Measuring and Monitoring Soil Carbon - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 189

a better understanding and quantification
of the role of soils and the vegetation they sup-
port as natural regulators of greenhouse gas
(GHG) emissions and climate change. Docu-
menting such changes requires methodolo-
gies for monitoring, reporting and verification
(MRV) of C stocks and GHG emissions
that follow the principles of the United
Nations Framework Convention on Climate
Change (UNFCCC): transparency, consist-
ency, comparability, completeness and ac-
curacy ( Bottcher et al ., 2009). The relative
importance of accurate measurement of the
different carbon pools will vary across land-
cover types (IPCC, 2006; Ravindranath and
Ostwald, 2008; GOFC-GOLD, 2009; de Brog-
niez et al ., 2011). In this respect, the IPCC
National Accounting Guidelines recommend
prioritizing the measurement and monitor-
ing of the most significant carbon pools and
those with the greatest potential to change
(IPCC, 2006).
Soil properties vary in space, with depth
and over time, with different measurement
errors attached to them (Burrough, 1993).
Soil monitoring involves the systematic
measurement of soil properties to record
their spatial and temporal changes. The as-
sessment of SOC stock (changes), at a given
site or for a given region, will require analyses
of OC concentration, bulk density, content of
coarse fragments (>2 mm) and soil depth. To
be most effective, however, monitoring activ-
ities should consider a larger set of soil vari-
ables (e.g. Morvan et al ., 2007), as well as
information on the main biophysical (climate,
terrain, soils and land use/vegetation or 'activ-
ity' data) and socio-economic drivers of change
(e.g. Lambin, 1997; Ravindranath and Ostwald,
2008; de Brogniez et al ., 2011). These vari-
ables may be recorded within the framework
of a larger soil monitoring network (SMN) or
a specific land use and management project.
They are also needed for modelling possible
changes in SOC stocks and GHG emissions us-
ing a range of empirical and process-based tools
(see Chapter 17, this volume).
Several steps are needed in any meas-
urement protocol to produce credible and
transparent estimates of net changes in carbon
stocks. These include: (i) designing a monitor-
ing plan, including delineation/mapping of

(project) boundaries, stratification of the pro-
ject area, determining the type and number
of sample plots, selection of C pools to be
considered and appropriate procedures for
their measurement, and frequency of monitor-
ing; (ii) sampling procedures for field data
collection for estimating above- and below-
ground carbon stocks (mainly, above- and
belowground tree biomass; dead wood in
standing and downed trees; non-tree vegeta-
tion; litter and duff; and SOC). In addition to
this, consistent procedures are needed to
analyse the results; for soil properties, these
should include a quality assurance and qual-
ity control plan (IPCC, 2006; Ravindranath
and Ostwald, 2008; de Brogniez et al ., 2011).
The focus of this chapter is on monitoring
soil carbon changes.
Key issues on SOC monitoring and
sampling/analysis approaches are discussed
in this paper, based on a review of the recent
literature. Drawing from this, main methodo-
logical requirements and general recom-
mendations are proposed for 'good soil
monitoring practice'.

Soil Monitoring Networks

Purpose

The primary reasons for collecting most
forms of natural resources data are to reduce
risks in decision making and to improve the
understanding of biophysical processes (Mc-
Kenzie et al ., 2002; Ravindranath and Ost-
wald, 2008; de Brogniez et al ., 2011). Soil
monitoring may be defined as the systematic
measurement of soil properties with a view
to recording their temporal and spatial vari-
ations. SMNs generally comprise a set of
sites/areas where changes in soil characteris-
tics are documented through periodic assess-
ment of an extended set of properties (Morvan
et al ., 2008; Arrouays et al ., 2012). To be most
effective, SMNs have to be integrated with other
activities that generate essential knowledge
for natural resource management, including
land resource surveys, environmental/land-use
history, field experiments and simulation mod-
elling (Morvan et al ., 2008; Ravindranath
and Ostwald, 2008; Desaules et al ., 2010).