Electronic Journal of Polish Agricultural Universities (EJPAU) founded by all Polish Agriculture Universities presents original papers and review articles relevant to all aspects of agricultural sciences. It is target for persons working both in science and industry,regulatory agencies or teaching in agricultural sector. Covered by IFIS Publishing (Food Science and Technology Abstracts), ELSEVIER Science - Food Science and Technology Program, CAS USA (Chemical Abstracts), CABI Publishing UK and ALPSP (Association of Learned and Professional Society Publisher - full membership). Presented in the Master List of Thomson ISI.
Volume 7
Issue 2
Giefing D. , Jonasz K. , Wesoły W. 2004. THE RESPONSE OF THICK-BRANCHED PINE TREES TO PRUNING, EJPAU 7(2), #03.
Available Online: http://www.ejpau.media.pl/volume7/issue2/forestry/art-03.html


Dieter Franciszek Giefing, Kamila Jonasz, Wojciech Wesoły



The experiments were carried out on pine trees (Pinus sylvetris L.) growing in a seedlings seed orchard. Pine trees were pruned at the following terms: 25th April 1995, 14th July 1995 and 1st March 1996. Each time, trees were pruned (4 whorls of branches were removed) using the four different types of saws. Whereas wounds left after the removal of branches were treated with: emulsion paint, lack-balsam and Funaben and some wounds were left untreated for control purposes (zero treatment).

Key words: Scots pine, pruning, knot, wound cicatrisation, increment..


In the period between the two world wars, in the wake of negative biological results of on-site tree pruning in the forest revealed by some researchers [6, 5, 2, 3], an opinion developed maintaining that pine and spruce pruning of live branches was a harmful operation involving a considerable risk of infection with pathogens. The above opinion, which remained dominant in Europe until 1950s, is still quite widespread and continues to exert a strong influence on the beliefs of some foresters concerning pruning. Pruning instructions developed in the following years allowed pruning of live branches of the above-mentioned tree species, provided that the thickness of these branches did not exceed 2 cm. It should be emphasised here that the above-quoted instructions did not differentiate between pruning principles of these two major coniferous forest-forming tree species, despite the fact that live-wood sensitivities of spruce and pine to infections differ. Spruce wood is very sensitive to infect ions and unprotected, open, bigger wounds usually become infected, in contrast to pinewood, which is known not to yield to infections easily, even in the case of serious injuries (during extraction, tapping of board by game and resin collection). As a rule, their only negative consequence is the development of bark pockets and pitchy wood.

The presented observations and research results concerning the effect of pine pruning of live branches [4, 7, 8] inspired the authors to undertake investigations on biological consequences of pruning pine trees of tick branches. The issue appears to be gaining increasing importance in view of the observed growing interest in wood production employing plantation systems. Tree pruning is an essential tending operation on such plantations allowing production of valuable wood. In addition, feasibility of pine pruning of thick branches can also exert a considerable influence on methods of carrying out tending operations in commercial stands in which wolf trees were not removed in proper time. Intensive pruning of wolf trees eliminates their further negative influence on the surroundings and, at the same time, creates favourable conditions for the production of valuable, knot-free wood.

The objective of the performed investigations was to determine the response of thick-branched pine trees growing in a loosened spacing in plantation conditions to the applied tree pruning operations. Two issues appeared to be particularly interesting: the process of wound healing after branch removal and the risk of infection through such wounds. In addition, the experiment also aimed to assess the increment response of trees to pruning.


The experiments were carried out on pine trees (Pinus sylvetris L.) growing in a seedlings seed orchard situated in the Zdrojowa Góra Division, Regional Direction of State Forests in Piła. The trees (half-sib family) on the plantation were planted in 1984 year at 4.0 x 4.0 m square spacing. This arrangement was loosened in 1994 leaving trees at 8.0 m spacing (Fig. 1). Pine trees were pruned at the following terms: 25th April 1995, 14th July 1995 and 1st March 1996 (Fig.2).

