Production potential of Douglas fir in acid sites of Hůrky Training Forest District, Secondary Forestry School in Písek

The study is a follow-up of the production potential of Douglas fir in mesotrophic sites of the Křtiny Training Forest Enterprise (TFE) (Journal of Forest Science, No. 7, 2008). Production parameters (height, dbh, volume) of Douglas fir are also evaluated, but in acid sites of the Hůrky Training Forest District, Secondary Forestry School in Písek in mature stands. In total, 17 mixed stands with the proportion of Douglas fir aged 88 to 121 years were assessed. Comparing 10 Douglas fir trees with 10 Norway spruce, Scots pine or European larch trees of the largest volume, higher and generally markedly higher production potential of the introduced Douglas fir was always found in all assessed stands. Groups where the volume of Douglas fir trees was two to three times higher than the volume of spruce, pine or larch were not an exception. For example, in stand 22B10, the mean volume of the 10 largest Douglas fir trees was 6.30 m3 but the volume of spruce trees was only 1.93 m3 and the volume of larch trees 2.25 m3. Differences between the mensurational parameters of Douglas fir and spruce (or larch) assessed by the ANOVA test were statistically highly significant. At present (based on annual ring analyses), the volume increment of particular Douglas fir trees ranges at level of 0.06 to 0.10 m3/year (i.e. about 0.6 m3 to 1.0 m3 per 10 years) in mature stands.