The structural integrity of wood can be quantified as resistance to impact milling (RIM). In a High-energy multiple impact (HEMI) – test steel balls were used in a heavy vibratory mill for crushing wood samples. Thousands of single events were captured by analyzing the fragments. Based on the degree of integrity I and the percentage of fine fragments F (< 1 mm) an indicator has been defined to detect structural changes on cell wall level with high sensitivity. The method has earlier been used to detect changes in structural integrity which were caused by chemicals, thermal energy, radiation and different organisms.
Little, however, is known about the within species variation of the degree of integrity, the percentage of fine fragments and the resistance to impact milling. It was therefore the aim of this study to investigate the within species variation of these measures on 204 Scots pine (Pinus sylvestris L.) trees from Northern Europe and see whether wood properties or growth conditions influence the structural integrity.
Significant differences between stands were found for the degree of integrity. Linear mixed models showed that for the degree of integrity, the variance was distributed to 30.6 % on stand variance and 69.4 % on residual variance between trees. Annual height increment and slenderness coefficient could reduce the total variance by roughly 10%, and it was the stand variance which was reduced in both cases. With the data available, it was only possible to reduce the variance between stands, while the variance between trees remained unchanged.
It still remains unclear which wood inherent factors influence degree of integrity, the percentage of fine fragments and the resistance to impact milling. RIM – as a function of both, F and I – turned out to be almost unaffected by wood property variations within the species Pinus sylvestris. It is possible, that these measures are influenced by the anatomical and chemical structure and composition of the wood.
Keywords: high-energy multiple impact (hemi) tests, structural integrity, within species variation, scots pine, wood growth indicators
Authors
Zimmer K.
Norwegian Institute for Bioeconomy Research, Ås, Norway
Brischke C.
Leibniz University Hannover, Faculty of Architecture and Landscape Sciences, Institute of Vocational Sciences in the Building Trade, Hannover, Germany
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