Phil Murray, Roger Cook, Sue Grayston, Amy Treonis, Lorna Dawson & Alan Gange

The effect of defoliation on the uptake, efflux, translocation and partitioning of nutrients in plants has been studied widely. 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. The perennial nature of the grass crop ensures that there is always some, and usually an abundance of vegetation and root material present. Consequently, large numbers of invertebrates, many of which are recognised as pests, accumulate. Recent work has demonstrated that below ground herbivory can result in qualitative and quantitative changes in root exudation from plants that can impact on soil microbial diversity and functioning. We know something of the insect and nematode species that cause direct damage to agricultural grassland, but the potential impact of root feeding by invertebrates on microbial driven nutrient cycling has not been evaluated. The current work is part of a UK national project to determine the role of soil biodiversity on ecosystem functioning at an upland grassland site at Sourhope in Scotland.

The diversity of rhizophagous species is being monitored over a three-year period. on plots under various management regimes. All plots are cut 5 times per annum. There are 3 main-plot treatments each with a ryegrass reseed sub-plot receiving the same treatment; a control treatment, a fertilizer treatment (receiving nitrogen and lime) and a pesticide treatment (receiving the equivalent of 1.5l ha-1 of Chlorpyrifos after each cut).

Initial results have revealed the presence macro root herbivores, including Tipulid, Bibionid and Scarabaeid larvae in addition to a number of species of plant parasitic nematodes, suggesting that macro root herbivores are likely to form a significant component of the soil fauna at this upland grassland site.