High‑Resolution Scans Show Dead Branches Move With Humidity Changes

Scientists at Heidelberg University have shown that dead tree branches are not stationary; they gently oscillate in response to shifts in surrounding humidity, a behavior recorded using high‑resolution laser scanning.

The researchers used terrestrial LiDAR to capture three‑dimensional point clouds of selected limbs over several days. By aligning these scans with continuous humidity readings, they mapped tiny expansions and contractions that matched the fluctuations in atmospheric moisture.

Wood behaves hygroscopically, so even after a tree dies its cellular matrix continues to take up water from the air and release it as conditions vary. This uptake swells the fibers, while drying causes them to shrink. The team found that these dimensional tweaks, invisible to the eye, produce measurable movements on the order of millimetres.

Recognizing this concealed dynamism carries practical weight. Forest engineers and ecologists depend on precise models of branch stiffness and load‑bearing capacity to forecast tree reactions to wind, snow, or other stresses. If dead wood subtly reshapes itself throughout the day, existing models might require adjustment, particularly in locales with sharp humidity swings.

The investigation was carried out together with the Finnish Geospatial Research Institute (FGI), merging expertise in geoinformatics and remote sensing. This cross‑institutional collaboration let the team test their approach under varied climatic conditions, bolstering confidence in the results.

Future work will broaden monitoring to larger portions of forest canopies and feed humidity‑driven motion data into comprehensive ecological simulations. Such integration could sharpen predictions of forest stability in climate‑change scenarios, where shifting humidity patterns may influence the mechanical behavior of both living and dead vegetation.