This project prioritised thirteen biological indicators of soil quality which showed
high current potential for deployment in a national-scale soil monitoring scheme.
These indicators met a range of scientific and technical criteria that related soil
functions and feasibility within large-scale surveys. The priority indicators with
associated methodologies are:
- Eight soil microbial groups [ammonia oxidisers, denitrifiers, fungi, bacteria,
Archaea, methanogens, methanotrophs and actinomycetes] identified from
TRFLP fingerprinting
- Soil microbial community structure and biomass characterised from PLFA
profiles
- Multiple substrate induced respiration (MSIR) derived by GC or MicrorespTM
- Multi-enzyme profiling via microplate fluorometric assay
- Nematode community structure from Baermann extractions
- Microarthropod community structure from Tullgren dry extractions
The selection process was robust, repeatable and auditable. A structured framework
denoted a 'logical sieve' was developed to support the incorporation and analysis of
a large number of assessments against a wide range of technical and scientific criteria
relevant to national scale soil monitoring. This enabled a consistent synthesis of
available information and the semi-objective assessment of 183 potential biological
indicators identified from the literature. Stakeholder priorities for technical criteria
were identified through consultation, with the UK-SIC and the expert reviewers, and
incorporated into the final prioritisation phase of the logical sieve. The power of this
approach is that it provides a clear audit trail on the decision-making process and
would allow the inclusion of further indicators into the framework.
The process was initially reviewed by experts familiar with biological indicators and
soil monitoring and then assessed at a two-day expert workshop. Comments and
discussions on the relative importance and robustness of potential indicators and
future research priorities proved invaluable to the final selection. As a consequence,
the logical sieve was modified to prioritise biological indicators for all three soil
functions rather than simply biological indicators with the highest universal scores.
The final priority indicators were selected by reviewing the outputs from the logical
sieve. Each priority indicator, with associated method, was assessed for relevance to
ecological services, obvious surrogacy, the range of indicator indices produced and
practicalities of use. Each priority indicator was reviewed and outstanding issues
relating to deployment identified.
Statistical analyses of existing field survey/experimental data for PLFAs, soil
invertebrates and community-level physiological profiling of the soil microbial
community (BIOLOGTM) highlighted generic technical, policy-related and scientific
issues which were considered in the recommendations for a field evaluation of the
priority indicators