Effect of half-systematic and systematic thinning on the increment of Scots pine and Norway spruce in Finland |
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| Authors: | Makinen Harri; isomaki Antti; Hongisto Timo |
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| Institution: | 1 Finnish Forest Research Institute, Vantaa Research Centre, PO Box 18, FIN-01301 Vantaa, Finland
2 Metsänhoitoyhdistys Lakeus, Hyypäntie 9, FIN-61800 Kauhajoki, Finland |
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| Abstract: | Diameter, height and volume increment of Scots pine (Pinus sylvestrisL.) and Norway spruce (Picea abies (L.) Karst.) stands wereinvestigated in long-term thinning experiments in southern Finland.The measurement period was on average 19 years, and thinningsconsisted of five different treatments: (1) unthinned; (2) selectivethinning from below where thinning intensity was determinedaccording to the number of stems; (3) selective thinning frombelow where thinning intensity was determined according to standbasal area; (4) systematic thinning where corridors were openedat regular intervals in the stand; and (5) half-systematic thinningwhere corridors were opened at regular intervals and the remainingstrips thinned from below, i.e. a combination of selective andsystematic thinning. The selective (basal area) thinning ofScots pine resulted in a volume growth reduction of about 12per cent, but in Norway spruce it resulted in no marked reductioncompared with the unthinned plots. In both tree species, volumeincrement in the half-systematic and selective (basal area)thinning differed only slightly from each other. The systematicthinning resulted in the lowest volume increment. In the systematicthinning, the total yield (m3 ha–1) somewhat decreasedwith increasing corridor width. In half-systematic thinning,on the other hand, the total yield was not clearly related tocorridor width. A corridor accelerated the diameter incrementof the edge trees. The edge effect progressively diminishedwhen moving deeper into the strip and ended at a distance ofabout 3–4 m from the corridor edge. After the thinning,the height increment first decreased, but later on it recovered.The unthinned plots had more dead trees than the other treatments,but there were no significant differences between the othertreatments. It can be concluded that the prevailing thinningmethod in the Nordic countries, i.e. half-systematic thinning,most probably results in no significant growth and yield losses. |
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