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Understanding global environmental change is a major challenge for 21st-century science; monitoring and understanding national soil change is no exception. National scale monitoring results for soil pH, carbon, and total nitrogen status for Great Britain show that soil change is occurring on anthropogenic time scales and that environmental protection legislation is an important tool for reversing potential detrimental impacts. Understanding “soil change” at the national scale, in addition to soil status, is a key challenge for national scale soil monitoring programs and is essential if more sustainable use of this finite resource is to be achieved. We present results from the first national scale survey of soil change to be reported three times within Europe and perhaps globally, covering a 30-yr time span. Countryside Survey is an integrated national monitoring program that makes measurements of vegetation; topsoil physical, chemical, and biological characteristics (0–15 cm); water quality; and land use across Great Britain (GB), thus recognizing their interdependence. Here we report on change in fundamental soil chemical characteristics. Soil pH and loss on ignition (LOI) were measured in 1978, 1998, and 2007 and soil total nitrogen (total N) concentration and C/N ratio in 1998 and 2007. Bulk density was measured in 2007. Mean soil pH increased significantly in less acidic soils from 1978 through 1998 to 2007. Mean pH increased significantly in more acidic, organic-rich soils from 1978 to 1998 but not between 1998 and 2007, indicating spatial trends in both sulfur deposition reductions and soil sensitivity. There was a small increase (8%) in GB topsoil C concentration (calculated from LOI) between 1978 and 1998, a small decrease (6.5%) between 1998 and 2007, and no significant overall change between 1978 and 2007. The unresolved difference between these results and those from the National Soil Inventory of England and Wales that reported wide-scale large decreases

The DyDOC model was used to simulate the soil carbon cycle of a deciduous forest at the Oak Ridge Reservation (Tennessee, USA). The model application relied on extensive data from the Enriched Background Isotope Study (EBIS), which exploited a short-term local atmospheric enrichment of radiocarbon to establish a large-scale manipulation experiment with different inputs of 14C from both above-ground and below-ground litter. The model was first fitted to hydrological data, then observed pools and fluxes of carbon and 14C data were used to fit parameters describing metabolic transformations of soil organic matter (SOM) components and the transport and sorption of dissolved organic matter (DOM). This produced a detailed quantitative description of soil C cycling in the three horizons (O, A, B) of the soil profile. According to the parameterised model, SOM turnover within the thin O-horizon rapidly produces DOM (46 gC m-2 a-1), which is predominantly hydrophobic. This DOM is nearly all adsorbed in the A- and B-horizons, and while most is mineralised relatively quickly, 11 gC m-2 a-1 undergoes a “maturing” reaction, producing mineral-associated stable SOM pools with mean residence times of 100-200 years. Only a small flux (~ 1 gC m-2 a-1) of hydrophilic DOM leaves the B-horizon. The SOM not associated with mineral matter is assumed to be derived from root litter, and turns over quite quickly (mean residence time 20-30 years). Although DyDOC was successfully fitted to C pools, annual fluxes and 14C data, it accounted less well for short-term variations in DOC concentrations.

This report presents results from a field assessment of a limited suite of potential biological indicators of soil quality to investigate their suitability for national-scale soil monitoring.

This presentation outlines the final results from the UK Defra SQID project which identified and piloted a suite of biological indicators of soil quality for deployment in national-scale soil monitoring programmes to meet a range of UK policy objectives. The indicators were selected to provide information on the soil biological processes which underpin soil function and therefore support ecosystem services. A semiquantitative framework was used to systematically capture the wealth of information in the literature and from expert knowledge on potential indicators of soil quality with a total of 183 indicators assessed. Six soil biological methods have now been piloted in the UK using two complementary field approaches. These six reflect the genotypic, phenotypic and functional characteristics of soil biodiversity. Here we review the results from the two field approaches, the first to assess the temporal sensitivity of biological indicators to key environmental pressures across a 12 month window and the second to asses the ability of biological indicators to discriminate between different habitats. We discuss the relative performance of the indicators and how these were prioritised for national-scale soil monitoring and finally, how this process has revealed new insights into the distribution and characteristics of soil biological properties within UK soils and habitats.

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 inval