Production potential of Douglas fir in acid sites of Hurky Training Forest District, Secondary Forestry School in Pisek

The study is a follow-up of the production potential of Douglas fir in mesotrophic sites of the Krtiny Training Forest Enterprise (Journal of Forest Science, No. 7, 2008). Production characteristics (height, dbh, volume) of Douglas fir are also evaluated, but in acid sites of the Hurky Training Forest District, 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 cubic m but the volume of spruce trees was only 1.93 cubic m and the volume of larch trees 2.25 cubic m. Differences between the mensurational variables of Douglas fir and spruce (or larch) were highly significant. At present (based on annual ring analyses), the volume increment of particular Douglas fir trees ranges from 0.06 to 0.10 cubic m/year in mature stands.