uncertainty of the estimated carbon stock

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Total stock of organic carbon in Australian soils

Source Depth (cm) Estimate (Gt) Lower 95% CI

Upper 95% CI

Gifford et al. (1992) Rooting depth 51.8

Barrett (2002) 0-20 20.0

Barrett (2013) 0-100 26.9 20.3 33.5

Grace et al. (2006) 0-300-100

18.834.2

Viscarra Rossel et al. (2014)

0-30 24.97 19.04 31.83


Australia has 5.2% of global land area but only 3.5% of the global carbon stock (0-30cm)


Soil carbon estimates from the SLGA

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• Estimates of soil carbon from the Soil and Landscape Grid of Australia are different to the ‘official map’• Based on more data (number of

sites and deeper)• Issues of bias and time are

significant but not everywhere

Liddicoat et al. (2015) Soil Research 53, 956-973

Australia’s collaborative model: a foundation for success

• Australian Collaborative Land Evaluation Program (ACLEP) has operated for 25 years• Relatively informal arrangement between

national, state and territory agencies with oversight through a national technical committee• Various functions including training,

development of standards, assessment of soil condition, advocacy and facilitation of national projects• Funding for collaboration has mostly come

from the Australian Government



Factors supporting improved mapping of soil carbon in Australia

• Very strong soil carbon research community• Collection of key data sets on soil carbon in

the previous ten years• Active involvement in GlobalSoilMap• Development of the Soil and Landscape

Grid of Australia – especially the high-resolution environmental covariates• Ongoing research into pedometrics, digital

soil mapping and soil carbon assessment methods (e.g. University of Sydney)• Recent advances are improving estimation

at local through to global scales

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Thank you

CSIRO AGRICULTURE AND FOOD

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