Positive rhizosphere priming accelerates carbon release from permafrost soils.

Area of Science:

• Environmental Science
• Soil Science
• Microbiology

Background:

• Thawing permafrost is a major concern for future carbon release.
• Plant roots can stimulate soil microbes, leading to carbon loss (rhizosphere priming).
• Data on rhizosphere priming in permafrost soils is scarce.

Purpose of the Study:

• To provide direct evidence of live plant-induced rhizosphere priming in Arctic and Subarctic permafrost and active-layer soils.
• To quantify the impact of root activity on carbon loss from these soils.
• To assess the persistence of this priming effect in different soil types.

Main Methods:

• Used 13CO2 labeling to track carbon flow from plants to soil.
• Conducted experiments in controlled environments with diverse Canadian Arctic and Subarctic soil types.
• Measured carbon loss stimulated by plant root activity.

Main Results:

• Plant root activity significantly increased carbon loss from previously frozen soils by 31%.
• The rhizosphere priming effect was more persistent in permafrost soils compared to active-layer soils.
• Evidence of positive rhizosphere priming was observed across various soil types.

Conclusions:

• Live plant roots accelerate carbon loss from thawing permafrost soils.
• Permafrost carbon is more vulnerable to rhizosphere priming than previously thought.
• Plant-soil-microbe interactions must be integrated into models of greenhouse gas emissions from thawing permafrost.