Figure 1. Plantation cultivation of Scots pine (Pinus sylvestris L.) before treatment

Figure 2. Plantation cultivation of Scots pine (Pinus sylvestris L.) immediately after pruning treatment

Each time, trees were pruned (4 whorls of branches were removed) using the following four different types of saws: Dauner, Hengst, Bushman and a German model saw, whereas wounds left after the removal of branches were treated with: emulsion paint, lack-balsam and Funaben (Fig.3) and some wounds were left untreated for control purposes (zero treatment).

Figure 3. A pine tree after a pruning operation with wounds treated with Funaben

In June 2001, eighty-seven knots from 4 test trees were investigated. Each of the examined trees represented a different method of wound protection. It should be mentioned here that, at the moment of examination, the process of knot occlusion was either completely or partially finished (Fig.4).

Figure 4. Partially and completely occluded wounds after the removal of thick branches and visible nodular outgrowths in the place of pruning

In laboratory conditions, a visual evaluation was performed of the condition of the open knot and the diameter of the unhealed wound was measured. Next, using a band saw, logs were cut along the plane: knot axis – bolt axis. The experimental material prepared in this way was used to estimate the health condition of knots and the bolt wood adjacent to them (when estimating the health condition, the authors resigned from the phytopathological assessment of pathogen presence on the assumption that that the presence of a pathogen is not equivalent to the development of the disease. Investigations carried out by Zygmunt Miler and Antoni Miler revealed their widespread presence on the wound surface and, at the same time, a complete absence of pathogenic changes in the wood of trees (MILER, MILER 1980)). In addition, the diameter of the knot without bark, bolt radius as well as the length and width of the bark pocket (if present) were also measured. Finally, the state of the knot occlusion and the time of this process were determined.



The collected experimental material made it possible to assess 87 knots, which were characterised by diameters (knot diameters without bark) ranging from 5 mm to 68 mm, 22.03 mm on average. It should be emphasised here that the thickness of knots given was without bark and the measurements were taken on trunk cross-sections. Bearing in mind the thickness of bark, it can be assumed that the maximum thickness of removed branches exceeded 70 m quite considerably. This assumption was confirmed by results of measurements carried out while performing pruning operations.

A comprehensive analysis of all the 87 knots after their exposure did not show any pathogenic changes of either knot wood or the wood in their vicinity (Fig. 5, 6, 7, 8). This indicated the appropriateness of tree pruning cultivated in a plantation system and pointed to the possibility of utilising the pruning operations to restrict the negative influence of wolf trees on the surrounding stands.

Figure 5. Bark pocket over a blind knot

Figure 6. A cross section through a completely occluded knot of approximately 3 cm diameter, which became occluded in the third year after pruning

Figure 7. A partially occluded, improperly pruned knot

On the other hand, bark pockets were found to occur quire frequently. Open inbarks were found on cross-sections of 23% of the examined knots, while in 63% - they were absent. Obviously, the remaining 14% comprised open knots. There were, usually, small bark pockets of approximately 5 mm thickness. Large bark pockets, which could have a negative impact on the possibility of further wood processing were also observed. However, it should be emphasised that in the case of pruned trees they usually occurred in the area close to the trunk pith area and their size was always many times smaller than the area of damaged knot in self-pruning trees.

Figure 8. Number of occluding wounds after the removal of branches in consecutive years after pruning on a pine seed plantation

In some cases, a minor area of dead knots was observed to occur (Fig, 6, 8) which should not have taken place, given the fact that the trees were pruned from live branches. However, in the course of pruning, branches were cut along the side surface of bark and not wood. Therefore, a segment of the branch “grown into” bark was left uncut. In the case of trees pruned in winter, this segment constituted a fragment of the dead knot. Trees pruned during vegetation, immediately after the removal of a branch, activated tissue adjacent to the wound and, by so doing, initiated the process of cicatrisation. This prevented necrosis of the snag grown into the bark and forestalled the development of a dead knot area.


It is worth reminding here that, in the performed experiment, the pruning was conducted on thick-branched trees with branch diameter frequently exceeding 70 mm. Despite this, five years after trees were pruned, only 14% of open knots were found in the experimental material, while 86% of wounds were completely cicatrised. It should be mentioned here that in the case of pine trees growing in commercial stands, the time of wound cicatrisation after the removal of live branches of approximately 2 cm dimensions ranges from 5 to 7 years [1].

