A research team led by Prof. Li Dejun from the Institute of Subtropical Agriculture, Chinese Academy of Sciences, provides the first evidence in a subtropical karst forest that tree species diversity can significantly suppress priming effects, and elucidates a novel synergistic regulatory mechanism centered on alleviating microbial energy limitation-functional guild transition-gene expression rewiring.

These findings offer critical theoretical support for the synergy between biodiversity enhancement and forest C sequestration.

Their latest research was published in Ecology Letters on May 17.

Soil organic carbon (SOC) stability is central to the sustainability of terrestrial ecosystem carbon sinks. The priming effect triggered by fresh carbon (C) inputs can accelerate the decomposition of native SOC, representing a key process governing SOC retention or loss. Nature-based climate solutions largely emphasize enhancing plant diversity to increase C inputs. However, whether diversity exacerbates priming effect and causes C loss, or suppresses the priming effect and strengthens carbon stability, has remained a major unknown in global C cycle models. Particularly in subtropical forest ecosystems, systematic mechanistic understanding is lacking regarding how tree species diversity regulates microbial metabolism, functional genes, and community networks, thereby altering the magnitude of soil priming effects.

Based on a tree species diversity gradient established across 45 forest plots in the Guangxi Mulun National Nature Reserve, the researchers systematically dissected the driving patterns and regulatory pathways of the priming effect using a technical framework including ¹³C isotope labeling incubation, metagenomic sequencing, microbial network analysis, and structural equation modeling (SEM).

The results showed that soil priming effects decreased significantly and linearly with increasing tree species diversity, shifting from strong positive priming to weak or even negative priming. This relationship remained robust after strictly controlling for environmental factors, stand structure, and mycorrhizal types, confirming tree species diversity as an independent core factor suppressing the priming effect.

Furethermore, they advances the theoretical framework of biodiversity-regulated soil carbon stability from the perspective of the priming effect, clarifying that increasing tree species diversity can lock in native soil carbon and reduce carbon loss while boosting C inputs.

“Our findings highlight that forest carbon sink assessments and Earth system models must incorporate tree species diversity and microbial functional strategy parameters,” Dr.Duan Pengpeng, the first author emphasised, “It provides key scientific support for ecological restoration, close-to-natural transformation of plantations, and carbon neutrality pathway optimization in subtropical and karst regions of China.”

Contacted: Li Dejun

E-mail: dejunli@isa.ac.cn

A conceptual framework illustrating how tree species diversity suppresses the soil priming effect(Imaged by HOU Xinyu)