Globally rising soil heterotrophic respiration over recent decades

It's important to note that this is a finding based on observations in the real world. This is not a tightly controlled lab experiment. Soils around the globe are responding to a warming climate, which in turn can convert more carbon into carbon dioxide which enters the atmosphere. Depending on how other components of the carbon cycle might respond due to climate warming, these soil changes can potentially contribute to even higher temperatures due to a feedback loop.

Ben Bond-Lamberty, first author of the study, Joint Global Change Research Institute

• States that global soils store at least twice as much carbon as Earth’s atmosphere
• States that the global soil-to-atmosphere (or total soil respiration, RS) carbon dioxide (CO2) flux is increasing, but the degree to which climate change will stimulate carbon losses from soils as a result of heterotrophic respiration (RH) remains highly uncertain
• Finds that the rate of increase of CO2 loss is outpacing that of CO2 uptake by plants; this is likely due to the imbalance in these rates of increase to enhanced activity of microbes that obtain nutrition by decomposing or mineralizing organic matter in soil
• Uses an updated global soil respiration database to show that the observed soil surface RH:RS ratio increased significantly, from 0.54 to 0.63, between 1990 and 2014 (P = 0.009)
• In other words, the rate at which microbes are transferring carbon from soil to the atmosphere has increased 1.2 percent over a 25-year time period, from 1990 through 2014
• The findings provide observational evidence that global RH is rising, probably in response to environmental changes, consistent with meta-analyses and long-term experiments
• The findings suggest that climate-driven losses of soil carbon are currently occurring across many ecosystems, with a detectable and sustained trend emerging at the global scale