Highlighting Complex Systems Phenomena For Soil Modeling In The Anthropocene

Ecosystem management is integral to future soil states, yet anthropogenic drivers remain a major source of uncertainty in ecosystem models. Systems or complexity theory, based on examples from other fields, can offer more generalized understanding, as well as analytical tools that may help improve the robustness and lower uncertainty in existing model structures, and in turn also parameter space. A key broad assumption is that soil variables are never in equilibrium, suggesting that over time, soils reflect adaptations to persistent positive feedbacks. This synthetic study asked broadly: which soil functions can be better understood by analyzing through a complex systems lens, and how? Reviews and concepts from non-linear dynamical systems in theoretical ecology and soil sciences were synthesized into a perspective on areas for further study may help improve the robustness of soil models under the uncertainty of human acitivities and management.

Several key aspects of how soils function were organized and identified as notable for resembling phenomena observed in other complex systems, supporting conceptual shifts for future study, namely: 1) reversibility of organo-mineral associations, 2) aggregate- and pore hierarchy and dynamics, 3) persistent wet-dry cycles, 4) multi-year gas flux rates and nutrient availability, 5) higher-order microbial community and predator-prey interactions, 6) cumulative legacy land use history, and 7) social management interactions/cooperation. Each of these aspects was detailed on how it may contribute useful analytical tools, metrics, and/or frameworks that help integrate the uncertainties in future soil states, ranging from micro- to regional scales, including those indirectly affected by human activities and management decisions. Overall this study points to potential future transdisciplinary collaborations with social and political scientists to better integrate longer-term anthropogenic drivers of soil processes, in line with recent studies in anthropedology and biogeosociochemistry, and expanding from nutrient cycles to include additional facets of soils like structural dynamics and microbial and food web ecology.