Threats to pine stands by the pine shoot beetles Tomicus piniperda (L.) and Tomicus minor (Hart.) (Col., Scolytidae) around a sawmill in southern Poland

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Forest stands growing around sawmills are especially exposed to damage due to the feeding by the pine shoot beetles Tomicus piniperda (L.) and Tomicus minor (Hart.) (Col., Scolytidae) in the pine shoots, causing a considerable loss of increment. The purpose of this study was to determine the relation of the distance zone of a stand from a sawmill to the density of the pine shoot fall, width of annual rings, and pine stand quality. The investigations were carried out between 1992 and 1996 in a Pinus silvestris–Abies alba stand adjacent to a sawmill in the Zagnańsk Forest District. In the investigated stand, eight zones situated at different distances from the sawmill were marked out, in which the fallen pine shoots were collected and dendrometric measurements taken. The study results showed that the pine shoot fall in the area up to 300 m away from the sawmill was significantly greater than the fall in zones situated further away. In addition, the mean current annual and 10‐year radial increments at breast height were significantly smaller, and the pine stand quality class was lower within that area. The radial increment at breast height in the area up to 300 m away from the sawmill was almost twice as low as that in the control area, and about 40% lower than the increment in the area situated 300–900 m away. The increment pattern of pine in this area differed from that of fir, suggesting that the incremental loss and lower pine stand quality are the result of long‐term feeding of the pine shoot beetles in the pine shoots. These results indicate that other causes, such as differences in site class, climatic factors or air pollution, can be excluded.