Appendix C. Additional discussion on soil sterilization.
The potential alteration in soil structure, nutrient levels, and soil fauna from soil sterilization (Eno and Popenoe 1963, Bradford et al. 2002), is an unlikely explanation for the findings in experiment 1. We found no evidence that soil sterilization in this study resulted in a bias among the treatments. The untreated field soil (with the soil microbial and faunal communities present) responded nearly identically to the sterile irradiated soil with added pathogens (Fig. 1), suggesting that soil microbes reduced productivity at low levels of diversity, not an artifact of the soil sterilization process. The slightly higher level of productivity in untreated field soils compared to the pathogen-augmented soil may have been attributable to AMF, soil fauna, saprobes, or some combination of these factors.
Bradford, M. A., T. H. Jones, R. D. Bardgett, H. I. J. Black, B. Boag, M. Bonkowski, R. Cook, T. Eggers, A. C. Gange, S. J. Grayston, E. Kandeler, A. E. McCaig, J. Newington, J. I. Prosser, H. Setala, P. L. Staddon, G. M. Tordoff, D. Tscherko, and J. H. Lawton. 2002. Impacts of soil faunal community composition on model grassland ecosystems. Science 298:615618.Eno, C. F., and H. Popenoe. 1963. The effect of gamma radiation on the availability of nitrogen and phosphorus in soil. Soil Sci. Soc. Am. J. 27:299301.