Basic Principles of Soil Carbon Management for Multiple Ecosystem Benefits - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 266

during the crop phase of the rotation and to
replenish nutrient reserves during the
non-cropping phase (Whitbread et al ., 2000).
The rotation of field crops and grass fallows
conferred stability to the soil system and
was a sustainable agricultural production
system until the advent of inorganic fertil-
izers, herbicides, genetic improvement for
high-yielding crops and technological in-
novation of mechanized tillage and other
field operations, which all together consti-
tuted the so-called 'green revolution'. These
global changes in agriculture brought about
a substantial improvement in food produc-
tion, but also produced a decoupling of the
biological processes in the soil and essential
nutrient concentrations (Tonitto et al .,
2006). The availability of inexpensive syn-
thetic nitrogen sources and efficient herbi-
cides promoted this trend and enabled vast
areas of the world's most productive land to
be cultivated to one type of crop for pro-
longed periods (Tilman et al ., 2002). The in-
herent problem associated with this type of
land management is a drastic reduction of
aboveground plant diversity, which also re-
sults in a decline of soil microbial activity
and diversity (Milcu et al ., 2010), and thus
in a loss of vital soil functions (Nielsen
et al ., 2011). Biomass production, protec-
tion of humans and the environment, gene
reservoir, physical basis of human activ-
ities, source of raw materials and geogenic
and cultural heritage have been identified
as key soil functions (Blum, 2005). Soils are
living bodies and their multiple ecosystem
functions are intimately related to SOM
transformations and dynamics, which are
mediated by soil biotic activity and soil
structural dynamics (Six et al ., 2002b).
Hence, soil management for multiple eco-
system services needs to focus on the link
between SOM, soil structure and soil biota,
and the regulating factors of this link (Six
et al ., 2004; Wardle et al ., 2004).
Recently, there has been a strong focus
on SOM as a reservoir for C and a mechan-
ism of C sequestration and climate change
protection (Lal, 2004; Powlson et al ., 2011),
but far less emphasis has been placed on
managing the regulating, cultural and sup-
porting ecosystem services. The importance

of soil carbon in relation to addressing
pressing global issues through the provi-
sioning of various ecosystem services has
only recently been recognized by policy
makers (Victoria et al ., 2012).

The Soil's Natural Capital and
Related Ecosystem Services

The term 'natural capital' was brought to
prominence by Robert Costanza (Costanza
et al ., 1997), who defined natural capital as
'the extension of the economic notion of
capital (manufactured means of production)
to environmental goods and services. A func-
tional definition of capital in general is: a
stock that yields a flow of valuable goods or
services into the future. Natural capital is
thus the stock of natural ecosystems that
yields a flow of valuable ecosystem goods or
services into the future. For example, a
stock of trees or fish provides a flow of new
trees or fish, a flow that can be sustained in-
definitely. Natural capital may also provide
services like recycling wastes or water cap-
ture and erosion control. Since the flow of
services from ecosystems requires that they
function as whole systems, the structure
and diversity of the system are important
components of natural capital' ( http://www.
eoearth.org/article/Natural_capital, accessed
22 January 2013).
Only recently, these concepts have
been applied to soils (Dominati et al ., 2010;
Robinson et al ., 2012), despite the obvious
relevance of natural capital and ecosystem
services to soil science. The lack of consist-
ent typology or terminology for ecosystem
services means that properties, processes,
functions and services become used inter-
changeably, leading to confusion (Robinson
et al ., 2012), and often the focus on final
goods and services ignores the importance
of soils in their delivery. In an attempt to
clarify the concepts and develop a natural
capital-ecosystem services framework for
soils, Dominati and colleagues (Dominati
et al ., 2010) defined the soils' natural cap-
ital through its inherent physical properties
such as depth, clay contents and type, along