Microbial community structure and functional genes drive soil priming effect following afforestation

Area of Science:

• Soil Science
• Microbiology
• Ecology

Background:

• Afforestation significantly alters soil organic carbon (SOC) decomposition through the priming effect, driven by plant carbon inputs.
• Soil microbes play a critical role in regulating the magnitude and direction of the priming effect, influencing soil carbon dynamics.

Purpose of the Study:

• To investigate the impact of afforestation chronosequence on soil microbial communities and the priming effect.
• To identify the microbial drivers and functional genes associated with soil organic carbon priming during *Robinia pseudoacacia* afforestation.

Main Methods:

• Metagenomic sequencing and 13C-glucose labeling were employed to analyze microbial communities and priming effects.
• A chronosequence of *Robinia pseudoacacia* stands (14, 20, 30, and 45 years) on the Loess Plateau, China, with adjacent farmland as control, was studied.

Main Results:

• The cumulative priming effect initially increased, peaking in the 20-year-old stand, then declined with afforestation age.
• Priming effect was significantly correlated with microbial community structure (fungal-to-bacterial ratio, Proteobacteria, Actinobacteria) and stable carbon decomposition genes.
• Specific genes in Rhizobiales and Pseudonocardiales orders were identified as key drivers promoting SOC priming.

Conclusions:

• Afforestation reshapes soil microbial community structure and function, enhancing stable carbon decomposition genes.
• These changes in microbial function under afforestation can promote soil organic carbon priming.
• Understanding these processes is vital for revegetation strategies in ecologically fragile areas.