Divergent thermal acclimation of plant and microbial respiration

Ecosystem respiration (Reco) has recently been shown to exhibit a unimodal response to temperature, with a temperature optimum (Topt). However, the Topt of the various biological components of Reco and how they acclimate to warming remain poorly understood. In this study, we investigated the presence of Topt and the acclimations of various biological components of Reco to warming, including plant respiration (Rplant) and microbial respiration (Rmicro), by conducting an eight-year warming experiment (+1.5°C and +2.5°C) in a Tibetan alpine meadow. Of the 720 respiration-temperature response curves examined, over 80% exhibited a clear Topt, with no significant difference observed between the Topt of Rplant and Rmicro. Notably, the Topt of Rplant and Rmicro increased significantly with soil temperature, reflecting thermal acclimation. However, the magnitude and underlying drivers of this acclimation differed substantially between Rplant and Rmicro. Under +1.5 °C warming, Rplant exhibited stronger acclimation than Rmicro. Rplant acclimation was positively associated with grass dominance, temperature, and soil total nitrogen, whereas Rmicro acclimation was more closely linked to temperature, microbial community composition, and respiration rates. In contrast, above- and belowground plant respiration showed consistent acclimation patterns. These findings provide empirical evidence that, although the Topt for plants and microbes is similar, their thermal acclimation differs. This suggests that plant and microbial adopt distinct thermal strategies to copy with future climate warming.