Chapter 1
Presentation
Soils provide ecosystem services critical to life on Earth. The Food and Agricultural Organization of the United Nations (FAO) recognizes the need to preserve soil resources from degradation and boost healthy soils. In 2012, FAO members established the Global Soil Partnership (GSP) as a mechanism to improve soil governance at global, regional and national levels.
The GSP aims to promote sustainable soil management at all levels through different means including normative tools, capacity development, international events
and field projects relying on evidence-based science. Understanding the status of
a given soil in different land uses, including its properties and functions, and relating this information to the various ecosystem services provided by them, becomes
mandatory for sustainable soil management decisions. As the availability of soil
data and information is fundamental to underpin these decisions, partners of the
GSP decided to establish a Global Soil Information System (GLOSIS) based on a
distributed model whereby the system is fed by national soil information systems.
In the process of establishing GLOSIS, a number of components are being established, including the International Network of Soil Information Institutions
(INSII), a GSP Soil Data Policy (FAO and GSP, 2017b) and the Pillar 4 working group. Taking advantage of this process and responding to a request for support in addressing the Sustainable Development Goal Indicators, especially indicator 15.3 which includes the restoration of degraded soils, the GSP Plenary Assembly in 2016 instructed the Intergovernmental Technical Panel on Soils (ITPS) and the GSP Secretariat to develop the first-ever Global Soil Organic Carbon map (GSOCmap) following the same bottom-up approach as GLOSIS. To this end, members under the INSII umbrella developed guidelines and technical specifications for the preparation of the GSOCmap and countries were invited to prepare their national soil organic carbon maps according to these specifications. Given the scientific advances in tools for mapping soil organic carbon (SOC), many countries requested the GSP Secretariat to support them in the process of preparing national SOC maps, hence an intensive capacity development programme onSOC mapping has been implemented to support countries in this process. Various regional and national training sessions were organized using an on-the-job-training modality to ensure that national experts be trained on the state of the art digital soil mapping techniques using their own datasets to produce reliable SOC maps. The GSP Secretariat invited a group of experts to prepare the first edition of a Soil Organic Carbon Mapping Cookbook (FAO, 2017) as a comprehensible reference knowledge source to support the capacity development process. The second edition of the cookbook provides generic methodologies and technical steps to produce SOC maps. This edition has been updated with knowledge and practical experiences gained during the implementation process of GSOCmap V1.0 throughout 2017. The cookbook includes step-by-step guidance for developing 1 km grids for SOC stocks, as well as for the preparation of local soil data, the compilation and preprocessing of ancillary spatial data sets, upscaling methodologies, and uncertainty assessment methods. Guidance is mainly specific to SOC data, but as this cookbook contains generic sections on soil grid development, it can be applicable to map various soil properties using digital soil mapping techniques. The guidance focuses on the upscaling of national SOC stocks in order to produce the GSOCmap. Therefore, the cookbook supplements the GSP Guidelines for Sharing National Data/Information to Compile a Global Soil Organic Carbon (GSOC) Map (FAO and GSP, 2017a), providing technical guidelines to prepare and evaluate spatial soil data sets in order to:
(INSII), a GSP Soil Data Policy (FAO and GSP, 2017b) and the Pillar 4 working group. Taking advantage of this process and responding to a request for support in addressing the Sustainable Development Goal Indicators, especially indicator 15.3 which includes the restoration of degraded soils, the GSP Plenary Assembly in 2016 instructed the Intergovernmental Technical Panel on Soils (ITPS) and the GSP Secretariat to develop the first-ever Global Soil Organic Carbon map (GSOCmap) following the same bottom-up approach as GLOSIS. To this end, members under the INSII umbrella developed guidelines and technical specifications for the preparation of the GSOCmap and countries were invited to prepare their national soil organic carbon maps according to these specifications. Given the scientific advances in tools for mapping soil organic carbon (SOC), many countries requested the GSP Secretariat to support them in the process of preparing national SOC maps, hence an intensive capacity development programme onSOC mapping has been implemented to support countries in this process. Various regional and national training sessions were organized using an on-the-job-training modality to ensure that national experts be trained on the state of the art digital soil mapping techniques using their own datasets to produce reliable SOC maps. The GSP Secretariat invited a group of experts to prepare the first edition of a Soil Organic Carbon Mapping Cookbook (FAO, 2017) as a comprehensible reference knowledge source to support the capacity development process. The second edition of the cookbook provides generic methodologies and technical steps to produce SOC maps. This edition has been updated with knowledge and practical experiences gained during the implementation process of GSOCmap V1.0 throughout 2017. The cookbook includes step-by-step guidance for developing 1 km grids for SOC stocks, as well as for the preparation of local soil data, the compilation and preprocessing of ancillary spatial data sets, upscaling methodologies, and uncertainty assessment methods. Guidance is mainly specific to SOC data, but as this cookbook contains generic sections on soil grid development, it can be applicable to map various soil properties using digital soil mapping techniques. The guidance focuses on the upscaling of national SOC stocks in order to produce the GSOCmap. Therefore, the cookbook supplements the GSP Guidelines for Sharing National Data/Information to Compile a Global Soil Organic Carbon (GSOC) Map (FAO and GSP, 2017a), providing technical guidelines to prepare and evaluate spatial soil data sets in order to:
• Determine SOC stocks from local samples to a target depth of 30 cm;
• Prepare spatial covariates for upscaling; and
• Select and apply the best suitable upscaling methodology.
In terms of statistical upscaling methods, the use of conventional upscaling methods using soil maps and soil profiles is still very common, although this approach is
mostly considered empirical by soil mappers. Even though evaluations are based
on polygon soil maps, the resulting SOC maps can be rasterized to any target grid.
However, a spatially-explicit assessment of uncertainties is impossible. The use of
digital soil mapping to upscale local soil information is increasingly applied and
recommended.
This cookbook presents two approaches in detail, namely spatial modelling using either regression or data mining analysis, combined with geostatistics such as
regression-kriging. The second edition includes updates on uncertainty assessment
of the presented methods.
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