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Relationship between Douglas fir latewood and some environmental factors Hall, Gavin Siegmund


This study was initiated to determine the importance of various tree characteristics and environmental factors in controlling Douglas fir (Pseudotsuga menziesii (Mirb.) Franco) latewood formation during the five-year period 1957 to 1961. The sample included 324 mature trees representing five site types and four crown classes on the University Research Forest, Haney, B.C. Two wood "plugs" were taken from each tree at approximate breast height. The influence of seasonal variations in precipitation, temperature and frost free days on growth ring characteristics was also examined. Individuals showed significant differences in ring, earlywood and latewood zone width, and latewood percentage. Replicate samples within trees showed smaller differences. Width of earlywood and latewood increased with increasing site moisture; latewood percentage increased with dry and wet to mesic sites, suggesting some unexplained compensating mechanism. Earlywood and latewood widths increased from suppressed to dominant trees when data from all sites were grouped. No significant differences in latewood percentage were shown among crown classes, suggesting that adverse factors affecting the lower classes must influence both zones similarly. Diameter at breast height had the most influence of any tree characteristic studied, but was related to many other tree variables. Crown volume was second in importance, the order of factors being similar for all five sites. Other tree factors investigated were height, competition factor and distance to live crown. When considered in conjunction, the five tree variables accounted for about 55 per cent of the variation in ring, earlywood and latewood width. This varied somewhat with growth and site characteristics. Latewood percentage was explained to the extent of 5 per cent except on the very dry site, where 29 per cent was accounted for, mainly by crown volume and distance to live crown. Correlations with climatic factors were generally poor probably resulting from the equable climate of the area and the absence of extremes during the period studied. Both early and late season precipitation correlated positively with latewood percentage. Temperature generally showed a negative relationship with this variable. The overall dominating influence of available moisture on latewood production was shown.

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