Multifunctionality of belowground food webs: resource, size and spatial energy channels

Abstract

The belowground compartment of terrestrial ecosystems drives nutrient cycling, the decomposition and stabilisation of organic matter, and supports aboveground life. Belowground consumers create complex food webs that regulate functioning, ensure stability and support biodiversity both below and above ground. However, existing soil food-web reconstructions do not match recently accumulated empirical evidence and there is no comprehensive reproducible approach that accounts for the complex resource, size and spatial structure of food webs in soil. Here I build on generic food-web organization principles and use multifunctional classification of soil protists, invertebrates and vertebrates, to reconstruct "multichannel" food-web across size classes of soil-associated consumers. This reconstruction is based on overlying feeding preference, prey protection, size spectrum and spatial distribution matrices combined with biomasses of trophic guilds to infer weighted trophic interactions. I then use food-web reconstruction, together with assimilation efficiencies, to calculate energy fluxes assuming a steady-state energetic system. Based on energy fluxes, I describe a number of indicators, related to stability, biodiversity and multiple ecosystem-level functions such as herbivory, top-down control, translocation and transformation of organic matter. I illustrate the approach with an empirical example, comparing it with traditional resource-focused soil food-web reconstruction. The multichannel reconstruction can be used to assess trophic multifunctionality (analogous to ecosystem multifunctionality), i.e. simultaneous support of multiple trophic functions by the food-web, and compare it across communities and ecosystems spanning beyond the soil. With further validation and parametrization, my multichannel reconstruction approach provides an effective tool for understanding and analysing soil food webs. I believe that having this tool will inspire more people to comprehensively describe soil communities and belowground-aboveground interactions. Such studies will provide informative indicators for including consumers as active agents in biogeochemical models, not only locally but also on regional and global scales.

Feeding habits and multifunctional classification of soil‐associated consumers from protists to vertebrates

“…However, the most powerful use of this classification is to assess multifunctionality of soil consumer communities via a food-web approach. In an associated conceptual soil foodweb review (Potapov, 2021), this classification and generic predator-prey interaction patterns were used to construct 'multichannel' soil food webs. This food-web model was further combined with energy flux approaches (Barnes et al, 2014(Barnes et al, , 2018 to infer multiple ecosystem functions by consumer communities, for example litter transformation, herbivory and top-down control, and to assess rapid to slow energy channelling and spatial distribution of energy fluxes in soil food webs.…”

Global monitoring of soil animal communities using a common methodology

“…Soil communities will be characterised at each sampling site based on the list of taxonomic and functional groups with data on their abundance, individual body masses, and total biomasses (the tentative list of target groups is given in Table 1). On the one hand, a taxonomic grouping should be detailed enough to make functional inferences as well as a food web reconstruction possible (Brussaard 1998, Briones 2014, Buchkowski & Lindo 2021, Potapov 2021). On the other hand, the grouping should be generic enough to include all major taxa and regions and easy enough to allow the sorting by a general soil ecologist from a mixed community image, i.e.…”

“…We will also compare soil animal communities inside and outside of the protected areas worldwide to evaluate the effect of current conservation practices on soil animal communities. To analyse the animal data, we will use different approaches, such as path analysis (Eisenhauer et al 2015), geospatial modelling (van den Hoogen et al 94 (1) 2022 2021), food-web reconstruction and modelling (de Vries et al 2013, Potapov 2021, and energy flux approaches (Barnes et al 2018, Jochum et al 2021. We also plan to link collected animal data with multiple functional traits to assess global variation in the functional diversity of soil animal communities (Pey et al 2014, Brousseau et al 2018 and work on integration of our results in suggested animal-based biogeochemical models (Chertov et al 2017, Deckmyn et al 2020, Flores et al 2021.…”

“…A comprehensive community-level assessment will make it possible to reconstruct soil food webs and infer energy fluxes to describe biotic controls, trophic functioning, and stability patterns of soil biodiversity. Food webs is a particularly powerful approach to link soil biodiversity to both ecosystem functioning and environmental drivers (de Vries et al 2013, Potapov 2021. Existing global extrapolations of soil biodiversity remain poorly linked to soil functions with only 0.3% of soil ecological studies simultaneously assessing soil biodiversity and functions (Guerra et al 2020).…”

“…Abundances and body sizes of taxonomic groups are estimated by the Central team using manual image annotations and a trained image analysis algorithm(Schneider et al 2021). Biomasses and energy fluxes are estimated using allometric regressions and food-web reconstruction approaches(Ehnes et al 2011, Sohlström et al 2018, Jochum et al 2021, Potapov 2021) and used in statistical analyses and modelling.…”