Measuring and Monitoring Soil Carbon - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 188

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Measuring and Monitoring
Soil Carbon

Niels H. Batjes* and Bas van Wesemael

Abstract
Soils are the largest terrestrial reservoir of organic carbon, yet great uncertainty remains in estimates
of soil organic carbon (SOC) at global, continental, regional and local scales. Compared with biomass
carbon, changes in SOC associated with changes in land use and management, or climate change, must
be monitored over longer periods. The changes are small relative to the very large stocks present in the
soil, as is their inherent variability. This requires sensitive measurement techniques and due consid-
eration for the minimum detectable difference (MDD). Relationships between environmental and man-
agement factors and SOC dynamics can be established using experimental field trials, chronosequence
studies and monitoring networks. Soil monitoring networks (SMNs), for example, can provide infor-
mation on direct changes of SOC stocks through repeated measurements at a given site, as well as data
to parameterize and test biophysical models at plot scale. Further, they can provide a set of point ob-
servations that represent the (mapped) variation in climate/soil/land use and management at national
scale, allowing for upscaling. SMNs must be designed to detect changes in soil properties over relevant
spatial and temporal scales, with adequate precision and statistical power. Most SMNs, however, are
in the planning or early stages of implementation; few networks are located in developing countries,
where most deforestation and land-use change is occurring. Within these monitoring networks, sites
may be organized according to different sampling schemes, for example regular grid, stratified ap-
proach or randomized; different statistical methods should be associated with each of these sampling
designs. Overall, there is a need for globally consistent protocols and tools to measure, monitor and
model SOC and greenhouse gas emission changes to allow funding agencies and other organizations
to assess uniformly the possible effects of the impacts of land-use interventions, and the associated
uncertainties, across the range of world climate, soils and land uses.

Introduction

largest terrestrial reservoir of organic car-
bon, great uncertainty remains in the esti-
mates of soil organic carbon (SOC) stocks
and their changes at global, continental,
regional and local scales (Kogel-Knabner
et al ., 2005; Milne et al ., 2010; Paustian,
2012; Smith et al ., 2012). Hence the need for

Soils are needed for the production of food,
fibre and timber, and they provide many
ecosystem services, largely through the
beneficiary functions of soil organic matter
(Victoria et al ., 2012). Although soils are the