SQID: Prioritising biological indicators of soil quality for deployment in a national-scale soil monitoring scheme. Summary report

Abstract

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