Written by Lorna Dawson, David Miller and Willie Towers
For many years, improving
agricultural production was the main goal of soil science. As part of
this, a number of country-wide soil mapping programmes took place
across Europe during the 20th Century, which also resulted
in the creation of several national soil databases. Today, the
importance of these data, complemented in some countries with
irreplaceable archives, goes far beyond agriculture. They are proving
to be an invaluable resource for a wide range of applications - from
measuring the effects of climate change, monitoring environmental
pollution and atmospheric deposition, to helping solve serious
crimes.
Soil maps and
databases In the UK, truly national
soil sampling programmes (with the goal of mapping soil distributions
for agricultural purposes) started in England and Wales in 1939 and
Scotland in 1948, although not until 1987 in Northern Ireland.
Published soil
maps ranged in scale from 1:25,000 to 1:63,360, and included reports
incorporating information about the soils and their associated
landscapes and environments. Geographically, most of these are
concentrated on the higher quality agricultural land, which reflects
the early emphasis on agriculture and the desire to optimize the use
of those soils for food production. In the late 1970s, the focus of
attention for such mapping programmes moved to the production of soil
maps which would provide national coverage (1:250,000 scale) for the
whole of the Great Britain. These maps have subsequently been
digitized greatly increasing their utility and applications.
As this mapping programme
progressed, soil profiles were excavated in order to collect data
that characterised the soils being mapped. Currently, approximately
13,000 profiles to a depth of a metre are held within the Macaulay
Institute’s archive, comprising samples for approximately 40,000
soil horizons. The majority of these data were collected as being
representative of different soil types across the country and not a
strategy for the sampling of Scotland’s soils.
A core part of the
database is the National Soils Inventory of Scotland (NSIS). These
data were collected at every 5 km x 5 km grid intersection and offer
several advantages over data gathered using subjective judgements.
These include:
The NSIS provides a
framework for a structured re-sampling of soils to determine trends
of change, and to develop and test hypotheses on the drivers and
pressures that have caused those changes.
The NSIS sites were first visited between 20 and 30 years ago, at a
time of agricultural expansion and intensification, significant
woodland expansion and when air pollution abatement strategies were
being developed and implemented. Land use and environmental
conditions (e.g. air pollution) have changed markedly since that
programme of sampling. Re-sampling now provides a unique opportunity
to quantify the impacts of those changes on the characteristics of
soils, thus providing evidence from which to develop policies to
protect our soils as we enter a further period of extensive change,
both in land use and the environment.
A range of new techniques and methods are being considered; the NSIS
provides the widest possible range of soils upon which to test them
fully. Soils selected from the NSIS are therefore essential to carry
out the most rigorous evaluation of these new methods.
It describes the soil environment of Scotland, and its relationship
to above-ground plant communities, thus allowing examination of the
biogeographical associations of microbes, vegetation and climate.
It is a well documented and consistent dataset, described, sampled
and analysed using consistent techniques, guidelines and methods.
The 10 km x 10 km
intersections of the National grid were sampled, producing
approximately 3,000 samples from across the country. These samples
have been analysed for their physical and chemical properties. This
resource, forms part of Scotland’s National Soil Archive (which
contains over 40,000 samples), and is held at the Macaulay Institute,
in Aberdeen. In a sense, this archive can be considered to be a soil
museum, and like all items housed in a museum they are irreplaceable.
As for all data, that for
soils will age and a partial updating of the NSIS is currently under
way, which will allow recently developed analytical techniques to be
applied to fill gaps in the dataset and also help chart recent
environmental changes.
Applications of soils
data and maps Although environmental
data, including those on soils are invaluable in their own right, and
represent a record of our natural capital, the application of these
data to address a range of land use, environmental and ecological
issues is probably what interests a wide and diverse range of
stakeholders.
One of the first
applications is that of the Land Capability for Agriculture (LCA),
which was developed by the Macaulay Institute to describe the
agricultural potential of land based on the degree of limitation
imposed by its biophysical properties. It is a seven class system
with Class 1 having the fewest limitations to agricultural
exploitation, and Class 7 having little agricultural value. It is
based, primarily, on climate, a number of soil properties, (for
example depth and stoniness), wetness, erosion risk and slope. Also
included is the overall pattern, i.e. variability, of the soil
properties and, in one of the classes (Class 6), vegetation cover is
also taken into account. The system therefore does not rely on soils
data alone but they do form a key constituent.
