The SPRUCE experiment is a large-scale study in northern Minnesota that examines how warming affects peatland ecosystems. Over five years (2012–2020), researchers applied different levels of warming—up to 9°C above normal—to intact bog plots and monitored changes in the peat soil profile down to more than 2 meters deep.

We measured how much carbon and nitrogen were stored in the peat, how dense the soil was, and the C:N ratio at the start of the experiment and after five years of warming. While the surface of the peat subsided slightly with increased temperatures, the total amount of carbon stored in the soil remained mostly stable. However, we found early signs of carbon redistribution, especially deeper in the peat, which may indicate the beginning of longer-term carbon loss. In some deep layers, nitrogen levels increased and C:N ratios declined, suggesting that warming may be changing how microbes break down organic matter. These below ground changes occurred even though surface layers appeared relatively stable. This study shows that deep peat may respond to warming sooner than expected. Long-term experiments like SPRUCE are essential for detecting early warning signs of carbon instability in peatlands and improving predictions of future carbon dynamics.