Soil Carbon: a Critical Natural Resource – Wide-scale Goals, Urgent Actions - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 15

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Fig. 2.2. Relative importance of possible threats to soil biodiversity in Europe as estimated by 20 soil
biodiversity experts. (From Jeffery et al ., 2010.)

benefit local people and wider communities
(George et al ., 2012). The goal here is to
maintain or enhance the biodiversity of
ecosystems by increasing SOC.
To date, conservation efforts to halt on-
going losses of global biodiversity have
largely ignored critical interactions between
the above- and belowground components of
biodiversity. In part, this reflects a historical
lack of information on the detailed compos-
ition and biogeography of soil communities.
The application of molecular methods in
large-scale surveys has begun to address this
knowledge gap (Coleman and Whitman,
2005). The soil is estimated to be the largest
terrestrial reserve of biodiversity (Fitter
et al ., 2005), with over one-quarter of the
species on Earth living in the soil (Jeffery
et al ., 2010). The soil biota make up a com-
plex food web consisting of microorganisms
(e.g. bacteria, fungi, archaea, protozoa) through
invertebrates (from nematodes to earthworms
and termites) to mammals and reptiles (e.g.
moles, snakes).
Soil biodiversity is important to soil qual-
ity since it has critical functional roles in the
cycling of nutrients, organic matter and water,
and in regulating soil structure, greenhouse
gas fluxes, pest control and the degradation of
pollutants. It is the presence of functional
groups rather than taxonomic richness that

appears to be important in soil C dynamics
(Nielsen et al ., 2011). Some of the main
functional groups include litter fragment-
ers, decomposers of complex organic com-
pounds, nitrifiers/denitrifiers, methanogens/
methanotrophs and ecosystem engineers.
Although we know these groups exist and
we are rapidly gaining understanding about
their roles in above- and belowground pro-
cesses (Cornelissen et al ., 2001; van der
Heijden et al ., 2008; Strickland et al ., 2009),
we still lack the ability to predict how, when
and where these functional groups determine
the capacity of soils to capture and store car-
bon and exchange greenhouse gases (Hunt
and Wall, 2002).
This soil system derives its primary
energy from carbon substrates obtained
from root exudates, direct photosynthesis
and the decomposition of organic matter
from litter and plant roots. Thus, the quan-
tity and quality of soil carbon is a key factor
in determining the structure and activity of
the soil community, and vice versa (Schulze,
2006). Changes in agricultural practices for
food, livestock or bioenergy production af-
fect SOC and disrupt both the below- and
aboveground biodiversity. Practices to in-
crease or maintain biodiversity include
the protection of natural resources, halt-
ing land-use changes that affect natural