A
similar system has been developed for forestry but with different
soil parameters reflecting the differences in growth requirements
between agricultural crops and tree species. The LCA maps,
although now in digital format, were produced by field based
evaluation methods but can now be automated within a Geographic
Information System, which will allow a range of scenarios of change
in climate and soil properties to be explored.
A wide range of other
applications have capitalised on this valuable map and database
resource. Theses include:
The development of a
hydrological classification of soils (Hydrology of Soil Types HOST).
This in turn has been used in a wide range of applications, in
particular those that seek to determine pollutant transport through
soils and into water bodies.
A soil erosion risk
classification which includes the integration of a few key soil
attributes that are known to influence the physical movement of
soil. Again there can be serious down-stream effects on water
quality.
A model of native
woodlands, which is a rule-based system that seeks to identify the
best sites for new native woodlands based on soil conditions
The assessment of
the capacity of different soils to bind pollutants and prevent their
release to plants, water and air.
Many of these more recent
applications have an ecological or environmental emphasis, reflecting
the change in research focus from primary plant production to the
wider multi-functional dimensions of soil.
Climate change
The
land and forestry sectors account for 20% of carbon dioxide emissions
in Scotland, which is second only to that of power generation. This
means that soils play a pivotal role in regulating, adapting and
mitigating future climate change as they are a sink and a source of
climate greenhouse gases.
Soils
in different parts of the globe will respond differently to climate
change. Climate may cause direct changes in soil properties that
feedback to climate change such as, higher carbon turnover rates or
nitrous oxide emissions when land-use is changed.
Advances on a number of fronts - through the merging and testing of
the available national databases, and the spatial analysis of their
characteristics; the development of soil analysis and protocols and
their modification for applicability in court; coupled with various
re-sampling initiatives – means that the UK should be an excellent
place to test the application of soil to forensic investigations, in
both criminal and environmental case work.
Other
impacts are indirect. Freely drained soils may become droughtier
leading to lower crop yields and increased vulnerability to wind
erosion. In contrast, other soils may become wetter, resulting in
shorter access periods for farm/forest operations and grazing.
The
Macaulay Institute is currently working on updating the Land
Capability for Agriculture maps with an aim to determine where and
how agricultural activity could change if scenarios of climate change
actually manifest themselves. It may be that Scotland’s climate
might change and become more favourable for a wider range of crops,
but it does not necessarily mean that those crops would be more
productive. Indeed, yields might decline due to a lack of available
moisture in the soil. How soils respond to climate change is a key
element affecting future land use.
Comparing
modern soils with historic data from soil archives is proving vital
in monitoring the status, impacts and response to climate change of
key processes such as organic matter loss or carbon sequestration.
This has been done in England and Wales where large declines in soil
carbon have been recorded particularly on relatively unmanaged soils
with high carbon contents; this was counter to perceived wisdom in
the soil science community. If this finding was extrapolated to
Scotland, where highly organic soils are much more extensive, the
consequences for our valuable habitats like blanket bog and heather
moorland would be very serious. Our current resampling of the NSIS
will go some way to answering this question.
Soil
Forensics Perhaps the most exciting (and high-profile) recent application of
both the existing and new databases is within the field of soil
forensics. Today there is general recognition that trace evidence
(fibres/fluids/particles) found at a scene of crime can be
instrumental in providing criminal intelligence to police
investigations. Soil is a complex matrix composed of mineral grains,
organic material, and living and decomposing organisms. The
proportions and characteristics of the mineral, organic and
biological components of soil vary, often in a unique manner.
Underlying parent material, land-use/vegetation, and climate have
important influences on soil composition.
Soil particles readily
adhere to, and transfer from clothing, shoes, vehicles or tools, and
can therefore be treated as trace evidence, potentially linking
suspects to, or eliminating them from, a crime scene. Traditional
methods applied to soil forensics have proven themselves in courts of
law, through the judgment and testimony of an expert witness, and
include visual comparison of colour, particle mineralogy and
palynology (identification of pollen and spores).
With recent advances in
analytical methodology, soil components can be separated and
characterised at an increasing level of detail, and on an
increasingly small size of sample. Recent years have seen significant
analytical advances in profiling methods that can be applied to soil.
For example Infa-Red radiation can be used to provide a general
profile of soil chemistry; XRDP can provide a detailed fingerprint of
the mineral components of soil, while advances in molecular microbial
methods can be applied to fingerprint the biological component of
soil. Research is currently underway to test such fingerprinting
methods against conventional methods, to link the data to the
available databases and to determine their likely applicability and
use, depending upon the size, condition of sample and other case
specific information.
