Chemistry Reference
In-Depth Information
morphological taxonomy can be hampered by cryptic speciation and other
taxonomic uncertainties.
Beyond these better-known groups, in taxa like mites and nematodes there
are significant issues for morphological identification associated with the lack
of keys, laborious nature of the work and declining expert base. Because they
are often poorly known, few soil species are recognised for their conservation
value. A few, such as some ants and fungi, are covered by the UK Biodiversity
Action Plan
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(UK BAP). However, as knowledge of soil biodiversity is often
sparse, it is not well known if and how climate, land use, land management
change and pollution affect populations of even these relatively well known
and highly valued species, let alone the large amount of often hidden diversity
that maybe present in soils. Beyond the few soil species covered by BAPs, there
is a well-recognised need to quantify soil biodiversity and determine whether it
is possible to observe consistent patterns of population and community
structure against a dynamic background of spatial and seasonal variability.
Key questions relate to determining if and how soil biodiversity changes over
time, and the nature of the environmental drivers of any such changes.
National-scale surveys of soil biodiversity are relatively rare in the published
literature
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. Soil invertebrates have been identified and counted in two
Countryside Survey project in 1998 and 2007, with the focus on measuring the
abundance and broad taxa richness of the soil mesofauna. In the most recent
survey in 2007, there were an estimated 12.8 quadrillion (1.28 6 10
16
) soil
invertebrates present in the top 8 cm of the soils of Great Britain during the
time of sampling. Comparing these results with those from the survey in 1998
enabled change in soil biodiversity to be estimated at a national scale. A
significant increase in total invertebrate catch in samples from soils (0-8cm)
from all Broad Habitats, Aggregate Vegetation Classes and soil organic matter
categories, except for agricultural areas on mineral soils, was found in the
Countryside Survey in 2007. The increase in invertebrate catch was mainly the
result of an increase in the catch of mites in 2007 samples. This resulted in an
increase in the mite: springtail ratio, but a decreased Shannon diversity due to
the dominance of mites in 2007 cores. A small reduction in the number of soil
invertebrate broad taxa was found, which could suggest that there may be a
declining trend in soil biodiversity. However, repeat sampling is required to
ensure that seasonal conditions in the two sampling years, including land
management, annual weather patterns or merely natural population variation,
do not explain the observed changes before any general trends can be
validated. Individual site studies with time-series data would be a useful place
to start in this regard.
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Large-scale changes in soil biodiversity would undoubtedly have important
consequences for ecosystem services delivered by the soil. However, these
services provided by soil organisms are generally undervalued in agricultural
systems since it is human inputs rather than natural processes that are
considered to drive the system. For example, it was estimated that earthworms
add 723 million euros per year to livestock production in Ireland.
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