Living in the soil matrix : abiotic factors affecting root herbivores

Root herbivores live in the soil matrix where they are in constant physical contact with their environment and have become behaviourally and physiologically adapted to its abiotic properties. Soil moisture is amongst the most important factors influencing root herbivores, though this is tightly linked with soil temperature. Root herbivores have evolved behavioural (e.g. cell construction and burrowing) and physiological (e.g. cuticular pumps and spiracle valves) mechanisms to prevent desiccation and suffocation. Carbon dioxide (CO2) is higher within the soil than in the air, and hence, root feeders are physiologically adapted to high concentrations. Indirectly, root herbivores can benefit from elevated atmospheric CO2 through stimulation of root growth, though studies are scarce. Similarly, in an agricultural context, fertilisation usually affects root herbivores positively through improved nutritional quality of host plants. Soil texture and structure is critical for root herbivore movement, and compacted soils cause significant mortality. As a consequence, many maternal insects specifically oviposit in soils amenable to offspring movement.