An architectural understanding of natural sway frequencies in trees
Jackson, T. ; Shenkin, A. ; Moore, J. ; Bunce, A. ; Emmerik, T. Van; Kane, B. ; Burcham, D. ; James, K. ; Selker, J. ; Calders, K. ; Origo, N. ; Disney, M. ; Burt, A. ; Wilkes, P. ; Raumonen, P. ; Gonzalez De Tanago Menaca, J. ; Lau, A. ; Herold, M. ; Goodman, R.C. ; Fourcaud, T. ; Malhi, Y. - \ 2019
Journal of the Royal Society, Interface 16 (2019)155. - ISSN 1742-5689 - 9 p.
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.
Finite element analysis of trees in the wind based on terrestrial laser scanning data
Jackson, T. ; Shenkin, A. ; Wellpott, A. ; Calders, K. ; Origo, N. ; Disney, M. ; Burt, A. ; Raumonen, P. ; Gardiner, B. ; Herold, M. ; Fourcaud, T. ; Malhi, Y. - \ 2019
Agricultural and Forest Meteorology 265 (2019). - ISSN 0168-1923 - p. 137 - 144.
Critical wind speed - Finite element analysis - Resonant frequency - Terrestrial laser scanning - TLS - Wind damage
Wind damage is an important driver of forest structure and dynamics, but it is poorly understood in natural broadleaf forests. This paper presents a new approach in the study of wind damage: combining terrestrial laser scanning (TLS) data and finite element analysis. Recent advances in tree reconstruction from TLS data allowed us to accurately represent the 3D geometry of a tree in a mechanical simulation, without the need for arduous manual mapping or simplifying assumptions about tree shape. We used this simulation to predict the mechanical strains produced on the trunks of 21 trees in Wytham Woods, UK, and validated it using strain data measured on these same trees. For a subset of five trees near the anemometer, the model predicted a five-minute time-series of strain with a mean cross-correlation coefficient of 0.71, when forced by the locally measured wind speed data. Additionally, the maximum strain associated with a 5 ms−1 or 15 ms-1 wind speed was well predicted by the model (N = 17, R2 = 0.81 and R2 = 0.79, respectively). We also predicted the critical wind speed at which the trees will break from both the field data and models and find a good overall agreement (N = 17, R2 = 0.40). Finally, the model predicted the correct trend in the fundamental frequencies of the trees (N = 20, R2 = 0.38) although there was a systematic underprediction, possibly due to the simplified treatment of material properties in the model. The current approach relies on local wind data, so must be combined with wind flow modelling to be applicable at the landscape-scale or over complex terrain. This approach is applicable at the plot level and could also be applied to open-grown trees, such as in cities or parks.
|Stochastic simulation of fruit set in sweet pepper
Wubs, A.M. ; Bakker, M.J. ; Heuvelink, E. ; Hemerik, L. ; Marcelis, L.F.M. - \ 2008
In: Plant growth modelling and applications / Fourcaud, T., Zhang, X.P., Los Alamitos, California, USA : IEEE computer society - ISBN 9780769528519 - p. 40 - 47.
|New rule-based modelling methods for radiation and object avoidance in virtual plant canopies
Buck-Sorlin, G.H. ; Hemmerling, R. ; Kniemeyer, O. ; Burema, B.S. ; Kurth, W. - \ 2007
In: Plant Growth Modeling and Applications: Second International Symposium on Plant Growth Modeling, Simulation, Visualisation and Application, Beijing, China, November 13-17, 2006. - Los Alamitos : IEEE - ISBN 9780769528519 - p. 22 - 25.
As an extension of the L-system formalism, relational growth grammars (RGG) can be expressed in the programming language XL, allowing for a transparent specification of structural botanical rules, dependency on the environment and process-based models, all in the same framework. We demonstrate this at simple models for growth under the constraints of object avoidance and sensitivity to radiation
|Concepts to model growth and development of plants
Vos, J. ; Heuvelink, E. - \ 2007
In: Plant Growth Modeling and Applications: Second International Symposium on Plant Growth Modeling, Simulation, Visualisation and Application, Beijing, China, November 13-17, 2006. - Los Alamitos : IEEE - ISBN 9780769528519 - p. 3 - 10.