Root anchorage and stem strength of black spruce (Picea mariana) trees in regular and irregular stands

• Published in: Forestry (London) Vol. 82; no. 1; pp. 29 - 41
• Main Authors: Bergeron, C., Ruel, J.-C., Élie, J.-G., Mitchell, S.J.
• Format: Journal Article
• Language: English
• Published: Oxford University Press 01.01.2009
• ISSN: 0015-752X; 1464-3626
• DOI: 10.1093/forestry/cpn035

A tree winching experiment was conducted, simulating wind action and resulting damage, in order to assess mechanical resistance of black spruce (Picea mariana (Mill.) B.S.P.) trees in stands of regular and irregular structures. The critical bending moment (Mc) of winched trees was determined and the relationship between Mc and tree and stand characteristics was investigated through statistical analyses. Stem mass (SW), average spacing between trees (S) and height:diameter ratio (H/d.b.h.) were initially selected by a screening procedure to predict Mc. Potential differences between stand structures were tested in mixed models using different subsets of the data. Included fixed effects varied between the different models. SW was the most useful and significant variable in all models and H/d.b.h. was significant only when snapped trees were included in the analysis. When decayed samples were excluded, resistance to uprooting was higher in irregular stands. Decay seemed to play an important role in irregular stands and should be investigated further. Since no difference was observed in the relationship between stem mass and critical turning moment between distant sites, relationships should be applicable across wide regions. This study provides some of the basic relationships required to model windthrow risk in irregular stands. However, the effects of stand structure on wind load for individual trees will also need to be considered.