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# | Presentation
Soils have become one of the world's most vulnerable resources in the face of climate change, land degradation, biodiversity loss and increased demand for food production. The role of soils and soil organic carbon (SOC) in the climate system and climate change adaptation and mitigation has been recognized widely and validated in various studies, both experimentally and through modelling. Maintaining and increasing SOC stocks is not only crucial for reducing greenhouse gas (GHG) emissions and removing CO~2~ from the atmosphere but also for harnessing the benefits of increased SOC (and soil organic matter - SOM) for soil health and fertility by improving water storage and thereby increasing the access of plants to water, food production potential and resilience to drought (FAO, 2017). It may lead to changes in health threat to human beings, and poses a significant challenge to rural communities and to our ability to thrive on our planet. The widespread adoption of site-specific sustainable soil management (SSM) practices in agricultural lands can harness a large C sink capacity at the global scale and its role as an effective strategy to mitigate GHG has been widely documented.
The magnitude and rate of carbon sequestration in soils can vary greatly, depending on the different land uses and practices, soil characteristics, vegetation, topography and climate, among other soil forming factors and processes. It is thus relevant to identify which regions, environments and production systems have a greater potential to increase SOC stocks as well as establishing priorities for research and the implementation of public policies.
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 Global Soil Partnership (GSP) Plenary Assembly in 2020 instructed the Intergovernmental Technical Panel on Soils (ITPS) and the GSP Secretariat to develop the Global Soil Organic Carbon Sequestration Potential map (GSOCseq map), following the same country-driven approach developed for the Global Soil Organic Carbon map (GSOCmap). This 'bottom-up' approach is expected to generate a GSOCseq map from national SOCseq maps, developed and validated by local experts, based on the implementation of SOC models using standardized procedures and by leveraging the best available local data.
To this end, members under the International Network of Soil Information Institutions (INSII) umbrella developed general guidelines and technical specifications for the preparation of the GSOCseq map and countries were invited to prepare their national soil organic carbon sequestration potential maps according to these specifications. Given the scientific advances in the tools for modeling and mapping SOC, many countries requested the GSP Secretariat to support them in the process of preparing national SOCseq maps. Hence, an intensive capacity development program on SOC sequestration potential through the use of modelling and mapping techniques is being implemented. Regional and national training sessions are being organized using an on-the-job-training modality to ensure that national experts are trained on the state of the art modeling and mapping techniques using their own data sets to produce reliable SOCseq maps.
This Technical Manual was prepared as a comprehensible reference knowledge base to support the capacity development process. It provides the necessary background knowledge, methodologies and technical steps to produce national SOCseq maps. It includes step-by-step guidance for developing 1 km grids of SOC sequestration potential, as well as for the preparation of local data and the compilation and preprocessing of spatial data sets, using open source software environments and tools.
This Technical Manual supplements the Technical Specifications and Country Guidelines for Global Soil Organic Carbon Sequestration Potential Map (GSOCseq), (FAO and GSP, 2020), and part of its contents is included in the current Manual.
It is our hope that this Technical Manual will fulfill its mandate of easily enabling any user to produce digital SOC sequestration maps using soil legacy data, process oriented SOC models and modern techniques of digital soil mapping and realize the overall aim of improving decision making on soil management.
## How to use this book
This Manual is organized in 13 Chapters, including this one. Chapter 2 provides scientific background on the importance of SOC sequestration as a GHG mitigation strategy, factors that regulate SOC sequestration and finally how it can be estimated. Chapter 3 provides scientific background on the use of different SOC models to estimate SOC changes and SOC sequestration potential. Chapter 4 describes one of the most used process-oriented SOC models, to be used as a standard to allow comparisons between countries: the RothC model. Chapter 5 describes the general modeling procedures to generate national SOCseq maps using this SOC model. Chapter 6 describes the required data sets, potential data sources and methodologies to estimate modeling inputs for the modeling approach described in Chapter 5. Chapter 7 gives an overview of the steps and software requirements to generate national SOCseq maps using a spatially explicit R-version of the RothC model. Chapters 8 to 11 constitute the core of this document, providing a step by step guide on how to run the R-scripts and generate the final product:
* Chapter 8 summarizes the different steps and scripts to be used during the complete process;
* Chapter 9 summarizes the procedures and scripts harmonization and preparation of input data;
* Chapter 10 summarizes the procedures for running the model from the prepared data;
* Chapter 11 summarizes the procedures for the generation of the final maps from the modeling runs.
Chapter 12 provides an overview for the estimation of uncertainties. Lastly, Chapter 13 summarizes the procedure for the sharing of the national SOCseq maps.
## The sample data set
The sample data set provided with this Technical Manual was compiled to model and map the potential soil organic carbon sequestration for the district of Pergamino, Buenos Aires. It covers an area of 2,950 km^2^ that is mainly dedicated to agriculture. Pergamino is located in the Corn Belt of Argentina and with its subtropical climate it is favorable for double cropping systems, allowing for two harvests a year. The lowlands of this district are used mainly as pastures for the production of calves.
This Technical Manual used in combination with the provided sample data set and scripts can be used as a step-by-step guide, which covers data preparation and harmonization, modeling potential soil organic carbon sequestration, rasterizing the results, estimating the uncertainty and finally data sharing.
The sample data set and scripts can be found in the following repository:
https://drive.google.com/drive/folders/1Jonn17LAiCyaUSpUn6W63o16bjTg1P0E?usp=sharing
More information on the necessary data and the provided data set can be found in Chapter 6, while an overview of the different steps and scripts needed is presented in Chapter 8.