Fig. 2.

Conceptual diagram of instantaneous delta respiration (∆R) and temperature (∆T) response between warmed (red symbols) and control (blue symbols) treatments on a given day of measurements at the lower end of the temperature range (<25 °C). Circles represent sampling date in spring, whereas stars represent sampling date in summer. (A) All nondesert biomes, except boreal forests. Despite the increase of respiration with warming on a given day of measurements, the temperature response function (the dashed line) across the different colors (the warming effect) is similar to that across the different symbols (the seasonal temperature variation). (B) Boreal forests. Warmed plots (dashed line) had lower sensitivity compared with control plots (solid line). However, no significant differences in the y intercept were observed. (C) Desert. Warmed plots (dashed line) had a lower y intercept but higher sensitivity compared with control plots (solid line). (D) Temperate forest. Despite displaying similar temperature sensitivities, y intercepts of warmed plots (dashed line) were marginally (P = 0.06) lower than control plots (solid line). Delta response was always calculated as warmed value minus control value.