Resilience of the rhizosphere to anthropogenic disturbance

The rhizosphere is a dominant site of microbial metabolism in soil and whereas it can be shown that anthropogenic disturbances can influence this metabolism, the impact of these disturbances on biodiversity is rather difficult to determine at the species level. This is in part because no more than 10% of the microbial species are culturable, and in part because there is very poor precision in plate counting, usually requiring a change of 300-500% to be significant. We have therefore used a functional approach. The `ecophysiological index' is based on r or K strategy of the organisms being counted. Also, enzyme families, microbial biomass, microbe/microbe and microbe/fauna interactions have been determined, along with nutrient uptake measurements. The techniques have been applied to determine the effects of disturbances created by the introduction of GM plants and microorganisms to soil, these effects being small compared with those caused by time-honoured practices such as crop rotation and ploughing. Toxicity from industrial influences (e.g. cyanide) can be remediated by rhizosphere microorganisms.