A call for international soil experiment networks for studying, predicting, and managing global change impacts

• Published in: SOIL
• Main Authors: Torn, M. S., Chabbi, A., Crill, P., Hanson, P. J., Janssens, I. A., Luo, Y., Pries, C. H., Rumpel, C., Schmidt, M. W. I., Six, J., Schrumpf, M., Zhu, B.
• Language: unknown
• Published: 2023
• Subjects: 54 ENVIRONMENTAL SCIENCES; 58 GEOSCIENCES; Arctic
• Online Access: http://www.osti.gov/servlets/purl/1286979; https://www.osti.gov/biblio/1286979; https://doi.org/10.5194/soil-1-575-2015

The soil profile encompasses a remarkably large range of biogeochemical conditions, processes, and fluxes. For example, in most soils the turnover time of soil organic carbon (SOC) varies more between the soil surface and 1m deep than between surface soils in the tropics vs. the Arctic (Torn et al., 2009). Moreover, radiocarbon observations in different soil types show that SOC decomposition rates decrease with depth, with residence times of years to decades at the soil surface to over 10 000 years at 1m deep (e.g., Torn et al., 2002). There are many competing hypotheses for this steep decline in SOC turnover with depth. They can be grouped loosely into physical–chemical accessibility, energetic limits to microbial activity, microclimate and pH, and physical disconnect between decomposers and substrate. While all of these mechanisms control deep SOC cycling, data are lacking for unraveling their relative importance in different soils under different environmental conditions. However, critical knowledge for predicting soil responses to global change, because fairly rapid loss (or gain) of old and/or deep SOC stocks is possible and more than 80% of the world’s SOC is found below 20 cm depth (Jobbágy and Jackson, 2000). Currently, the soil modules within Earth system models are parameterized for surface soil and lack mechanisms important for stabilization and losses of deep SOC. We, therefore, suggest that a critical challenge is to achieve process-level understanding at the global level and the ability to predict whether, and how, the large stores of deep, old SOC are stabilized and lost under global change scenarios.