麻豆淫院

The global demand for wood-based products is constantly increasing, creating a challenge for the logging industry. In an attempt to keep up in a sustainable manner, the industry replaces logged areas with tree farms and nurseries to eventually replenish supplies. This use and regrowth of wood has also been thought to help maintain a carbon sink. While this may be true to some extent, a new study has found that an important source of carbon loss is often being left out of the equation.

The research, in the Proceedings of the National Academy of Sciences, details a three-year-long study on dissolved organic materials (DOM) found in runoff near logging areas in Ontario, Canada. Researchers involved in the study conducted monthly sampling of stream and soil water to assess the DOM concentration and molecular composition in four catchments, two that had been logged and two controls with similar climate, geology, and topography. They used ultrahigh-resolution mass spectrometry and optical spectroscopy to determine the molecular composition of the DOM.

The study found that DOM concentrations quadrupled during the first two months after tree harvest and subsided afterward. This initial increase is likely due to soil disturbance and loss of tree cover. The team found that the composition of DOM became more reactive and diverse, with more compounds available for microbial use, and that these molecular changes persisted for at least 2 years after harvest.

The authors explain why this matters: "Once released as DOM into headwaters by logging, terrestrial carbon may be more likely to be respired back to the atmosphere than in unimpacted streams or had it remained as mineral associated organic matter in soils."

They note that not all carbon in DOM necessarily makes its way back into the atmosphere, but microbes are likely to increase the release of carbon from certain DOM compositions through respiration.

"The likelihood of terrestrial carbon returning to the atmosphere ultimately depends on the composition of DOM entering headwaters. Forest harvesting activities can change DOM composition by increasing overland and near surface lateral flow, physically disturbing soils with heavy machinery, and generating woody debris. Compared with soils, especially mineral-associated organic matter, DOM is also far more reactive because it is readily available for microbial metabolism."

Overall, the study indicates that these changes could reduce the net carbon storage benefits of wood products, and the researchers estimated that 6.4% of the carbon removed as timber was lost as DOM to streams. This might not sound like much, but in some cases, it is enough to shift logging from a carbon sink to carbon-neutral or even a carbon source.

Ultimately, the results indicate that carbon loss from DOM runoff should be considered and calculated when estimations of the carbon sequestration of logging activity are being made. Then, policymakers and strategists can use these findings to revise carbon accounting and climate mitigation strategies.

"Our results demonstrate that without consideration and inclusion of aquatic carbon fluxes as part of BMPs, the potential carbon sequestration from wood harvest, particularly in northern regions like those examined here, will be miscalculated," the study authors write.

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