Soil Biodiversity Programme background and objectives

The objectives of the Soil Biodiversity Programme were:

• 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 processes. 
• 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 root–microbe 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 use management.

It was intended that research projects used common experimental and identification protocols, allowing a robust test of the generality of the findings.

Biodiversity in soil

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 organisms

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.

New techniques

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 soil.

Rationale

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 have been prohibitively expensive.