Accounting for Root-Driven Priming of Soil Organic Matter Decomposition Can Improve Model Performance
The interactions between plants and soil play a central role in the functioning of terrestrial ecosystems and the global carbon cycle. Most of these interactions take place in the rhizosphere, the zone of soil that surrounds and is directly influenced by plant roots. The rhizosphere priming effect is a key interaction between living roots and associated rhizosphere organisms that has the potential to alter soil organic matter dynamics by stimulating or suppressing decomposition rates. In a review for New Phytologist, a series of modeling exercises explored how the rhizosphere priming effect might result from an evolutionarily stable mutualistic association between plants and rhizosphere microbes, and how the physiological responses of rhizosphere microbes to different types of plant-derived substrates might help to explain the existence of both positive and negative priming effects. Further, the ability of a commonly used ecosystem model to correctly simulate data from the U.S. Department of Energy-sponsored Duke Free-Air CO2 Enrichment (FACE) experiment was significantly improved by including a priming-induced acceleration of soil organic matter decomposition in response to atmospheric CO2 enrichment. A 40% increase over ambient decay rates for one of the model’s soil organic matter pools enabled better predictions of the increases in plant growth and nitrogen uptake as well as the lack of change in soil carbon observed in the elevated CO2 treatment. This model-data-comparison case study demonstrates the potential importance of the rhizosphere priming effect in terrestrial ecosystems and highlights the value of research efforts to enable its mechanistic incorporation into future ecosystem and Earth system models.
Cheng, W., W. J. Parton, M. A. Gonzalez-Meler, R. Phillips, S. Asao, G. G. McNickle, E. Brzostek, and J. D. Jastrow. 2013. “Synthesis and Modeling Perspectives of Rhizosphere Priming,” New Phytologist 201, 31-44. DOI: 10.1111/nph.12440.