Title: Effects of different thinning and fertilization regimes on the development of Scots pine (Pinus sylvestris (L.)) and Norway spruce (Picea abies (L.) Karst.) stands in long-term silvicultural trials in Sweden; Olika gallrings- och goedslingsregimers effekter paa bestaandsutvecklingen baserat paa laangliggande experiment i tall- och granbestaand i Sverige
Abstract: Results are presented from an extensive series of thinning and fertilization field trials in Scots pine and Norway spruce stands established from 1966 to 1975. In each of four geographical regions of Sweden, one experiment in Scots pine stands, comprising 10-12 replications of randomized blocks, was established with five to nine different obligatory thinning and/or fertilization treatments. In each of the two southern-most regions, a corresponding experiment was established in Norway spruce stands with nine obligatory treatments. Two/three treatments represent thinnings, of variable intensity, from below. Between one and six thinnings were carried out over the rotation, and the thinning grade varied from 0 to 75 per cent of the basal area before thinning. Recurrent thinnings from above have been studied in one treatment. In two other treatments, thinnings from below was combined with repeated applications of nitrogen and nitrogen plus phosphorus respectively. In the pine stands the current annual volume increment after thinning was negatively and significantly correlated with the intensity of the thinning from below. In the spruce stands a reduction in the current volume growth after thinning from below only occurred in treatments where the thinning rate exceeded 40 per cent of the basal area before thinning. The extreme recurrent thinnings from above have not reduced the volume growth in the pine stands compared with the increment after a conventional thinning from below of the same intensity. A slight reduction of increment, averaging 6 per cent, was found in the spruce stands after as many as five thinnings from above. A significant increase in volume increment of the pine stands was found in both treatments where fertilizers were supplied at regular intervals. The increase was highest in middle Sweden and lowest in the southern part. Spruce stands did not show any volume-increment response to fertilization in either middle or southern Sweden. The site indices for the spruce blocks were, on average, around 32 m according to the Swedish system for site quality assessment. The self-thinned volumes in the unthinned stands of both Scots pine and Norway spruce increased with the length of the observation period. The volume of naturally thinned stems was found to be positively correlated with the stem number and the top height at the time of the establishment of the experiment, which was 12-15 m. It was shown that the pattern of change in top height development was influenced by the intensity of the low-thinning treatments in Scots pine stands but not in the Norway spruce. Nitrogen fertilization caused the top height growth to increase in the pine stands. In the spruce stands, on the other hand, nitrogen fertilization tended to negatively affect top height development. Changes of the stem-diameter frequency distribution in the different treatments were analysed. Averages are presented for the arithmetic mean diameters, the diameter variances and the coefficents of both the asymmetry and the kurtosis. The report does not provide analyses of the economic outcomes of the different treatments in the experimental series, basic information concerning present and future thinning costs, future prices of different assortments and interest rates With 9 page summary in English. 142 refs, 10 figs, 32 tabs
Publication Year: 1997
Publication Date: 1997-12-31
Language: en
Type: article
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