The changing global carbon cycle: linking plant–soil carbon dynamics to global consequences

Background

This essay review explores how plant–soil interactions shape the global carbon (C) cycle and influence climate feedbacks. The authors note that most current climate–carbon models still rely on the Woodwell–Whittaker model (1968), which simplifies ecosystem carbon dynamics as the balance between net primary production (NPP) and heterotrophic respiration (HR). However, rapid changes in climate, land cover, and nutrient cycles have made this traditional framework inadequate. This paper emphasizes that soils, as the largest terrestrial carbon reservoir, play a crucial role in determining the biosphere's response to human-induced Carbon dioxide (CO₂) emissions.

Goals and Methods

The authors aim to redefine ecosystem–climate models by integrating recent advances in soil biogeochemistry and plant–microbial ecology. Rather than conducting new experiments, the authors synthesize findings from numerous studies to identify processes that strongly influence C fluxes but remain underrepresented in global models. They analyze key linkages among C, nitrogen (N), and phosphorus (P) cycles, the effects of temperature, moisture, and microbial activity on decomposition, and the roles of mycorrhizas, root exudates, and microbial community composition in soil carbon storage. The study also introduces the concept of total below-ground carbon flux (TBCF) as a crucial component of carbon sequestration.

Conclusions and Takeaways

The authors conclude that the traditional NPP–HR balance provides a reasonable approximation of carbon fluxes under steady-state conditions but fails under rapid environmental change. They propose expanding climate–carbon models to include: (1) biogeochemical coupling of C and N cycles, (2) non-CO₂ carbon fluxes such as methane and wildfire emissions, and (3) energy and water exchange feedbacks like albedo and evapotranspiration. Understanding these mechanisms is essential for predicting the direction and magnitude of climate feedbacks. This paper advocates for integrating plant–soil–microbe dynamics into Earth system models to enhance the representation of the global carbon cycle and inform effective climate mitigation strategies.