Enhanced below‐ground functioning is associated with higher plant resistance against drought: Implications for ecosystem functions

Abstract1. Recent evidence highlights the importance of low-abundant subordinate plantspecies in regulating ecosystem functions in grasslands experiencing droughtvia plant–microbe interactions. We hypothesized that subordinate and dominantspecies have distinct carbon (C) allocation and nitrogen (N) uptake patterns af-fecting soil microbes and their functions during a drought event.2. We collected soil cores with individuals of Paspalum dilatatum (dominant) orCynodon dactylon (subordinate) from two independent field drought experimentsin mesic Australian grasslands. Cores were subjected to a dual-pulse labelling with13 CO2 and 15NH415NO3 . Stable isotopes were traced in plant biomass and themicrobial community (PLFA-SIP, DNA/RNA-SIP and NanoSIM), and soil nutrientcycling was measured via enzymatic activities.3. The subordinate species invested more C below-ground and had higher N uptakein response to drought compared to the dominant, and the active soil microbialcommunity displayed small but consistent differences. The subordinate speciesshowed higher arbuscular mycorrhizae colonization rates but with similar C ex-change to the dominant species in response to drought.4. Synthesis. Our results suggest that the subordinate species achieves higher droughtresistance in biomass and soil functions via increased below-ground functioning.