Structurally Complex Forests Better At Carbon Capture, Study Shows

You may already know that diverse forests are better at sequestering carbon than monoculture forests. However, new research suggests that the equation may not come down just to forest species diversity – but is largely influenced by the forest structure. This was discovered by a study called “High Rates of Primary Production in Structurally Complex Forests,” led by researchers at Virginia Commonwealth University and published in the latest issue of “Ecology,” a journal of the Ecological Society of America.

What Is Forest Carbon Sequestration?

To truly understand the implications of the new findings, we need to define the two main concepts that the study revolves around.

Structurally complex forest is the type of woodland where the arrangement of vegetation is highly varied – the ecosystem includes trees of different sizes, height, and age. The opposing example is the cultivated forest, which is usually a monoculture grown primarily for timber. Trees in these forests are often members of the same species, similar in age and size, and spaced out evenly.

Carbon sequestration is the process in which plants take carbon from the air in the form of carbon dioxide during photosynthesis. The trees turn the CO2 into their tissue – the wood – in the form of more complex carbon molecules, and also they store some of it in the ground. That way, the carbon is “fixed” within the wood until it enters the process of decay (or until it’s burned). Carbon sequestration is the main way in which the trees can help us mitigate the climate crisis and offset the excess carbon we produce both directly through the burning of fossil fuels, and indirectly by increasing natural events such as forest fires.

The study is the first to demonstrate that the forest’s structural complexity is superior in predicting carbon sequestration potential when compared to tree species diversity. Chris Gough, Ph.D., an associate professor in the Department of Biology and a corresponding author of the study says that “study shows that more complex forests are better at taking up and sequestering carbon in wood and, in doing so, they leave less carbon dioxide in the air.”

And why do structurally complex forests outcompete the simple ones?

Gough suggests that many layers of leaves may promote the more efficient use of light, a primary factor in photosynthesis and carbon sequestration. “In other words, forests that are structurally variable and contain multiple layers of leaves outperform structurally simple forests with a single concentrated band of vegetation,” he said.

The Study’s Use Of LIDAR Technology

The study is also notable for its use of modern technology to upgrade our fundamental environmental knowledge. The researchers used a combination of their own field data, and the data from the National Ecological Observatory Network (NEON) which generates long-term, publicly available data for different ecosystems in the U.S. for understanding long-term ecological processes. It builds on previous research supported by the National Science Foundation that demonstrated how laser-based technology called LiDAR can map the distribution of leaves within a forest canopy at very high resolution.

The VCU study now suggests that LiDAR can be utilized to make predictions about a forest’s carbon sequestering potential and deliver superior results in comparison to conventional approaches such as recording biodiversity and leaf quantity. According to Gough,  “These results, we hope, push the science forward by showing that how a forest is put together matters for carbon sequestration, and this relationship extends broadly to a number of different forests, from evergreen to deciduous and mid-Atlantic to Midwest.”

The corresponding author hopes that the estimation of structural complexity from satellites will greatly improve the possibility of precisely estimating and predicting global carbon sequestration in forests – one of the crucial factors in climate crisis mitigation.

The Study

Gough, C. M., Atkins, J. W., Fahey, R. T., and Hardiman, B. S.. 2019. High rates of primary production in structurally complex forests. Ecology100( 10):e02864. 10.1002/ecy.2864 

McNeal, B. Structurally complex forests better at carbon sequestration. Phys.org. https://phys.org/news/2019-08-complex-forests-carbon-sequestration.html

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