Document: MAR-3-69-16

Measure of simultaneous tree sways and estimation of crown interactions among a group of trees.

RUDNICKI, M.* ¹, U.SILINS ¹, V.J.LIEFFERS ¹ and G.JOSI ²

University of Alberta, Edmonton Alberta, Canada ¹
University of Alberta, Edmonton Alberta, Canada ²

Abstract:
We present a technique to measure the simultaneous sway of a group of trees to study the frequency of crown collisions and sway dynamics of individual trees or groups of trees. We placed biaxial clinometers (tiltmeters) at the live crown base in a cluster of ten 15m tall Lodgepole Pine trees near Whitecourt Alberta, Canada. Tree bole rotation at tiltmeter mount height was recorded during windy conditions at a rate of 10 times per second for the cluster of trees. Rotation angles were used in a bole curve shape calculation to estimate tree displacement in 2-dimensional space. Collision reconstruction was done in Arc/Info by assigning asymmetrical crown area dimensions to calculated displacement for each tree. Reconstructions for each time step measures any overlaps between crown areas and outputs the results. Crown overlaps estimated in this manner allow assessment of collision frequencies, area of crown overlap during collisions, and which other trees a subject tree is interacting with. Fifteen minutes of data with an average wind speed of 4.5 m/s, and maximum of 10.0 m/s were processed for an average of 528 collisions and an average collision area of 0.28m². This frequency and depth of collisions supports the notion that wind induced crown interaction inhibits lateral shoot extension and is the dominant mechanism for crown asymmetry and crown shyness. This insight into dynamic crown interactions will allow estimation of and cultivation of forest stand structural attributes that are resistant to damage from wind.

Keywords: Wind, crown collision, tree sway, lodgepole pine, crown assymetry, crown abrasion

This abstract is being presented at: 10:15 AM in session:
Oral Session #42: Disturbance Ecology: Effects of Storms.