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Wind & Trees

Healthy trees in open locations seldom fall even in the most extreme wind storms. Open-grown trees do not have to compete for resources, and their constant exposure to weather causes them to develop resistance to storm conditions. Among other factors, they have spreading crowns, bushier branching structure, wider bases and a more tapered trunk shape.

Conversely, trees growing in a closed-canopy situation have to compete for space, light, water and nutrients. In the unmanaged roadside forests of southern New England the are also stressed by pollutants, introduced pets and pathogens, and extreme leaning out over a road or open space. These crowded trees lack the resources or the exposure to develop resistance to wind, and are very susceptible to failure.

UConn forest researchers are monitoring tree sway to better understand the dynamic properties of trees, to quantfy how fast and how far they move, and what factors influence that. They will also investigate the potential for forest management to initiate change in those properties. Forest management will give selected trees access to more resources as well as expose them more to weather and could drive the tree to develop more wind-firm features. This development will first be detectable in the dynamic properties of a tree. The extent to which this development can occur in a mature forest stand, and how long it takes, is of great interest to researchers.

41 trees in 3 Connecticut roadside sites are equipped with sensors tracking their movement in all wind conditions. They were monitored for a year before a forest thinning was initiated, and as of summer 2017 each of the three sites has been thinned and trees continue to be monitored. This research will be a valuable factor in mapping tree risk, and in honing the best practices and forestry prescriptions that are recommended to communities for treatment of roadside forests.

 

Goals & Project Updates

 The purpose of this research is to provide guidance to forest management activities that are intended to improve the stability of forests near utility infrastructure. The goals for this project are to:

  • Determine the dynamic properties (sway frequency and amplitude (distance) of sway) and investigate factors of weather, stand structure and tree architecture that influence these properties. 
  • Thin forests around measured trees according to Stormwise management theory and monitor how dynamic properties of trees changes over a several years. 

As of Spring 2018: 

  • 3 roadside sites are established in Storrs, Orange and Torrington Connecticut. Each represents different forest types and conditions.
  • A meteorological tower was established at each site to monitor wind and temperature conditions concurrent with tree sway measurements. 
  • 41 trees (representing 9 species) have been monitored for a year prior to a forest thinning, and continue to be monitored after. 
    • The Storrs site has been monitored since 2012 and was treated in 2013. Orange was started in 2014 and treated in Spring of 2016. Torrington was started in 2014 and treated in summer of 2016. 
  • A sway frequency analysis has been completed and indicates that the speed with which a tree sways depends primarily on the state of the foliage (on or of), whether the ambient temperature is above or below freezing, and the taper of the stem of the tree. (See the figure below). 

 

Study of Tree Biomechanics and reaction to the wind.


 

did-you-know-trees

  • Connecticut ranks thirteenth in the nation in terms of percent forest cover and fourth in terms of population density
  • 55 percent of Connecticut is currently covered by forest
  • Trees in wetlands, rocky or shallow soils have shallow roots and are more susceptible to uprooting.
  • Trees grown in unmanaged forest conditions tend to be tall and slender and susceptible to damage when exposed to wind.
  • Trees in a forest are sheltered by neighboring trees and typically have less wind exposure than open grown trees.
  • Trees along a forest edge are unsheltered and have high potential for wind exposure.
  • Trees along a new or recently trimmed forest edge may be less stable until they adjust to the increased wind exposure.
  • Trees along a forest edge grow toward the open space and so tend to have severe leans and lopsided crowns with reduced stability.
  • Compared to trees that are grown in crowded conditions, trees that have room will grow larger trunks and symmetrical crowns which improves stability and wind resistance.
  • The form of a tree can affect its stability – leans or lopsided crowns make a tree less storm-resistant.

Team Members

Dr. John C. Volin, Vice Provost for Academic Affairs & Professor in the Natural Resources and the Environment department, University of Connecticut.

Jason Parent, Assistant Research Professor, Department of Natural Resources and the Environment, University of Connecticut.

David Miller, Professor Emeritus, Department of Natural Resources and the Environment, University of Connecticut.

Amanda Bunce, Graduate Student, Department of Natural Resources and the Environment, University of Connecticut

Thomas Worthley, Associate Extension Professor, Department of Extension, University of Connecticut.

Mark Rudnicki, Department of Forest Resources, Michigan Technological University

 

Contact Information

For more information, please contact Jason Parent (jason.parent@uconn.edu)

Members of the media, please contact Center Manager Malaquias Pena (mpena@uconn.edu) directly.

 

Eversource Energy Center | Innovation Partnership Building: 159 Discovery Drive, Unit 5276, Storrs, CT 06269-5276 | E-Mail: eversourceenergycenter@uconn.edu