Tree bark's seasonal swelling can fool growth measuring instruments
Gričar J, Eler K
Phenology
If you've ever strapped a growth band around a favorite tree to track its progress, this explains why those numbers can mislead you about how much new wood is really forming underneath.
Researchers cut tiny core samples from three tree species throughout a growing season to see what's really happening under the bark. They found that the bark itself puffs up and deflates as the season progresses, separate from the wood growth happening inside, which matters because instruments that measure trunk width can't tell the difference between bark swelling and actual wood growth unless you account for it.
Key Findings
Xylem (wood) growth accounted for very different shares of total stem increment across species: 40.5% in European black pine, 9.6% in manna ash, and 17.6% in European hop-hornbeam
Non-conducting phloem was the largest component of inner bark and the main driver of seasonal bark width changes
Inner bark width was similar at the start and end of the growing season, so subtracting it from total stem growth gives a reasonable year-end estimate of wood growth, even though its pattern differs from wood growth timing during the season
chevron_right Technical Summary
Scientists studying tree trunks found that the bark layer swells and shrinks with the seasons, which can trick standard growth sensors into overestimating how much wood a tree actually adds each year.
Abstract Preview
Original paper
The impact of seasonal variations in inner bark width and xylem growth on irreversible annual stem diameter measurements.
To better interpret continuous xylem growth measurements from dendrometers, we evaluated how the widths of developing xylem and phloem, along with seasonal trends in inner bark width (conducting ph...
open_in_new Read full abstractAbstract copyright held by the original publisher.
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