Acta Scientiarum Polonorum
Silvarum Colendarum Ratio et Industria Lignaria

Abstract During the years 1998-2002 in investigated forests of southern Poland 99 lightning gaps with 1265 damaged trees as a result of thunder strike were recorded. Among them 99 trees were directly struck by lightning. The lightning gaps were formed in different forest types, mainly in age of VI and V class (74%) as well as in I and II classes of stand quality classification (70%). The lightning gaps appeared most frequently in very strong slope area (slope 18-30°) (39%) at the southern and northern exposition (74%) and at elevation 301-700 m a.s.l. (45% of cases). Beside the damages of single trees, directly struck by lightning, the neighboring trees were also damaged on 64% of lightning gaps (A type). Those, were formed mainly in Norway spruce stands and in forests with the domination of spruce. Among trees species the most frequently damaged was spruce (59% of cases). Damages of a single tree, directly struck by lightning, were evidenced only on 36% of lightning gaps (B type). The lightning gaps B type were formed mainly in fir stands and in forest with the domination of fir. The most frequently struck by lightning tree species was fire (69% gaps B type). Using the statistical Principal Component Analysis (PCA) were shown the multidimensional significant relationships between different distinguished parameters, as: the type of tree stand, elevation, exposition, and site humidity. The relationship between frequency of all lightning gaps and gaps A type and environmental parameters was not present. However, the frequency of gaps B type was primary connected with elevation 301-700 m a.s.l., northern exposition, very strong slope of area, brown soil, age of tree stand within V-VI class and enhanced humidity of site (PCA-1). Next, it was connected with the presence of fir in tree stand (PCA-2).