Synthesis and modeling perspectives of rhizosphere priming

What is it about?

Interactions between plant roots, microbial organisms and soil properties are integral to nutrient cycling and soil function. However, little is understood about how, in some circumstances, they give rise to the rhizosphere – the narrow region of soil in direct proximity of plant roots – priming effect (RPE), which is essential to soil organic matter turnover. RPE is the stimulation or suppression of organic matter decomposition in the soil. This is caused by live roots or organisms associated with the roots, such as fungi. Decomposition can mobilise otherwise unavailable mineral resources, such as nitrogen, for the plant to use. WHAT DETERMINES LEVELS OF THE RPE? • Plant species attributes, such as root architecture, canopy size and phenology (recurring plant and animal life cycles, particularly in relation to climate) • Soil properties, such as structure, moisture and chemical composition • The physiology and traits of microbial communities HOW DO GLOBAL ENVIRONMENTAL CHANGES AFFECT RPE? Environmental changes can affect RPE significantly, and it appears that RPE itself can outweigh the effects of global change drivers (warming, rising atmospheric CO2 concentration etc.) on soil organic matter decomposition. Therefore, it is essential that RPE processes are included in Earth system models. To do this, many more studies are needed to understand precisely how RPE responds to global change drivers like rising temperature. Including the activity of roots and soil microbes would also likely change how Earth system models simulate carbon and nitrogen cycles.

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