Extreme high temperature erodes the greenhouse gas mitigation edge of plant intercropping

Plant-microbe interactions regulate soil greenhouse gas (GHGs) fluxes, yet their responses to climate extremes remains unclear. In a factorial experiment combining plant composition (bare soil, monoculture, intercropping) with contrasting temperatures, we found that the soil global warming potential (GWP) mitigation effect of intercropping under extreme high temperature (EHT) significantly declined by 17.4 % compared with normal temperature (LT). EHT suppressed plant biomass (-41.9 % to -86.6 %), diminished soil carbon sequestration (-0.9 % to -6.9 %), and increased the r/K strategy ratios (+0.7 % to +5.7 %). It further erased the clear separation between intercropping and monoculture microbial communities evident under LT and upregulated key N-loss genes (e.g., nirS, norC), jointly undermining the microbial basis of plant-mediated GHGs mitigation. Our findings highlight that while plant diversity stabilizes soil biogeochemistry and constrains GHGs release, its buffering efficacy is inherently fragile under EHT, providing new evidence of limits to biotic regulation in a warming world.