Journal of the Japan Society of Erosion Control Engineering
Online ISSN : 2187-4654
Print ISSN : 0286-8385
ISSN-L : 0286-8385
Research Notes
Resistance force of laterally spread tree roots-lateral root modeling
Atsuhiko KINOSHITAYusuke SAKAIRyoichi OHNOSaburo TABATAMasateru KAWASHIMATakanari YAMASAKI
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JOURNAL OPEN ACCESS

2013 Volume 65 Issue 5 Pages 35-40

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Abstract

Tree roots with an underground lateral network play a very important role in slope stability. Since failures occur in three dimensions, lateral roots fully demonstrate their resistance against failure. This paper describes the resistance force that Δ C lateral roots provide. Intensive field investigations and a model description were made. Since the field data show that the root strength Δ C varies considerably among the surveyed plots, predicting the Δ C from the plot information such as tree species, tree ages, slope and soil thickness can be difficult. To assist with prediction, this paper proposes a Δ C model to calculate the resistance force shown by trees of any age when it is given information about the species, forest operation history, and initial tree density. The Δ C model constitutes four components : a forest yield calculation table ; Karizumi's root volume regression curve ; a root distribution model proposed by Tsukamoto ; and a summation process of Δ C. The model highlights the importance of a particular parameter, which is the weight ratio of lateral roots to full roots. The model shows that the ratio of lateral roots directly affects the size of Δ C. By inspecting the field investigation data and the output of the Δ C model, it has been proved that the change of Δ C over time is well represented by a simple logarithmic curve which has only one coefficient multiplied by the logarithmic term itself. In comparing logarithmic curves to the output of the Δ C model, the logarithmic coefficient corresponds well to the weight ratio of lateral roots. The variance of Δ C shown by the field data is lumped into the coefficient. It has the potential to describe lateral root strength in a simple manner and could be a good index of Δ C. Also, when considering a forest thinning operation, the change in lateral root strength might easily be represented by the coefficient.

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© 2013 Japan Society of Erosion Control Engineering
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