A recent review of indicators of soil quality

This showed that:

• Soil indicators such as pH, organic matter content and total nitrogen can only be used effectively in sustainable forestry management if threshold values are identified
• Thresholds for some indicators have been proposed in Europe – for example Ca:Al and base cation (BC):Al molar ratios – but these have received considerable criticism
• There is a need to continue to research these soil quality indicators (Ca:Al and BC:Al molar ratios) since they have been used as criteria in setting threshold pollutant inputs, or critical loads, on which pollution abatement strategies have been based
• There is a lack of biological soil quality indicators.

Principal requirements for soil indicators

These are:

• To be sensitive to human-induced changes to the environment
• To be simple and cost effective to measure, and applicable to the majority of soil monitoring networks
• To indicate responses that can be distinguished from natural variability
• To provide both diagnostic and prognostic information.

Future research

In collaboration with Reading University Soil Science Department and the Environmental Microbiology & Ecology Research Group (EMERGE) at Exeter University this will:

• Evaluate soil indicator thresholds based on relationships between soil and tree responses
• Investigate the use of tree fine roots and mycorrhizae as indicators
• Evaluate biological indicators of soil function including respiration, macrofauna distribution, microbial biomass, microbial diversity, community and function and potential N mineralisation.

In addition, research with the Norwegian Forest Research Institute (Skogforsk) will use long-term soil monitoring data to test whether soil indicators can identify trends that can be useful for sustainable forest management.