Trees in forests produce methane, a greenhouse gas that contributes to climate change. This is a newly discovered phenomenon, and scientists don't yet understand where and when trees release this methane.

We studied over 150 trees across 16 species in Connecticut forests and found methane-producing microbes throughout the wood, especially in heartwood. Nearly all trees contained these microbes, with concentrations varying widely among trees. Sugar maples had the most while evergreens had fewer.

We discovered that methane emissions don't follow predictable patterns. Instead, we found 'hotspots' of methane production scattered throughout individual trees. When we cut down one oak tree and measured emissions from bottom to top, the highest emissions came from the middle of the trunk, not the base.

These microbes create methane in oxygen-free pockets within the wood through natural fermentation processes, similar to how bacteria make methane in wetlands. However, the patchy distribution of these microbial communities makes it difficult to predict how much methane entire forests produce.

Our findings suggest that current methods for estimating forest methane emissions may be seriously underestimating the true amounts because they only measure near the ground and assume uniform patterns that don't actually exist.