Thursday, December 6, 2012

Canopy structure more important to climate than leaf nitrogen levels

Terra Daily via SPX: Claims that forest leaves rich in nitrogen may aid in reflecting infrared radiation - helping cool the atmosphere - have been challenged by new research that shows that the structure of tree canopies is a more important factor in infrared reflection. Recent studies have noticed a strong positive correlation between the concentration of nitrogen in forests and infrared reflectance measured from aircraft and satellites.

Some scientists have suggested this demonstrates a previously overlooked role for nitrogen in regulating the earth's climate system.

However, a new paper in Proceedings of the National Academy of Sciences, shows that the apparent relationship between leaves' nitrogen levels and infrared reflection is spurious and it is in fact the structure of forest canopies (the spatial arrangement of the leaves) that determines their ability to reflect infrared light.

The authors, including Professor Philip Lewis and Dr Mathias Disney (UCL Geography), show that the richer in nitrogen individual leaves are the worse at reflecting infrared radiation they become.

However, the complex arrangements of trees with radically different arrangements of leaves within a forest can act to mask this effect, making it appear as if higher levels of leaf nitrogen are leading to increased infrared reflection....

A tree canopy in Sri Lanka's Sinharaja Forest Reserve, shot by Chamal N, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

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