February 27th, 2012 by

The forest floor (Credit: Jan Vanaverbeke)

There’s a lot we still don’t know about climate change, but one thing we do know is that forests are a vital piece of the puzzle. Forests are so intertwined with carbon, and carbon with climate, that there is no denying the role forests play in slowing climate change and addressing its effects. Despite the complexities of that relationship, in my mind, it always comes back to the simple fact that trees absorb CO2 and store carbon. Now, a researcher is suggesting that one of the most important pieces of the puzzle is found in a forest, but it isn’t the trees: It’s the soil.

Justin Whisenant, a senior student researcher at Texas A&M University, says that while so many focus on the role of carbon in the air and the trees, its role in the soil is often overlooked. Yet, much of the carbon cycle does not take place over our heads, but under our feet. In fact, his research states that a forest ecosystem stores twice as much carbon in the soil as is it does in “aboveground biomass,” meaning trees and other plants.

If you think about it, a forest floor is covered with carbon-based matter, from tree roots to dead leaves and fallen tree limbs. It decomposes, and the carbon remains in the soil. Then, microbes in the soil continue to decompose the matter, and in the process, they release the stored carbon back into the atmosphere — a process known as microbial respiration. Whisenant’s research explores ways to influence that process and perhaps expand a forest’s ability to store carbon.

His research involved two months of testing soil samples from different stands of a loblolly pine forest in Florida. Each testing area was treated with differing levels of nitrogen and phosphorous, both common ingredients in fertilizers. Whisenant’s tests showed that both substances, particularly nitrogen, slow the rate of microbial respiration, which leaves more carbon stored in the soil.

Nitrogen, testing, microbes: What does it all mean? The findings suggest that certain common methods of forest management — such as using fertilizer — could help increase a forest’s carbon-storage capacity. And since many forests that border urban areas already receive larger levels of nitrogen due to various emissions, they may already be storing increased levels of carbon — a natural reaction that could prove important as CO2 levels in the atmosphere continue to grow.