This study investigates the impact of long-term soil warming (+6°C) on the active populations of bacteria and archaea in a Subarctic grassland, using quantitative stable isotope probing (qSIP) to measure taxon-specific growth rates. The results show that while soil carbon and nitrogen pools decreased with warming, relative community growth rates increased. However, this increase was driven by a greater number of active bacterial taxa rather than faster-growing populations. Root presence enhanced bacterial growth at ambient temperatures but not at elevated temperatures, indicating a shift in plant-microbe interactions. The study reveals that the microbial warming response is more complex than previously thought, involving shifts in the number and diversity of active taxa rather than just faster-growing populations. Additionally, the indirect warming effects mediated by roots, such as changes in root-associated taxa, play a significant role in shaping microbial activities. These findings provide new insights into the mechanisms underlying the microbial warming response and highlight the importance of studying individual microbial populations to better understand the dynamics of the soil microbiome in a warmer climate.This study investigates the impact of long-term soil warming (+6°C) on the active populations of bacteria and archaea in a Subarctic grassland, using quantitative stable isotope probing (qSIP) to measure taxon-specific growth rates. The results show that while soil carbon and nitrogen pools decreased with warming, relative community growth rates increased. However, this increase was driven by a greater number of active bacterial taxa rather than faster-growing populations. Root presence enhanced bacterial growth at ambient temperatures but not at elevated temperatures, indicating a shift in plant-microbe interactions. The study reveals that the microbial warming response is more complex than previously thought, involving shifts in the number and diversity of active taxa rather than just faster-growing populations. Additionally, the indirect warming effects mediated by roots, such as changes in root-associated taxa, play a significant role in shaping microbial activities. These findings provide new insights into the mechanisms underlying the microbial warming response and highlight the importance of studying individual microbial populations to better understand the dynamics of the soil microbiome in a warmer climate.