High‑Resolution Laser Scans Show Dead Branches Move With Humidity Changes

A team from Heidelberg University has shown that dead tree branches do in fact move, gently rocking in response to shifts in atmospheric humidity, a behavior recorded using high‑resolution laser scanning.

Using terrestrial LiDAR, the researchers captured three‑dimensional point clouds of chosen branches across multiple days. Aligning these scans with nonstop humidity readings let them chart tiny expansions and contractions that matched the fluctuations in moisture levels.

Because wood is hygroscopic, its cellular makeup keeps taking up water from the air and letting it go even after the tree is dead. This uptake makes the fibers expand, and drying makes them contract. The scientists found that these size changes, imperceptible without aid, translate into measurable shifts of a few millimetres.

Recognizing this concealed motion carries real‑world relevance. Engineers and ecologists who model branch rigidity and load‑bearing need precise data to forecast tree reactions to wind, snow, and similar stresses. Should dead wood subtly reshape during the day, existing models might require adjustment, particularly where humidity swings dramatically.

Conducted together with the Finnish Geospatial Research Institute (FGI), the project merged geoinformatics and remote‑sensing know‑how. This collaboration let the team trial their approach across varied climate conditions, bolstering confidence in the results.

Looking forward, the researchers intend to widen monitoring to broader portions of forest canopies and feed humidity‑driven motion data into extensive ecological models. Doing so could sharpen forecasts of forest stability in climate‑change contexts, where shifting humidity may influence the mechanical traits of both living and dead plant matter.