Determinants of tree sway frequency in temperate deciduous forests of the Northeast United States

Bunce, Amanda; Volin, John C.; Miller, David R.; Parent, Jason; Rudnicki, Mark

doi:10.1016/j.agrformet.2018.11.020

Cited by 29 publications

(35 citation statements)

References 74 publications

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“…Our modelling work shows that tree architectural information can increase the predictability of f 0 by approximately 40% for temperate and tropical forest broadleaf trees. In deciduous forests, the presence of leaves caused an 18% increase in f 0 and a doubling of damping efficiency, which is similar to previous studies [22,46,47]. This increase in f 0 was due to the weight of the leaves, rather than the increased aerodynamic damping.…”

Section: Beyond the Cantilever Beam Approximationsupporting

confidence: 88%

An architectural understanding of natural sway frequencies in trees

Jackson

Shenkin

Moore

et al. 2019

J. R. Soc. Interface.

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The relationship between form and function in trees is the subject of a longstanding debate in forest ecology and provides the basis for theories concerning forest ecosystem structure and metabolism. Trees interact with the wind in a dynamic manner and exhibit natural sway frequencies and damping processes that are important in understanding wind damage. Tree-wind dynamics are related to tree architecture, but this relationship is not well understood. We present a comprehensive view of natural sway frequencies in trees by compiling a dataset of field measurement spanning conifers and broadleaves, tropical and temperate forests. The field data show that a cantilever beam approximation adequately predicts the fundamental frequency of conifers, but not that of broadleaf trees. We also use structurally detailed tree dynamics simulations to test fundamental assumptions underpinning models of natural frequencies in trees. We model the dynamic properties of greater than 1000 trees using a finite-element approach based on accurate three-dimensional model trees derived from terrestrial laser scanning data. We show that (1) residual variation, the variation not explained by the cantilever beam approximation, in fundamental frequencies of broadleaf trees is driven by their architecture; (2) slender trees behave like a simple pendulum, with a single natural frequency dominating their motion, which makes them vulnerable to wind damage and (3) the presence of leaves decreases both the fundamental frequency and the damping ratio. These findings demonstrate the value of new three-dimensional measurements for understanding wind impacts on trees and suggest new directions for improving our understanding of tree dynamics from conifer plantations to natural forests.

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Section: Beyond the Cantilever Beam Approximationsupporting

confidence: 88%

An architectural understanding of natural sway frequencies in trees

Jackson

Shenkin

Moore

et al. 2019

J. R. Soc. Interface.

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“…We collated data from 20 studies that included 238 trees and more than 1 million hours of tree motion data at resolutions ranging from 4 to 20 Hz. These studies used three types of sensor: (1) strain gauges which measure the bending strains at the base of the tree (Moore et al, 2005) (2) inclinometers measuring the changing inclination angle of the trunk (Bunce et al, 2019;Schindler et al, 2010) and 3accelerometers measuring the acceleration at the top of the trunk (Van Emmerik et al, 2017). We refer to these in general as measures of tree deflection.…”

Section: Description Of the Datamentioning

confidence: 99%

“…Additionally, a tree's 0 has been observed to change over time in response to variations in tree mass and elasticity. These changes can be used as a proxy to measure phenology (Bunce et al, 2019;Gougherty et al, 2018) and water status of trees (Ciruzzi and Loheide, 2019) at high time resolution (e.g. every 10 minutes or hour) using low-cost sensors.…”

Section: Introductionmentioning

confidence: 99%

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The motion of trees in the wind: a data synthesis

Jackson¹,

Sethi²,

Dellwik³

et al. 2020

Preprint

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Abstract. 1. Interactions between wind and trees control energy exchanges between the atmosphere and forest canopies. This energy exchange can lead to the widespread damage of trees and wind is a key disturbance agent in many of the world’s forests. However, most research on this topic has focused on conifer plantations, where risk management is economically important, rather than broadleaf forests, which dominate the forest carbon cycle. This study brings together all available tree motion time-series data to systematically evaluate the factors influencing tree responses to wind loading, including data from both broadleaf and coniferous trees in forests and open environments. 2. We found that the two most descriptive features of tree motion were: (a) the fundamental frequency, which is a measure of the speed at which a tree sways and is strongly related to tree height, and (b) the slope of the power spectrum, which is related to the efficiency of energy transfer from wind to trees. Intriguingly, the slope of the power spectrum was found to remain constant from medium to high wind speeds for all trees in this study. This suggests that, contrary to some predictions, damping or amplification mechanisms do not change dramatically at high wind speeds and therefore wind damage risk is related, relatively simply, to wind speed. 3. Conifers from forests were distinct from broadleaves in terms of their response to wind loading. Specifically, the fundamental frequency of forest conifers was related to their size according to the cantilever beam model (i.e. vertically distributed mass), whereas broadleaves were better approximated by the simple pendulum model (i.e. dominated by the crown). Forest conifers also had a steeper slope of the power spectrum. We interpret these finding as being strongly related to tree architecture, i.e. conifers generally have a simple shape due to their apical dominance, whereas broadleaves exhibit a much wider range of architectures with more dominant crowns.

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“…Fundamental vibrational frequencies (f n ) were collated from the literature on field studies of 703 broadleaf and conifer trees growing at different sites and under different conditions, spanning height and DBH ranges of 5.9-35.4 m and 6.9-82.8 cm, respectively [11,12,15,28,31,[48][49][50][51][52][53]. These field data were used to validate the tapered cantilever beam model and provide further fundamental understanding of the sway behaviour of conifer and broadleaf trees.…”

Section: Estimating Natural Frequency For Coniferous and Broadleaved mentioning

confidence: 99%

A Numerical Approach to Estimate Natural Frequency of Trees with Variable Properties

Dargahi

Newson

Moore³

2020

Forests

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Free vibration analysis of a Euler-Bernoulli tapered column was conducted using the finite element method to identify the vibration modes of an equivalent tree structure under a specified set of conditions. A non-prismatic elastic circular column of height L was analysed, taking distributed self-weight into account. Various scenarios were considered: column taper, base fixity, radial and longitudinal stiffness (E) and density (ρ) and crown mass. The effect on the first natural frequency was assessed in each case. Validation against closed form solutions of benchmark problems was conducted satisfactorily. The results show that column taper, base fixity and E/ρ ratio are particularly important for this problem. Comparison of predictions with field observations of natural sway frequency for almost 700 coniferous and broadleaved trees from the published literature showed that the model worked well for coniferous trees, but less well for broadleaved trees with their more complicated crown architecture. Overall, the current study provides an in-depth numerical investigation of material properties, geometric properties and boundary conditions to create further understanding of vibration behaviour in trees.

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Determinants of tree sway frequency in temperate deciduous forests of the Northeast United States

Cited by 29 publications

References 74 publications

An architectural understanding of natural sway frequencies in trees

An architectural understanding of natural sway frequencies in trees

The motion of trees in the wind: a data synthesis

A Numerical Approach to Estimate Natural Frequency of Trees with Variable Properties

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