Linking soil organisms within food webs to ecosystem functioning and environmental change.
Agronomists, ecologists, ecosystem scientists, and various other researchers are recognizing the value of studying responses of soil biota to environmental perturbations because of their functional roles in ecosystem processes and varying sensitivities to environmental perturbations. In this chapter, I provide a descriptive overview of trophic interactions in soil and selected examples of current research on soil biotic responses to human-associated disturbance [biodiversity loss, invasive species, climate change, and genetically modified (GM) crops]. In many cases, researchers generally use population estimates of functional groups as a surrogate for food web interactions and, from these, infer that responses could cascade through food webs to impact ecosystem functioning. I then review alternative approaches to monitoring soil food web dynamics, approaches that focus on estimating the emergent properties of food webs themselves. Because these emergent properties are directly linked to nutrient cycling and energy flow, they should provide a more robust indication of ecosystem functioning in response to environmental perturbations. The first, nematode faunal analysis, is an empirical approach that utilizes a subset of soil organisms representing multiple functional groups and incorporates information regarding organism life history to estimate emergent properties of the existing soil food web, such as productivity and sensitivity to disturbance. The second is a modelling approach that attempts to predict how localized changes within a food web will influence the overall stability and productivity of the food web. Finally, I address some shortcomings in our current understanding of soil food web structure and resolution, and promising avenues for addressing these shortcomings.