Baseline estimates of soil organic carbon by proximal sensing: comparing design-based, model-assisted and model-based inference

Viscarra Rossel, R. A. and Brus, D. J. and Lobsey, C. and Shi, Z. and McLachlan, G. (2016) Baseline estimates of soil organic carbon by proximal sensing: comparing design-based, model-assisted and model-based inference. Geoderma, 265. pp. 152-163. ISSN 0016-7061

Abstract

For baselining and to assess changes in soil organic carbon (C) we need efficient soil sampling designs and methods for measuring C stocks. Conventional analytical methods are time-consuming, expensive and impractical, particularly for measuring at depth. Here we demonstrate the use of proximal soil sensors for estimating the total soil organic C stocks and their accuracies in the 0-10 cm, 0-30 cm and 0-100 cm layers, and for mapping the stocks in each of the three depth layers across 2837 ha of grazing land. Sampling locations were selected by probability sampling, which allowed design-based, model-assisted and model-based estimation of the total organic C stock in the study area. We show that spectroscopic and gamma attenuation sensors can produce accurate measures of soil organic C and bulk density at the sampling locations, in this case every 5 cm to a depth of 1 m. Interpolated data from a mobile multisensor platform were used as covariates in Cubist to map soil organic C. The Cubist map was subsequently used as a covariate in the model-assisted and model-based estimation of the total organic C stock. The design-based, model-assisted and model-based estimates of the total organic C stocks in the study area were similar. However, the variances of the model-assisted and model-based estimates were smaller compared to those of the design-based method. The model-based method produced the smallest variances for all three depth layers. Maps helped to assess variability in the C stock of the study area. The contribution of the spectroscopic model prediction error to our uncertainty about the total soil organic C stocks was relatively small. We found that in soil under unimproved pastures, remnant vegetation and forests there is good rationale for measuring soil organic C beyond the commonly recommended depth of 0-30 cm.


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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Files associated with this item cannot be displayed due to copyright restrictions.
Faculty / Department / School: No Faculty
Date Deposited: 29 May 2017 22:39
Last Modified: 02 Jun 2017 05:56
Uncontrolled Keywords: Design-based sampling; Infrared spectroscopy; Model-based inference; Proximal soil sensing; Regression estimator; Soil organic carbon stocks; Visible-near; Model-based OPC; Proximal soil sensing; Regression estimators; Soil organic Carbon stocks; Visible-near; ECOLOGICAL AND ENVIRONMENTAL SCIENCES; ECOLOGY OF COMMUNITIES/ECOSYSTEMS; Community/Ecosystem Processes; Nutrient cycling and decomposition; ECOLOGICAL AND ENVIRONMENTAL SCIENCES; TECHNIQUES; Sampling; Surveying; Soils and Soil Mechanics; Organic Compounds; Applied Mathematics; FLUIDEX; Related Topics;
Fields of Research : 05 Environmental Sciences > 0503 Soil Sciences > 050301 Carbon Sequestration Science
Socio-Economic Objective: D Environment > 96 Environment > 9614 Soils > 961499 Soils not elsewhere classified
Identification Number or DOI: 10.1016/j.geoderma.2015.11.016
URI: http://eprints.usq.edu.au/id/eprint/32007

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