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Dear Michigan Climate News,

Can you find out if pine trees help as much as leafy trees with carbon dioxide? It would guide me on what trees I should be planting.

Sincerely,

Aspiring Arborist

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Dear Aspiring Arborist,

In short, both pine trees, a type of coniferous tree, and “leafy” trees, called deciduous trees, are beneficial in carbon sequestration, the process of capturing and storing carbon dioxide.To learn more, we asked a researcher who describes carbon as his favorite element, Christopher Gough. He is a biology professor at Virginia Commonwealth University and has done years of field research on Michigan forests.

“It’s more complicated than yes or no,” he said.

Pine trees, or conifers, he explained, are good at growing in environments that have been recently disturbed or damaged, like by wildfire or pests. In the early stages of their life they grow quickly, soaking up carbon dioxide along the way through their needles. Pine needles are leaves too, just like the leaves of their deciduous counterparts.

“Pines typically do a really good job in young forests accumulating carbon rapidly,” he said, at a rate much faster than deciduous trees.

In Michigan, coniferous trees, like the red pine and jack pine tend to live shorter lives than deciduous trees.

Deciduous trees like maple and hickory tend to live longer and take “more of a slow and steady model” to carbon sequestration, Gough said.

When you consider that conifers absorb more carbon in the beginning, while deciduous trees absorb carbon at a slower rate, but live longer, the two trees’ ability to sequester carbon is “basically equivalent” Gough said.

At the University of Michigan Biological Station in Pellston, Gough is studying what makes trees able to sequester carbon better, and more reliably. One way he studies this is by measuring how much trees have grown in the forests and converting that into carbon sequestration. He also uses a 150-foot tall tower, called a meteorological flux tower, to constantly measure how much carbon dioxide is entering and leaving the forest.

For more than 20 years this tower has been collecting data, earning the title of one of the longest-running records of carbon sequestration of a forest, in the entire world.

The most surprising finding during Gough’s research came from an experiment during which he simulated a major disturbance to the forest, killing 40 percent of the leaves on the trees in the study area. The simulated disturbance was similar to that of a pest, like the emerald ash borer, which destroyed millions of trees across the country in the early 2000s. Recordings were then taken of how much carbon dioxide the disturbed trees were able to capture, compared to nearby ones that were undisturbed.

Despite a significant reduction in the number of leaves on the trees, there was no change in carbon sequestration rates for the trees that were disturbed.

“Forest ecosystems are very resilient,” Gough said.

The more biodiverse a forest is, the better it is at sequestering carbon. Increasing temperature extremes caused by climate change put a lot of stress on forests, but biodiversity helps the forest to be more resilient and stable. In fact, there is some research that biodiverse forests can store two times as much carbon as forests with just one tree species.

“Forests that are more structurally complex, tall trees, short trees, trees that are in between, those forests tend to be better equipped at sequestering carbon in a more stable manner as climate extremes enter the picture,” he said.

So, it isn’t as important what kind of tree you plant, it’s the overall health and functionality of the ecosystem that’s important to consider.