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

The biomass of invertebrate root feeders in pastures can be large, for example it has been estimated that the population of leatherjackets (Tipula spp.) can exceed that of grazing domestic livestock. The removal of and/or damage to root material from a growing plant and the effect which this may have both on the plant itself and on the rhizosphere community has been the subject of few investigations.
As part of the NERC Soil Biodiversity Programme (http://mwnta.nmw.ac.uk/soilbio) we are investigating the impact of invertebrate root herbivory on rhizosphere carbon flow and soil microbial communities. Agrostis capillaris, Lolium perenne and Trifolium repens were grown in sand in microcosms which enabled collection of rhizodeposits, in the presence and absence of insect and nematode root herbivores. Invertebrate root herbivory resulted in increased carbon release to the rhizosphere. The exudates were applied to soil and changes in microbial community structure and function measured using community level physiological profiling (CLPP) and phospholipid fatty acid (PLFA) profiling. The importance of understanding soil organism interactions and the consequences for nutrient cycling and vegetation dynamics are discussed.