Geoscience Reference
In-Depth Information
taxa in a given ecosystem Bardgett et al. (2008). Only then can
we begin to predict whether a particular soil is a net carbon
emitter or sink based on microbial ecology.
This approach can be further expanded by combining
metagenomics with SIP to find out the specific functions of
a microbial population in a community. Future work should
attempt to use this approach to differentiate between popu-
lations that use labile carbon and those that promote carbon
sequestration. In agriculture, the often large losses of soil
organic carbon owing to cultivation can be reduced by low- and
no-tillage practices, which favour soil communities dominated
by fungi (Castro et al., 2010); such agroecosystems prevent the
increase in microbial decomposition and respiration.
Reducing Ch
4
emissions by
microbial
communities
Our understanding of the microbiology of greenhouse gas
cycling is more complete for CH
4
than for CO
2
or N
2
O, as the
pathway is simple and specialised microorganisms are involved.
However, many of the above uncertainties also apply to the
management of terrestrial CH
4
fluxes, because most atmo-
spheric CH
4
is produced by microorganisms, it is theoretically
feasible to control a substantial proportion of CH
4
emissions
from terrestrial ecosystems by managing microbial community
structure and processes Phillips et al. (2001). The biological
oxidation of CH
4
by methanotrophs accounts for only ~5% of
the global sink of atmospheric CH
4
(~30 million tonnes per
year) (Hanson and Hanson, 1996) and may therefore seem less
important. However, methanotrophs are also responsible for
the oxidation of up to 90% of the CH
4
produced in soil before
it can escape to the atmosphere (Oremland and Culbertson,
1992). It is well established that conversion of arable land or
grassland into a forest results in a substantial reduction in CH
4
flux (Kolbs, 2009), and it is evident that both the type and
abundance of methanotrophs are important for predicting CH
4
flux. However, no current climate model considers this find-
ing, so future research must focus on incorporating these data
and interactions to improve predictions of CH
4
fluxes across
various ecosystems. This knowledge can also be applied to the
reduction of CH
4
emissions by changing land use and man-
agement. In rice cultivation, for example, methanotrophs have
long played a crucial part in absorbing a proportion of the CH
4
produced and, as a result, improved management of flooding
frequency and duration could reduce net emissions by increas-
ing oxygen availability in soils (Yagi, 1996; Reay, 2003). There
is also a great potential to make effective use of inhibitors of
methanogenesis, such as ammonium sulphate fertilisers, in
