Tree shape and resistance to uprooting: A simple model analysis
2014
Shibuya, M. (Hokkaido University, Sapporo (Japan). Research Faculty of Agriculture) | Koizumi, A. | Torita, H.
We examined tree resistance to uprooting in relation to tree shape using a simple, qualitative model for the ratio of the resistive moment to the overturning moment. For this analysis, we used model trees and varied the crown size for a fixed stem size for a ratio of crown mass to stem mass that varied from 0.1 to 1. The results predicted the phase transition in the resistance trend in relation to the crown mass/stem mass ratio. Resistance increased on both sides of the crown mass/stem mass ratio, and was minimized at intermediate ratios. This indicates that crown expansion contributes to resistance to the right side of minimum, and vice versa. The same trend was recognized for actual Sitka spruce tree data. These results were consistent with previous observations of tree resistance to uprooting: trees with a small slenderness ratio (ratio of height to diameter at breast height) are resistant to uprooting, and trees/stands are vulnerable to uprooting after thinning, especially after belated thinning. We recommend sparse tree densities in plantations to manage the risk of physical tree damage such as overturning and stem failure. However, quantitative analyses of wind damage to trees and stands are necessary to improve risk management of plantations. The results of this study can be incorporated into such quantitative analyses.
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