Scientists conducting the world’s longest-running soil warming experiment have documented evidence that contradicts previous assumptions about carbon storage in forest soils. Researchers at the Marine Biological Laboratory, led by Distinguished Scientist Jerry Melillo, maintained heated plots in the Harvard Forest in central Massachusetts at temperatures 5°C above ambient conditions throughout the study period. The 5-degree increase was selected to represent the upper range of global warming projections existing at the experiment’s outset.
Over nearly four decades of observation, the research team monitored how soil ecosystems responded to sustained warming. The investigation revealed that microbial communities in soils play critical roles in decomposing organic matter and recycling nutrients necessary for plant growth. As temperatures increase, these microbial populations shift in composition and activity, accelerating the breakdown of carbon stored in soil. Notably, during the fourth decade of the experiment, researchers observed that even stable portions of soil organic matter—previously thought to resist temperature-driven decomposition—began breaking down at measurable rates.
The decomposition of these long-term carbon stores releases carbon dioxide into the atmosphere, suggesting that forest soils may contribute greater quantities of CO2 to the atmosphere under future warming scenarios than previously projected. This finding indicates a potentially stronger climate feedback mechanism, where planetary warming triggers increased soil carbon release, which in turn adds more greenhouse gas to the atmosphere and may fuel additional warming.
Scientists indicate that incorporating these newly identified processes into climate models should enhance the accuracy of future projections. The research provides improved understanding of how Earth’s carbon cycle responds to temperature increases. Melillo notes that future warming trajectories depend substantially on actions to reduce greenhouse gas emissions and mitigate deforestation. Global average temperatures have risen approximately 1.1 to 1.4°C since the Industrial Revolution, with further increases contingent on emission reduction efforts.
Originally reported by ScienceDaily. Read the full story →