An experimental investigation of the effects of dynamic loading on coniferous trees planted on wet mineral soils (Chapter 11) - Wind and Trees (original) (raw)

Abstract

Two field studies are presented on the in situ dynamic loading of mature coniferous trees planted on wet mineral soils. The studies consisted of examining the behaviour of a complete tree under natural wind loading and a number of trees with truncated stems under forced dynamic loading. The test site has a history of tree instability and the mineral soil under the rootplates consists of a clayey silty sand. The rootplates of the tested trees were shallow and the main roots had an asymmetrical radial distribution about the tree stem centre. The dynamic loading caused an increase in soil pore water pressure, and in the forced loading tests it led to hydraulic fracturing of the rootplate.

Introduction

Windthrow is a major source of economic loss in Irish and United Kingdom forests and crop instability imposes important restrictions on silviculture. This chapter presents details of two field studies (Rodgers et al., 1990; McMenamin, 1992) on the dynamic loading of mature Sitka spruce trees planted on double mouldboard plough ridges. The objectives of the studies were:

1. To develop a mechanical rocking device and a high-speed data logging system which could be used to assess the stability of trees in the field.
2. To study the behaviour of trees and rootplates subjected to forced dynamic loading.
3. To study the behaviour of a tree under natural storm conditions.
4. To identify soil properties which are important for tree stability.
5. To investigate the stiffness values and Young's moduli of the trees.
6. To monitor the changes in damping that occur during forced dynamic loading.