Out of the dark: Using energy flux to connect above- and belowground communities and ecosystem functioning

Soil ecosystems are both particularly important to humans and vulnerable to human-made global change. Here, we identify some key aspects of soil community and ecosystem research that need to be more widely studied to understand soil responses to global change and enable us to efficiently protect them. This perspective integrates multiple taxa and trophic levels, combines structural community variables with ecosystem processes, and considers multiple energy channels rather than focusing on only bacterial, fungal, or plant-derived resources. Moreover, it enables implementing the claim that terrestrial ecosystem research should more widely adopt an integrative view of above-belowground processes. Having identified these key areas requiring higher attention, we suggest a wider application of the food-web energetics approach to calculating energy flux as a suitable and very powerful tool to simultaneously integrate these aspects. The approach combines food-web and metabolic theory to quantify energy flux through trophic networks as a universal currency of multitrophic ecosystem functioning. In addition to whole-community metrics, it allows for quantifying various important processes by summing up the flux out of autotrophs, detritus, or animals to their respective consumers. This includes the assessment of processes that are otherwise hard to quantify, such as belowground herbivory or predation. The calculation requires data on the focal community and its metabolic demand, trophic interactions, feeding preferences and assimilation efficiency, some of which can be measured, whereas other components can be inferred from readily available literature resources. We outline how novel, high-throughput methods, such as metabarcoding, can be combined with the energy-flux approach to improve our understanding of soil ecosystem structure and functioning. We hope that our article motivates fellow soil researchers to adopt energy-flux approaches for their community data and support the further development of this promising approach for soil community and ecosystem science. Highlights Multitrophic interactions bridge the structure and functioning of soil ecosystems. An integrated ecosystem perspective requires the quantification of the main energy channels in soil. Linking above- and belowground compartments provides deeper insights into whole-ecosystem processes. Quantifying energy flux through above-belowground systems enables those insights.

Automated summary

This paper emphasizes the importance of multitrophic interactions in bridging the structure and functioning of soil ecosystems. Quantifying the main energy channels in soil is essential for gaining a deeper insight into whole-ecosystem processes, while linking above- and belowground compartments provides valuable insights into soil ecosystem functioning. Calculating energy flux through above-belowground systems enables a better understanding of soil ecosystem dynamics.