Plant community micronutrients mediate the soil carbon stock by altering plant growth, reproduction and survival trade-offs

Despite the essential role of micronutrients in plant metabolic processes and carbon cycle, the mechanisms by which micronutrients regulate plant community traits remain poorly understood. Here, we used a long-term experiment to explore the potential mechanisms of plant community micronutrients and traits along a precipitation gradient. Our results showed that plants shifted toward lateral growth and asexual reproduction over time. From 1985 to 2022, the plant community Fe content increased by 18.8% in the north but declined by 25.2% in the south of the typical steppe. Furthermore, plant community growth and reproduction were sensitive to both micronutrient contents and uptake efficiencies in the north of the typical steppe. While plant community Mn and Zn contents enhanced growth longitudinally, Zn and Fe uptake efficiencies hindered sexual reproduction. Furthermore, soil moisture and GDP per capita were the key drivers of micronutrient variation in the north and south of the typical steppe, respectively. Precipitation fluctuations primarily regulated community traits across all sites. In the arid site, micronutrient-driven shifts in reproduction stabilized the soil carbon stock by balancing biomass allocation. These findings can help us to better understand the coupling of plant micronutrients, traits, and soil carbon stocks, thereby providing the basis for a scientific grassland conservation strategy under global change scenarios.