Quantifying the effects of freezing on tree sway frequencies

Abstract Wind induced sway was measured for 18 conifers in an even aged, naturally regenerated evergreen forest in Howland, ME between August 23, 2009 and January 29, 2010. Tree sway was measured using biaxial clinometers and wind speed, wind direction and temperature were measured using sonic anemometers, with all measurements at 10 Hz. This study quantifies changes in wind-loaded tree-sway frequencies for frozen and unfrozen stems. A tree's sway frequency significantly changes as freezing conditions change its material properties by increasing flexural stiffness. This study found that sway frequencies of frozen trees are increased by 27.9%, but frozen trees loaded with snow only exhibit an increase of 9.4%. The effects of atmospheric stability were also considered and were found to have no statistically significant effect on tree sway frequency. Datasets (30 min in duration) were chosen when the hourly average of wind speed was >2 m/s above the canopy. Three conditions were considered in the analysis of the data, one with temperatures well above freezing (>5 °C) one with freezing temperatures (

[1]  Victor J. Lieffers,et al.  Stand structure governs the crown collisions of lodgepole pine , 2003 .

[2]  Douglas A. Maguire,et al.  Natural sway frequencies and damping ratios of trees: concepts, review and synthesis of previous studies , 2004, Trees.

[3]  B. Gardiner,et al.  Wind and Trees: The interactions of wind and tree movement in forest canopies , 1995 .

[4]  X. Lee,et al.  Nocturnal mixing in a forest subcanopy , 2000 .

[5]  R. Milne,et al.  Dynamics of swaying of Picea sitchensis. , 1991, Tree physiology.

[6]  E. D. Langre,et al.  Modelling waving crops using large-eddy simulation: comparison with experiments and a linear stability analysis , 2010, Journal of Fluid Mechanics.

[7]  Uldis Silins,et al.  The effect of temperature on mechanical properties of standing lodgepole pine trees , 2000, Trees.

[8]  E. D. Langre.  Effects of Wind on Plants , 2008 .

[9]  Vincent A. Webb,et al.  A Linear Analysis of the Interaction Between the Atmosphere and an Underlying Compliant Plant Canopy , 2009 .

[10]  M. J. Jaffe,et al.  Morphogenetic Responses of Plants to Mechanical Stimuli or Stress , 1980 .

[11]  B. Gardiner,et al.  Management of forests to reduce the risk of abiotic damage — a review with particular reference to the effects of strong winds , 2000 .

[12]  B. Amiro,et al.  Pressure Fluctuations during Coherent Motions and Their Effects on the Budgets of Turbulent Kinetic Energy and Momentum Flux within a Forest Canopy , 1994 .

[13]  N. Haritos,et al.  Mechanical stability of trees under dynamic loads. , 2006, American journal of botany.

[14]  Thierry Fourcaud,et al.  A numerical model of tree aerodynamic response to a turbulent airflow , 2008 .

[15]  B. Gardiner,et al.  Comparison of two models for predicting the critical wind speeds required to damage coniferous trees , 2000 .

[16]  Uldis Silins,et al.  Measure of simultaneous tree sways and estimation of crown interactions among a group of trees , 2001, Trees.

[17]  Bruno Moulia,et al.  A frequency lock-in mechanism in the interaction between wind and crop canopies , 2006, Journal of Fluid Mechanics.

[18]  A. J. G. Papesch,et al.  Wind and its effects on (Canterbury) forests , 1984 .

[19]  Vincent A. Webb,et al.  The periodic motion of lodgepole pine trees as affected by collisions with neighbors , 2008, Trees.

[20]  F. Smith,et al.  Volume increment in Pinus contorta var. latifolia: the influence of stand development and crown dynamics , 1992 .

[21]  Steward T. A. Pickett,et al.  Forest Reorganization: A Case Study in an Old‐Growth Forest Catastrophic Blowdown , 1995 .

[22]  T. Fourcaud,et al.  A finite element model for investigating effects of aerial architecture on tree oscillations. , 2006, Tree physiology.

[23]  R. Stull.  An Introduction to Boundary Layer Meteorology , 1988 .

[24]  Kenneth R. James,et al.  Dynamic Loading of Trees , 2003, Arboriculture & Urban Forestry.

[25]  R. Shaw,et al.  Influence of foliar density and thermal stability on profiles of Reynolds stress and turbulence intensity in a deciduous forest , 1988 .