Carbon gifts can be found under Christmas trees
December 26, 2012
In recent years, artificial Christmas trees have grown in popularity with people preferring them over real trees for various reasons. One common reason is the wide-spread belief that cutting down a real tree each year is harmful to the environment. Recent research, however, suggests that, if the soil stays healthy, just the opposite may be true. Buying a real Christmas tree could, in fact, help the earth.
The soils under the trees in tree farms offer many environmentally friendly advantages over soils used for other purposes, such as pastureland. Tree farmers generally don’t plow their fields. This means that soils are not disturbed and roots and dead needles build up reducing the amount of carbon dioxide released by the soils. Also, the tree farm soils contain a lot of carbon – about 10 times more than the amount of carbon in the trees themselves. These tree farms, then, are potential storage areas for carbon that could help alleviate greenhouse gas accumulation. If more carbon is sequestered in soils, there will be less of it in the atmosphere to contribute to global warming.
To better understand the benefits of tree farms, a research team from Villanova University, headed by Samantha Chapman and Adam Langley, looked at the carbon stored in the soils and the effects of groundcover, vegetation grown between the trees, on that storage. Their results were published in the Nov.-Dec. issue of Soil Science Society of America Journal. They found that tree farm soils retained two different types of carbon longer than pastures and that farms with more groundcover had more soil carbon content.
Soil carbon is often split into separate pools that indicate how readily the carbon might be broken down and therefore how long it might be stored. Active carbon breaks down easily and turns over in a matter of days while slow carbon pools and recalcitrant pools are more resistant to breakdown and remain in soils for centuries or even millennia.
The researchers found that the active and slow carbon pools in the tree farm soils stayed around longer than the same pools in pasture soils. If carbon storage is a major concern in an effort to reduce greenhouse gases, tree farms would be a more beneficial land use than pastures.
“All carbon is not the same,” says Chapman. “Christmas trees might produce carbon that is more difficult for bacteria and fungi to eat and therefore stays in the soil longer. Carbon like this could provide a long-term offset to climate change.”
Additionally, the level of recalcitrant carbon in the tree farm soils was different depending upon the amount of groundcover in between the trees. A tree farm with twice as much groundcover as another farm also had double the amount of recalcitrant carbon in its soils. By increasing the amount of groundcover on their farms, Christmas tree farmers could increase the carbon stored in their soils.
“We recommend lower herbicide usage to increase soil groundcover and reduce soil erosion, and many farmers are already using these techniques,” explains Chapman. “Other researchers have shown that native clover may be a good option for ground cover. It also brings nitrogen into the soil, reducing the need for fertilizers.”
While tree farms are not cultivated specifically for carbon storage, farmers could manage their land to maximize this beneficial side effect. Because the farmers would be releasing less carbon into the atmosphere than if their land was managed in the more traditional manner of eliminating groundcover, they could sell that offset to others wanting to make up for their carbon output.
For tree farms to continue to prosper, however, they must have customers. Chapman hopes that people will continue to see the beauty and benefit of buying a real Christmas tree.
“Christmas tree farming is a sustainable and low-intensity land use, and buying a real tree contributes to local economies,” says Chapman. “Trees are recyclable and are even used to make wildlife habitats in some communities. If a Christmas tree farmer is using the best practices, the farm itself could be a wildlife habitat and keep greenhouse gases out of the atmosphere.”
View the abstract online at: https://www.soils.org/publications/sssaj/abstracts/76/6/2221