Below-ground herbivory promotes soil nutrient transfer and root growth in grassland

Extremely little is known about the ecosystem-level implications of below-ground herbivory, which often represents the dominant form of consumption of primary productivity. We provide the first empirical evidence that low levels of below-ground herbivory may promote soil nutrient flux and root growth of both host plants and companion plants. Low levels of white clover ( Trifolium repens L.) root infection by clover cyst nematodes ( Heterodera trifolii Goffart) increased root growth by 141% and 219% in the host plant and the uninfected neighbouring grass ( Lolium perenne L.), respectively. Root infection increased the size of the soil microbial biomass in the root zone and the transfer of ¹⁵N from the host plant to soil and the neighbouring grass. These data suggest that low amounts of below-ground herbivory may increase the transfer of plant carbon and nitrogen below-ground, leading to increases in root growth and soil nutrient recycling in grasslands. Presumably, such interactions will influence the competitive interactions between plant species, altering plant community structure in grasslands.