SPATIAL STAND STRUCTURE OF SUGAR MAPLE (ACER-SACCHARUM MARSH) IN ONTARIO, CANADA

In Acer saccharum, the spatial distribution of tree size and individua l response to environmental stress was investigated by means of spatia l autocorrelation. Within 106 mature sugar maple stands in Ontario, Ca nada, traits of 7856 trees were analyzed. Evidence of this study suppo rts the hypothesis that, in old forest stands, trees of similar size a re found in patches. Significant spatial autocorrelation was detected for 57 % of all forest stands for at least one distance class and 25 % of the correlograms indicated non random spatial pattern. As expected , spatial distribution of tree diameter growth was similar to height p atchiness; for 50 % of the maple stands Moran's I-values for one or mo re distance classes and 9% of the spatial correlograms were significan t. Both for height and diameter growth, spatial coefficients were pred ominantly positive for short distances and negative for long distances . Patch size extension for trees having similar size was approximately 15-25 m. Despite non spatial randomness of individual response to env ironmental stress could be anticipated due to certain causes significa nt clusters were not found in sugar maple stands. Rank correlations be tween MORAN's I-values and descriptive stand variables (age, basal are a, height, tree density) were not significant whereas clumping of tree size was more pronounced in stands with less crown closure. For futur e investigations, study sites should comprise approximately 300-400 tr ees. This study shows that spatial autocorrelation analysis can potent ially provide useful information for an enhanced ecological assessment of forest stand development.