Susan J Grayston, Philip J Murray, Roger Cook, Amanda Currie, Lorna A Dawson, Alan Gange & Amy M Treonis

In upland pastures the importance of soil biota in plant nutrient acquisition is well recognised. However, the roles played by various groups of soil organisms in nutrient transformations are poorly understood and few studies have addressed interactions between them. In grasslands numerous invertebrates, including insect larvae and phytophagic nematodes accumulate. Root herbivory by invertebrates will change rhizosphere carbon flow and is, therefore, likely to have a major impact on soil microbial communities and subsequently nutrient cycling. However, few studies have linked these processes.

One aim of the NERC Soil Biodiversity Programme (http://mwnta.nmw.ac.uk/soilbio) is to increase our understanding of biological diversity and functioning in soil. As part of this programme the diversity of invertebrate root herbivores and their impact on plant biomass and soil microbial communities across a range of managed grasslands is being investigated. Tipula paludosa and 12 plant parasitic nematodes have been identified as the dominant root herbivores at the site. In microcosm experiments larval herbivory had a significant negative effect on grass growth and the soil microbial community structure was altered. The implications of these findings for understanding the effect of root herbivory on microbial communities and the consequences for nutrient cycling and vegetation dynamics are discussed.