A new method is used for evaluation of the tree stability against the wind and for testing the theoretical stability models. The base principle of the uniform couple method is the relative identical environment conditions (site, stand and airflow) by using a couple of one damaged tree and two undamaged trees (the most close). Using the index statistical method it was possible to evaluate the direction of influences of the biometrical and qualitative tree parameters. Height and the ratio between height and diameter of the damaged tree were higher than the same parameters of undamaged trees in 73 % and 83 % of the paars, respectively. The influence of defects, especially the root decay, is the most important in the stability of tree against the wind. Over 50 % of damaged tree have defects. The method of uniform couple is an alter-native to destructive methods for testing, in site condition, by mechanical methods, the stability of tree and to validate the theoretical models.
Keywords: windthrow, uniform couple method, tree stability