Growth and needle retention of Scots pine trees in the region of oil shaleindustry

The long-term impact of air pollutants emitted by oil shale industry on gro wth and needle retention in Scots pine (Pinus sylvestris L) was examined at Kose, in the middle of the North-East Estonian industrial region. Control trees were chosen in a stand growing at Lehtmetsa, North Estonia, 130 km fr om Kose. Ar both sites, ten pine trees were felled and analysed for the hei ght and radial growth rate, and needle retention by using the needle trace method. During the period of 1964-1997, the average height increment of the trees was 47 and 37 cm yr(-1) (P < 0.001) and the average radial increment 2.11 and 0.93 mm yr(-1) (P < 0.001) at Kose and Lehtmetsa respectively. Th e mean needle age was 2.0 and 2.1 years (P = 0.06), the mean number of need les on newly sprouted shoots was 266 and 228 (P<0.001), and the average nee dle density was 5.9 and 9.1 cm(-1) (P < 0.001) at Kose and Lehtmetsa, respe ctively. Changes in concentrations of neither fly ash nor SO2 caused variat ions in the growth of trees and needle retention at Kose.