Hotter summers, colder winters, floods, drought — the rising volatility of weather often associated with climate change may be having on impact on a key soil health indicator. Soil organic carbon levels in soil could be impacted by changing climate.

In new work from Australia, researchers used digital techniques to predict how soil organic carbon may be altered by climate change. In a release about the study, lead researcher Jonathan Gray, comments: "Soil organic carbon is a major determinant of soil health. It influences many chemical, physical and biological properties of the soil, such as fertility and water-holding capacity." Gray is a senior scientist at the New South Wales Office of Environment & Heritage in Australia, and is also undertaking doctoral studies at the University of Sydney.

Gray and fellow researchers used 12 climate change models to predict how soil organic carbon levels vary with climate change. The models used in the study reflected a full range of projected global climate outcomes. They were also applicable to the specific study region of New South Wales in southeast Australia. However, the information does show climate change can impact soil carbon and has relevance worldwide.

Grey got varied results, noting that a majority of models showed a decline in soil organic carbon with climate change. However, a few actually predicted an increase. He attributes that variance to uncertainties within the climate change models. "We need more consistency between climate change projections before we can confidently predict how soil organic carbon levels will behave," he says.

The researchers did measure the level of impact and how soil carbon changes across different soil types. For example, they projected an average decline of soil organic carbon at less than 1 ton per hectare, or less than a half-ton per acre in sandy, low-fertility soils in dry conditions under cropping systems. The loss was 15 times higher for clay-rich, fertile soils in wet conditions under native vegetative regimes.

Predicting soil organic carbon changes is important, Gray says: "It would allow us to better prepare for and adapt to altered soil conditions. That would ultimately improve how we manage both agricultural and native ecosystems."

Higher resolution, better data
Gray and his colleagues combined different digital methods to achieve very high-resolution mapping. Instead of the typical 10-km resolution, the team achieved resolution of 100 meters. This allowed the researchers to link soil organic carbon changes with specific soil types or land use patterns.

“Our model offered a more conceptually simple, but still robust, alternative to the more complex dynamic modeling approaches that are usually used,” explains Gray.

While this study focused on New South Wales, Gray thinks the findings will apply to areas beyond the study site as well. “The actual map of expected soil organic carbon change is of most relevance to New South Wales,” he says. “But the key findings of the study are globally applicable.”

Gray is now trying to predict how other key soil properties, such as nutrients and acidity, will be affected by projected climate change.

Understanding how climate change affects soil properties may actually yield more accurate climate change models as well. “Being able to predict the potential of soils to store carbon or release it into the atmosphere will be crucial for future climate change modeling and mitigation strategies,” Gray says.

Read more of Gray's work in the Soil Science Society of America Journal.

Source: Soil Science Society of America