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| The data on methane uptake comes from soils in beech and spruce forests, like the typical Central European beech forest shown here. Photo Credit: Martin Maier |
Scientific Frontline: "At a Glance" Summary
- Main Discovery: Long-term monitoring reveals that forest soils in south-western Germany are increasingly extracting methane from the atmosphere, contradicting previous international meta-analyses that predicted a climate-driven decline in this function.
- Methodology: Researchers analyzed the world's most comprehensive dataset on methane uptake, utilizing soil gas profiles from 13 forest plots collected bi-weekly over a period of up to 24 years and validated via airtight surface chamber measurements.
- Key Data: The study observed an average annual increase in methane absorption of 3%, a stark contrast to a major US study that reported a decline of up to 80% under conditions of increasing rainfall.
- Significance: These findings challenge the assumption that climate change universally exerts a negative impact on soil methane sinks, demonstrating instead that drier and warmer conditions can enhance the capacity of forest soils to filter greenhouse gases.
- Future Application: The results highlight the indispensability of long-term, region-specific monitoring programs for accurately calibrating climate models and assessing the real-world effects of environmental shifts on soil processes.
- Branch of Science: Agricultural and Forest Meteorology, Soil Physics.
- Additional Detail: The increased uptake is mechanically attributed to drier soils possessing more air-filled pores for gas penetration, combined with higher temperatures that accelerate the microbial breakdown of methane.
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| Soil gas monitoring using automatic collectors: soil air samples were taken regularly over a period of several years using pipes permanently inserted into the soil. Photo Credit: Martin Maier |
Forest soils play 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 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 program. 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 analyzed 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 gas such as methane decreases inside the chamber, it is possible to calculate whether and how much gas is being absorbed by the soil.
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| Weather stations provided the climate data: during the study period, average temperatures rose at the forest sites, while annual rainfall declined in most cases. Both these trends are typical of the local climate change. Photo Credit: Martin Maier |
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 program. “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-analysis. These studies, in which researchers summarize 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 period. “Our results make it clear that taking a series of measurements over many years and running monitoring programs are indispensable for assessing the real effects of climate change,” says Maier.
Reference material: What Is: Greenhouse Gas
Published in journal: Agricultural and Forest Meteorology
Authors: Verena Lang, Valentin Gartiser, Peter Hartmann, and Martin Maier
Source/Credit: University of Göttingen
Reference Number: ags012826_01