YIELDS OF NORWAY SPRUCE (PICEA-ABIES (L) KARST) IN 2 CONSECUTIVE ROTATIONS IN SOUTHWESTERN SWEDEN

Comparisons were made between consecutive generations of Norway spruce (Picea abies (L.) Karst.) in southwestern Sweden. The data analysed were obtained from recordings made on permanent sample plots established initially to compare the effects of different management regimes on yield. Measurements on the plots were made at short intervals, resulting in an uninterrupted time series. First- and second-generation growth refers mainly to growth occurring from 1880 to 1919 and from 1950 to 1989, respectively. In total, 22 observation units are from first-generation stands and 17 are from second-generation stands. The plots are located in a very homogenous area of about 100 ha that has been forested for hundreds of years. On average, the total volume yield from 0-40 years of age in the second-generation stand was 40% higher, than that in the first-generation stand. In addition, dominant-tree height at a stand age of 40 years was about 20% greater in the second generation. Many factors are likely to have contributed to the increase in forest productivity. One of the most important is probably the increase in nitrogen deposition that has occurred since 1950 in southwestern Sweden.