Climatic Drivers of Soil Organic Matter Decomposition.

Soil organic carbon, the major component of organic matter, is a key indicator of soil quality, and a knowledge of the effects of climate change on soil carbon stocks will be of vital importance to the sustainability of future land use. Additionally, soil to a 1-meter depth contains about three times the amount of carbon as the atmosphere. Therefore, even small changes to the soil stocks can have major implications to the global carbon balance, and therefore climate change.

Loss of organic matter in soil is one of many processes that degrade soil. Therefore, it is vital to understand the processes that affect the rate of its decomposition. Over recent decades, it has become increasingly clear that temperature and precipitation patterns will change by the end of the century in many regions that are currently key to agriculture in response to increasing concentrations of CO₂ and other greenhouse gases. These factors each have an important influence on organic matter decomposition.

This session will summarize key findings and the current status of research on the effects of temperature, moisture, and elevated CO₂ concentrations on the decomposition of organic matter. There has been extensive research and debate over the past several decades, with little scientific consensus, but clarity is emerging as the debate refocuses on the role of temperature and moisture on the specific factors that control decomposition. Recent findings regarding elevated CO₂ concentrations are indicating eventual losses of soil carbon, not the gains previously theorized.

The combined stresses will have adverse effects on agriculture and are expected to decrease productivity and affect the capacity of soil to sequester and hold carbon, which in turn affect the sustainability of agriculture and humanity’s ability to feed itself. Possible solutions for resilience will also be presented.