Please note: This research Programme is no longer active
Soil Biodiversity Programme aimed to achieve simultaneously:
understanding of biological diversity of the soil biota
(embracing all abundant
taxa, not just those normally considered tractable),
the functional roles played by soil organisms in key ecological
million was allocated by the Natural
Environment Research Council
(NERC) for research and necessary support services. The Programme was
closely integrated, to give insights of wider generality than the chosen
ecosystem, an upland grassland at Sourhope, near Kelso, Scotland.
Research was funded in
two main phases, the first starting in 1998. The second phase ran
from 2001 - 2005. Details of current research projects and
outputs can be found in the sections below.
The objectives of the Soil Biodiversity Programme
To quantify the taxonomic and metabolic
diversity of key groups in the soil biota in a single ecosystem, sufficient to provide a
sure basis for an experimental programme to determine the role of diversity in ecosystem
To extend taxonomic understanding of the
soil biota, especially by using isolation and molecular techniques to examine hitherto
poorly characterised groups.
To characterise the roles played by all
major groups within the soil biota (including rootmicrobe associations) in
ecologically important processes in the carbon and nitrogen cycles in soil, including the
development of carbon sinks, so as to determine the pathways and rates of movement of
carbon through components of the soil foodweb.
To determine (both experimentally and by
comparison of contrasting sites) the extent to which depauperation of the soil biota may
reduce their ability to perform essential ecosystem services, including the ability to
cope with anthropogenic inputs.
To conduct parallel manipulations of major
taxonomic groups of soil biota under controlled conditions.
To determine the extent to which indicators
of soil biodiversity are measures of the soil ecosystem resilience of relevance to land
It was intended that research projects
used common experimental and identification protocols, allowing a robust test of the
generality of the findings.
A central question in ecology is whether there is a necessary link between biological
diversity and ecosystem function. Biogeochemical cycles are among the most fundamental of
the functions performed in ecosystems, and many critical processes in these cycles (e.g.
decomposition, nitrogen transformations, trace gas generation) occur in soil and are
mediated by soil organisms. The role of these organisms in biophysical processes (e.g.
hydrological cycling, energy balances) is unclear but almost certainly profound. Soil
communities are currently exposed to a wide range of impacts, including erosion,
agricultural intensification, and the deposition of acidic and nitrogenous pollutants,
with poorly documented effects on diversity of the soil biota, and virtually unknown
effects on ecosystem processes.
ROLE OF SOIL
Soil organisms also control the magnitude and chemical nature of the globally significant
C and N fluxes from soils. The role of some bacteria in these transformations is well
established, but rates and pathways of soil biological processes are typically studied as
functions of environmental rather than biological variables. The roles played by most
groups of soil organisms is very poorly known, although a general theoretical and
conceptual framework is emerging. Experimental demonstrations of the importance of
faunal-microbial interactions are rarely performed in a context where their significance
to ecosystem-level processes can be inferred.
Basic knowledge of the diversity of the soil biota is rudimentary. Molecular
techniques confirm that the undescribed diversity is large, and that this
genetic diversity can be linked to process studies if it can be
characterised using molecular probes and taxa assigned to functional groups.
Molecular techniques now offer an unique way forward when combined with
other new or advancing technologies (e.g. NMR, confocal microscopy, GC-MS)
to frame answerable questions about the diversity/function relationships in
The Programme combined detailed taxonomic description with an experimental approach
designed to utilise that description to test hypotheses about the functional role of
biodiversity. It was based on an intensive study of a single site. Diluting the effort
over a range of sites would have precluded proper investigation of functional links between
taxonomic diversity and function, and intensive studies at a range of sites would
The research focussed on a grassland system at the Sourhope Research Station in
the Cheviot Hills, which is part of the UK Environmental Change Network and the most
thoroughly studied site in the SOAEFD MicroNet programme. Sourhope has extensive areas of
upland grassland (Agrostis-Festuca; National Vegetation Classification U4), for
which data on microbial diversity were already becoming available.
The Programme also had access to the Ecotron facility, at the Centre for Population
Biology (CPB) Imperial College, in which a simplified grassland ecosytem was created
with communities of varying diversity to defined taxonomic specifications. A key part of
the field and Ecotron-based parts of the Programme involved the introduction of a
large pulse of 13C to the grassland ecosystem and monitoring progress of this
signal through the soil ecosystem which was manipulated so as to alter its structure.
The 13C pulse was added to the Ecotron system early in the life of the
Programme and results from these mesocosm studies were used to generate predictions
about expected responses in the field. A pulse was added in the field following a
period of characterisation and protocol development.
A series of manipulation experiments were applied to large plots at Sourhope and used
to test a number of hypotheses, for example:
Reducing the diversity of
the soil community will increase the residence time of carbon in soil pools, but that
surviving taxa will react and compensate for such reductions.
Specific taxa (benchmark
organisms or groups) play key roles in this process.
Rates of carbon cycling are
less sensitive to the quality of the carbon inputs when the diversity of the soil
community is high.
Taxonomic and functional
diversity of the soil community is reduced by physical and chemical perturbations.
Resilience of the ecosystem
will be greatest when diversity is high.
Before the Programme began, the following field manipulations were
Changes in carbon and
nitrogen inputs by removal of grass litter (following mowing) from all plots and its
addition to other plots, or by selective grazing.
Application of a biocide,
which would remove or reduce selected taxa. Although the limitations of this technique are
recognised, it has been used successfully to determine changes in soil foodwebs and
ecosystem properties. An Ecotron experiment would create ecosystems that mirror the
effects of these field treatments, by omitting specific taxa from the
artificial communities in a replicated design. If possible, soil fungi
could also be manipulated in this way.
Application of a pollutant
(e.g. a heavy metal) which would affect most taxa indiscriminately and also provide a
further signal whose progress through the foodweb can be monitored; identical pollutants
can be added to mesocosm communities.
Some plots will receive a
short perturbation and the recovery studied to allow some assessment of resilience.
Additional manipulations are possible within this design, including those aimed at
measuring the effect of global change factors (temperature, uv penetration) or land-use
(change from grassland to arable), and ancillary studies such as an intensive study of
There will be a need for
laboratory microcosm work to characterise the metabolic and functional capabilities and
environmental tolerance ranges of key species and groups identified from the field