Skip Navigation

Forestry 1988 61(1):29-43; doi:10.1093/forestry/61.1.29
© 1988 by Institute of Chartered Foresters
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by BLACKBURN, P.
Right arrow Articles by MILLER, K. F.
Right arrow Search for Related Content
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

An Assessment of the Static and Dynamic Factors Involved in Windthrow

P. BLACKBURN1, J. A. PETTY1 and K. F. MILLER2 *

1Department of Forestry, University of Aberdeen, St Machar Drive, Aberdeen Scotland AB9 2UU
2Forestry Commission Northern Research Station, Roslin, Midlothian Scotland EH25 9SY

Static parameters of the windthrow process were measured by winching over ten Sitka spruce trees growing on a windthrow-susceptible site in the Scottish Borders. The critical wind speeds to cause uprooting were calculated using measured wind profiles and assuming static loading of the crown. Values obtained greatly exceeded the wind speeds recorded during a gale which caused damage. The ranking of stabilities of the ten samples was: Suppressed trees >gt; sturdy dominants >gt; slender dominants. Recalculation using measured damping ratios, and assuming that the gust frequency coincided with the tree frequency to cause resonance, reduced the values to within the range of the maximum recorded gust.

Displacements of three sample trees, estimated from accelerometer data, were compared with simultaneous wind speed recordings. Perfect resonance was not observed but large oscillations built up over a period of 2–3 cycles. Estimates of the dynamic load factors varied from 0.5–5. The larger gusts tended to be associated with the smaller factors. Increasing the dynamic load factor from 1 (equivalent to a static load) to 2 reduced the critical wind speed by approximately 40 per cent.

The influence of sway direction and canopy contact on the damping ratio of the three accelerometer trees was investigated. The results suggest that canopy contact comprises a greater portion of the damping ratio of small trees than that of dominants.


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?


This article has been cited by other articles:


Home page
 ForestryHome page
M. J. WOOD, R. Scott, P. W. Volker, and D. J. Mannes
Windthrow In Tasmania, Australia: Monitoring, Prediction And Management
Forestry, July 1, 2008; 81(3): 415 - 427.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Bot.Home page
F. Bruchert and B. Gardiner
The effect of wind exposure on the tree aerial architecture and biomechanics of Sitka spruce (Picea sitchensis, Pinaceae)
Am. J. Botany, October 1, 2006; 93(10): 1512 - 1521.
[Abstract] [Full Text] [PDF]

Home page
 Am. J. Bot.Home page
K. R. James, N. Haritos, and P. K. Ades
Mechanical stability of trees under dynamic loads
Am. J. Botany, October 1, 2006; 93(10): 1522 - 1530.
[Abstract] [Full Text] [PDF]


Disclaimer:
Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.