Microbial feedback drives soil carbon fixation and nutrient transformation during Euphorbia jolkinii expansion in...

Euphorbia jolkinii (E. jolkinii), a native toxic weed widely occurring in the subalpine meadows of the Southern Tibetan Plateau, has increasingly expanded in recent years, leading to reduced forage availability and potential livestock poisoning. Although its ecological impacts are evident, the mechanisms supporting its spread remain inadequately clarified. In particular, how expansion intensity interacts with soil microorganisms and carbon transformation processes requires further exploration.

Field patches exhibiting different levels of E. jolkinii expansion were selected as the research subjects. Across different expansion levels, variations in soil carbon fractions, microbial community composition and diversity, as well as functional genes involved in the carbon cycle, were systematically analyzed.

The expansion of E. jolkinii was associated with a significant decrease in soil pH along with concurrent increases in the contents of available nitrogen (AN), available phosphorus (AP), total nitrogen (TN), total phosphorus (TP), and available potassium (AK). Expanded patches exhibited a distinct microecological environment characterized by the enrichment of key microbial taxa, particularly Bradyrhizobium and Bacillus. These microbial groups were coupled with shifts in soil carbon fixation and organic carbon turnover potential, corresponding to significantly higher contents of soil organic carbon (SOC), easily oxidizable organic carbon (EOC), microbial biomass carbon (MBC), and dissolved organic carbon (DOC).

Euphorbia jolkinii expansion is closely associated with the enrichment of soil microbial guilds involved in carbon cycling. The concurrent enhancement in soil carbon fixation and transformation potential corresponds to altered nutrient availability, suggesting a potential microbial feedback mechanism that aligns with the successful encroachment of this species in subalpine meadows.