An
EPSRC-funded project entitled SoilFit (www.macaulay.ac.uk/forensics),
run from the Macaulay Institute, in collaboration with NSRI and
DARDNI, is using a suite of measurements to characterise soil samples
from across the UK. The resulting database will include detailed
information on a range of outputs including colour, particle size
analysis, mineralogy, general chemical fingerprint, microbial
community characterisation, wax biomarkers, pollen profiling,
elemental analyses; major and trace minerals, and isotopes.
One crucial component of the SoilFit projects’ approach to soil as
a forensic tool, is the development of a set of reference soils and
databases. These databases will enable the estimation of the
probability of obtaining accurate soil matches. Creating such a
reference database offers great potential in effectively and
efficiently applying soil forensic methods. Combining formal
statistical analysis with highly specific, polyphasic soil
fingerprinting methods will make soil analysis a more effective tool
for routine forensic work, thus considerably extending its
applicability.
Soil
Forensics- reduction of search areas
Based upon
the matching of soil properties from case evidence, with soil maps
and spatial databases, potential target areas for search can be
identified. The onus is then on the soil forensic research team to
obtain the crucial link between the legal investigation area and the
geo-morphological evidence. Non-invasive soil property monitoring,
such as through airborne or terrestrial remote sensing, allows a
potentially rapid search of areas of interest.
The use of Ground Penetrating Radar (GPR) can assist police and law
enforcement investigation teams in forensic searches, enabling the
rapid, non-destructive, searching of large areas for buried objects,
hides and caches, and the detection of cavities both in the ground
and in structures. This greatly improves search efficiency and
reduces unnecessary excavation operations.
Linking
descriptions of the soil characteristics of a field sample, from
analytical and non-invasive sources, with the content of spatial
databases of soils and vegetation enables areas of search to be
geographically targeted. This can be done, for example, by
identifying sites with a combination of soil and vegetation
characteristics derived from analysis of evidence. Other geographic
datasets (e.g. data on transport routes and population centres) can
then be used in combination with those of soils and vegetation to
explore hypotheses for the targeting of areas of search.
Urban surface soils A coordinated network of
related ‘projects is being developed, in partnership with the
Robert Gordon University, Aberdeen, and based at a range of
collaborating UK Universities. These projects are known as the Soil
Forensics University Network (SoilFUN). The
network draws together academics from a number of Universities in the
UK who, through the use of student projects, will generate analytical
data on a variety of soils in their urban areas. This coordinated
approach uses a high degree of similarity in experimental design and
quality control between the participating Universities.
Of particular forensic
interest are the soil samples taken from surface layers in urban
areas. The aim of SoilFUN is to broaden the knowledge of the urban
soil environment. Specifically, it is hoped to address between
city and within city discrimination of common urban
land-use vegetation (LUV) classes. Each individual project targets
four (LUV) types, each of which is represented at four sites across
the urban area. Four replicate samples are taken at each site. The
database will include replicate analytical information from the
following urban location types: semi-natural deciduous wooded areas,
managed flowerbeds, and man-made disturbed roadside lay-bys.
A number of parameters
have been selected as having the potential to allow discrimination of
surface layers of urban soils. These parameters have been selected as
requiring chemical instrumentation that is readily available in
university departments and is accessible to undergraduate and
postgraduate students for use in project work. These include; visual
inspection using a stereomicroscope, colour determination using
spectrophotometer/Munsell colour charts, organic matter content using
muffle furnace, biomarkers using GC-MS, and chemical profiling using
ATR-FTIR.
The coordinated approach
to the sampling and analysis will deliver a robust database of urban
soils information from across the UK.
Future The agriculturally focused soil mapping and
archiving programmes of the last 60 years are now finding a new lease
of life combating some of today’s most pressing problems.
Advances on a number of fronts - through the merging and testing of
the available national databases, and the spatial analysis of their
characteristics; the development of soil analysis and protocols and
their modification for applicability in court; coupled with various
re-sampling initiatives – means that the UK should be an excellent
place to test the application of soil to forensic investigations, in
both criminal and environmental case work.
by Lorna Dawson, David
Miller and Willie Towers - Macaulay
Institute, Aberdeen, UK
For many years, improving
agricultural production was the main goal of soil science. As part of
this, a number of country-wide soil mapping programmes took place
across Europe during the 20th Century, which also resulted
in the creation of several national soil databases. Today, the
importance of these data, complemented in some countries with
irreplaceable archives, goes far beyond agriculture. They are proving
to be an invaluable resource for a wide range of applications - from
measuring the effects of climate change, monitoring environmental
pollution and atmospheric deposition, to helping solve serious
crimes.
