November 30, 2015
The International Year of Soils: Soils and Climate
Several components of the earth influence its climate. The climate system involves the earth's oceans, land surfaces, soils and the atmosphere, according to Kendra McLauchlan, associate professor of geography at Kansas State University. The interactions among these components with one another and with various life forms on earth also play a role in climate.
Carbon is the fourth most abundant element in the universe, and the carbon cycle on earth is one of the most important interactions that influences climate, McLauchlan said. Carbon on earth is found in various forms: in oceans as carbonic acid, in the atmosphere as carbon dioxide, in wood as cellulose and in the soil in the form of organic matter.
"Soil contains a large portion of the carbon on earth," McLauchlan said. "It contains more carbon than all the carbon dioxide in the atmosphere and all the forests on earth combined."
Carbon in the soil is mostly stable and remains locked away beneath the surface, she added. However, it can be oxidized back into the atmosphere by exposure to oxygen or when eaten by microbes and turned into carbon dioxide.
"The greenhouse gas carbon dioxide is this little molecule that has the amazing ability through its molecular structure to retain solar radiation and emit it back to the atmosphere," McLauchlan said.
Therefore, the carbon cycle helps keep the planet warm and supports life, but too much carbon dioxide in the atmosphere can have the negative effect of warming the planet too much.
Because soil is a main player in the global carbon cycle, "Soils and Climate" is a fitting November theme for the 2015 International Year of Soils, which involves a coordinated effort to educate the public about the importance of soil.
Retaining carbon in the soil
"It's a great idea to keep as much carbon in the soil as possible," McLauchlan said. "Conservation tillage management and other activities land managers can do help keep carbon in the soil. Most of those activities involve using plant matter to retain carbon inputs and avoiding loss pathways, such as erosion or disruptive tillage practices that may oxidize the carbon."
Examples of ways to retain carbon in the soil could include planting riparian buffers and cover crops.
"Anytime we can get plants growing in the soil and adding their carbon from the atmosphere to the soil will increase soil organic matter stocks," McLauchlan said.
Further, she said land managers can use conservation tillage practices, such as no-till farming, to keep soil and carbon storage more stable. Many examples from past civilizations show how intensive agricultural tillage practices that gradually removed a bit of soil every year eventually led to their demise.
"The message from those past civilizations is to watch for these slow changes and be as careful as you can with the soil resource," McLauchlan said. "The processes that form soil are slow, so just a little bit of loss every year can erode your soil resource."
Reflectance and water storage
In addition to carbon storage, soil can influence climate in two other key ways—reflectance of solar radiation and water storage, the paleoecologist said.
The soil surface reflects solar radiation, and whether the soil is dark or light can either serve to cool or heat the atmosphere. Water is held in soil and can either be retained in liquid form or released as water vapor. When the latter occurs and water vapor is released into the atmosphere, it serves as a greenhouse gas that can warm the planet, similar to the mode of carbon dioxide.
To watch a video interview about "Soils and Climate" that features McLauchlan, log on to the K-State Research and Extension YouTube page. The Soil Science Society of America has numerous resources for the public, teachers and children about soil and each monthly theme for the International Year of Soils. Log on to www.soils.org.