Minnesota forest experiment shows trees limit respiration rise despite 3.4°C warming

A long-term field experiment in northern Minnesota, part of the Boreal Forest Warming at an Ecotone in Danger (B4WarmED) project, heated soil and canopy temperatures by about 3.4 °C for multiple growing seasons. Seedlings of ten boreal and temperate tree species were monitored, focusing on leaf respiration—the process that releases CO₂. Contrary to common climate-model assumptions, the warmed trees showed only a 5 % rise in respiration rates, whereas without acclimation the increase would have been roughly 23 %.

The researchers attribute the muted response to strong physiological acclimation, stronger than that observed in short-term lab studies. They caution that warming still affects forests, but the finding suggests that forests may offset more carbon than many models predict if similar acclimation occurs broadly. The study highlights the need to incorporate such adaptive responses into future climate projections.