Forest soils increasingly extract methane from atmosphere

Forest soils have an important role in protecting our climate: they remove large quantities of methane - a powerful greenhouse gas - from our atmosphere. Researchers from the University of Göttingen and the Baden-Württemberg Forest Research Institute (FVA) evaluated the world’s most comprehensive data set on methane uptake by forest soils. They discovered that under certain climate conditions, which may become more common in the future, their capacity to absorb methane actually increases. The data is based on regular measurements at 13 forest plots in south-western Germany over periods of up to 24 years. The study found forest soils absorb an average of three percent more methane per year. The researchers attribute this to the climate: declining rainfall leads to drier soils which methane penetrates more easily than moist soils. In addition, microorganisms break down methane more quickly as temperatures rise. The results were published in Agricultural and Forest Meteorology.

The researchers measured methane uptake by the soil. They measured soil gas profiles which reflect the chemical composition of the air in the soil at various depths. The data set comes from the FVA’s soil gas monitoring programme. Over a period of many years, samples of air from the soil were taken every two weeks using thin tubes inserted into the earth and analysed in the laboratory. The researchers verified their calculations with independent measurements which involved placing an airtight measuring chamber on the soil surface. If the concentration of a gas such as methane decreases inside the chamber, it is possible to calculate whether and how much gas is being absorbed by the soil.

The data revealed significant differences between the locations studied. Overall, however, it showed that forest soils in south-western Germany absorb large amounts of methane from the atmosphere - especially when annual rainfall decreases and temperatures rise. "Our long-term data shows that climate change does not necessarily have a negative impact on how much methane forest soils absorb. While the largest study to date from the US found a decline in methane uptake of up to 80 per cent due to increasing rainfall, our significantly more comprehensive field study in south-western Germany found the opposite, " explains Professor Martin Maier at Göttingen University’s Department of Crop Sciences, who led the study and was previously involved in the FVA’s soil gas monitoring programme. "We observed a significant long-term increase in methane uptake in the forest areas we studied." Dry soils contain more air-filled pores than wet soils. This makes it easier for methane to penetrate the soil. At the same time, microorganisms break down methane in the soil slightly faster when it gets warmer.

The results contradict current international meta-analyses. These studies, in which researchers summarise the results of many investigations, tend to conclude that methane uptake in forest soils is decreasing. According to the researchers, their recently published study highlights the importance of considering the data at different areas and regions over a long time period. "Our results make it clear that taking a series of measurements over many years and running monitoring programmes are indispensable for assessing the real effects of climate change," says Maier.

Original publication: Lang, V. et al. "Trend analysis of methane uptake in 13 forest soils based on up to 24 years of field measurements in south-west Germany". Agricultural and Forest Meteorology (2025). DOI:   10.1016/j.agrformet.2025.110823