Amy Treonis, Sue Grayston & Phil Murray

The effects of root herbivory on soil processes and biota have not been studied extensively outside of the context of plant pathology.  Root grazing by insect larvae is a potentially important rhizosphere interaction affecting substrate quantity, quality, and spatial distribution in soils.  Root grazing by larvae has been shown to increase root exudation, which should have a strong influence on the structure of soil microbial communities.  The impact of feeding by leatherjacket larvae (Tipula paludosa) on rhizosphere carbon flow and microbial communities was investigated in microcosm experiments using soil from an upland grassland in the Cheviot Hills, Scotland.  Microcosms were constructed to allow aseptic plant growth and collection of root exudates.  Bentgrass (Agrostis capillaris), ryegrass (Lolium perenne) and clover (Trifolium repens) were separately grown in microcosms with and without T. paludosa.  Larvae fed on roots, resulting in changes in the collected root exudates. After application of these exudates to soils, changes in the metabolic profiles and structure of the soil microbial communities were assessed using community-level physiological profiling and PLFA.  The relevance of these changes to increasing our understanding of soil biodiversity and function in the rhizosphere are discussed.