Full scale testing of tree streamlining in wind (STREEM)

• Applicants: Professor Dr.-Ing. Alexander Reiterer; Professor Dr. Dirk Schindler
• Subject Area: Forestry
• Term: from 2021 to 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 460531546

• Final Report Year: 2025

Final Report Abstract

In the STREEM project, wind energy transfer to trees and their response were analyzed using a distributed system of cameras, tilt sensors, and strain sensors. The aim was to quantify energy transfer at the crown periphery and its dissipation within the tree down to the roots. Although it was not possible to quantify wind-induced crown deformation to derive changes in the projected crown area, drag coefficient, and crown porosity, significant insights into windtree interactions were gained. In forests, costly wind speed measurements can be replaced or supplemented by inexpensive air pressure measurements. This method enables measurements in complex terrain, where setting up measurement towers is often neither feasible nor cost-effective. Using the effective wind load concept, the wind-induced tree response was calibrated with pulling tests, establishing a connection between tree-specific reactions and quasi-static wind loads, which primarily govern wind-induced tree reactions. The Tree Strain Sensor (TSS) complemented the Tree Motion Monitoring System (TreeMMoSys) and, for the first time, enabled continuous measurement of wind-induced tree response from the crown to the roots. Measurements on a freestanding European beech showed that the transferred flow energy is primarily distributed in the first bending vibration mode. The previously assumed exchange of elastic energy between different vibration modes was not confirmed. Higher bending vibration modes play a minor role in energy dissipation, and the sway measurement signal energy decreases linearly by 90 % from the crown to the roots. Studies on a ponderosa pine revealed that, in addition to bending, torsional vibrations also occur in trees but decrease significantly as wind load increases. Furthermore, a multi-camera system was developed to track targets within tree crowns. The findings from STREEM significantly enhance the understanding of wind-tree interactions and provide valuable input for the development of wind load models and the assessment of the stability of forest and urban trees.

Link to the final report

https://doi.org/10.4126/FRL01-006511922

Publications

• The motion of trees in the wind: a data synthesis. Biogeosciences, 18(13), 4059-4072.
  Jackson, Toby D.; Sethi, Sarab; Dellwik, Ebba; Angelou, Nikolas; Bunce, Amanda; van Emmerik, Tim; Duperat, Marine; Ruel, Jean-Claude; Wellpott, Axel; Van Bloem, Skip; Achim, Alexis; Kane, Brian; Ciruzzi, Dominick M.; Loheide II, Steven P.; James, Ken; Burcham, Daniel; Moore, John; Schindler, Dirk; Kolbe, Sven ... & Gardiner, Barry
  
• TreeMMoSys: A low cost sensor network to measure windinduced tree response. Forstwissenschaftliche Tagung (FowiTa) unter dem Motto: Wald: wie weiter?, 13.–15.09.2021, Online-Tagung
  Kolbe, S. & Schindler, D.
  
• Assessment of Effective Wind Loads on Individual Plantation-Grown Forest Trees. Forests, 13(7), 1026.
  Kolbe, Sven; Rentschler, Felix; Frey, Julian; Seifert, Thomas; Gardiner, Barry; Detter, Andreas & Schindler, Dirk
  
• Enhancing TreeMMoSys with a high-precision strain gauge to measure the wind-induced response of trees down to the ground. HardwareX, 12, e00379.
  Nickl, Julius; Kolbe, Sven & Schindler, Dirk
  
• On the Potential of Using Air Pressure Fluctuations to Estimate Wind-Induced Tree Motion in a Planted Scots Pine Forest. Forests, 13(2), 225.
  Kolbe, Sven; Mohr, Manuel; Maier, Martin; Osterholt, Laurin; Gardiner, Barry & Schindler, Dirk
  
• Excessive monitoring of wind-induced tree response using TreeMMoSys. Vortrag, 10th IUFRO Conference Wind and Trees 2023, 20.-23.06.2023, Castelfranco Veneto
  Kolbe, S., Kammel, F., Reiterer, A., Schmitt, A. & Schindler, D.
  
• Using air pressure fluctuations for wind load estimation. Poster, Wind and Trees 2023 Conference, 20.-23.06.2023, Castelfranco Veneto
  Kolbe, S. & Schindler, D.
  
• Wind-induced tree response consists not only of bending vibrations – there are also torsional vibrations. Vortrag, Wind and Trees 2023 Conference, 20.- 23.06.2023, Castelfranco Veneto
  Schindler, D. & Kolbe, S.
  
• Conceptualization and First Realization Steps for a Multi-Camera System to Capture Tree Streamlining in Wind. Forests, 15(11), 1846.
  Kammel, Frederik O. & Reiterer, Alexander
  
• Identifying wind-tree dynamics with numerical simulations based on experimental modal analysis. Forest Ecology and Management, 569, 122188.
  Zanotto, Francesco; Grigolato, Stefano; Schindler, Dirk & Marchi, Luca
  
• Mode coupling and signal energy distribution in an open-grown European beech tree. Forest Ecology and Management, 560, 121845.
  Kolbe, Sven; Kammel, Frederik; Schmitt, Annette; Reiterer, Alexander & Schindler, Dirk
  
• Wind-induced torsional vibration in a ponderosa pine tree. Forest Ecology and Management, 553, 121638.
  Kolbe, Sven; Pfenning, Mattis & Schindler, Dirk
  
• The future is uncertain: Wind resilient forests in a changing climate. Forest Ecology and Management, 581, 122556.
  Gardiner, Barry; Lingua, Emanuele; Costa, Maximiliano; Chen, Yi-Ying; Kamimura, Kana; Bunce, Amanda & Schindler, Dirk