Pine trees growing on plantations under investigations were characterised by very strong increments. The average width of the last 5 annual rings was 5.9 mm and this exerted a significant influence on the dynamics of knot occlusion. Already in the first year after pruning, 27% of wounds became cicatrised (Fig.9). These were, obviously, the smallest knots and their average diameter was 15.04 mm. It is worth mentioning here that, as a rule, the average time of occlusion of such knots in ordinary pine stands ranges from 5 to 7 years - in the case of pruning trees of live branches and up to several years - in the case of the removal of dead branches [1].

Figure 9. Average diameter of knots occluded in consecutive years after tree pruning

In the second year after performing the pruning operation, another 29% of knots with average diameter of 16.36 mm became occluded, while in the third year – another 21%, with average diameter of 22.06 mm (Fig.7). Four years after pruning, 6% of knots with the average diameter of 30.40 mm became completely cicatrised and a year later – 3% more knots with 45 mm diameter became occluded. At the moment of harvesting of test trees, open knots were observed in 14% of them and their average diameter without bark was 38.58 mm. It must be emphasised here that the advance of the process of knot occlusion was two times faster than in commercial stands. In the case of experimental surfaces, more than half of the knots healed their wounds within 2 years from pruning (Fig.9) and after 5 years – 86% of knots were occluded.


Pine trees harvested on plantation surfaces were characterised by considerable annual increments. In the course of pruning, 4 whorls of branches were removed. This led to a considerable reduction of the assimilation apparatus and implied a reduction in the growth of trees following their pruning. However, results of measurements of 3-year increments of block diameters obtained from the pruned part of trees showed that only in 35% of cases, tree increments were greater before than after the treatment and the average drop in the 3-year increment amounted to only 2 mm. On the other hand, in 55% of cases greater increments were found after pruning than before the operation and the extent of the increment dynamism was almost two times greater and amounted to 3.18 mm. No changes in the extent of increment were recorded only in 10% of trees. In 70% of cases, changes in the level of 3-year increments following pruning, when compared with the 3-year period preceding this operation, attained the valu e greater than 1 mm. The greatest increment drop reached 5 mm, whereas the highest gain of increment following the pruning operation was 10 mm. It can, therefore, be said that, as a rule, a trend was observed towards increased diameter increment of trees after the applied pruning operation.

The obtained results corroborate the opinion that when branches are removed from the shaded part of trees, they can respond to this treatment by increased increments, which can be attributed to a negative balance of assimilate production in this part of the tree crown. It can be assumed that the real tree growth increments were even greater because the applied pruning moved upwards maximum tree diameter increments – towards the base of crowns. It should be remembered that measurements were carried out on blocks obtained from the tree trunks deprived of branches.


  1. Thick-branched trees growing in plantation conditions are characterised by a considerable dynamics of the process of wound cicatrisation developed in the result of branch removal in the course of pruning. The time of their occlusion, despite the fact that these wounds are bigger, is shorter than the time required for the occlusion of trees pruned in commercial stands.

  2. The removal of thick branches from pine trees growing in a loosened spacing system on plantations does not pose any serious risk of infection. No pathogenic changes of knots and the adjacent wood were observed following tree pruning irrespective of the season and the applied tools. On the other hand, bark pockets were found to occur almost in every fourth blind knot.

  3. In the majority of the examined cases, pine pruning cultivated in a plantation system increased diameter increment of trees (increased width of annual rings).

  4. The obtained research results point to the possibility of limiting negative influence of wolf trees on stands in the result of their intensive pruning.


  1. Giefing D.F. 1999. Podkrzesywanie drzew w lesie [Pruning of trees in the forest]. A. Cieszkowski Agricultural University in Poznań publication, pp. 168 [in Polish]

  2. Hilf H.H. 1933. Die Erzeugung von Wertholz durch Aufästung des Nadelholzes. [Approval of the wood quality of pruned deciduous trees]. Deutscher Forstverein [in German].

  3. Koehler R. 1934. Trockenästung von Fichtenbestanden [Dead branch pruning of spruce]. Allg. Forst- u. Jagdztg. 110, 1: 7-9 [in German].

  4. Kowalów J. 1977. Wpływ podkrzesywania sosny na zdrowotno¶ć w jej pniach [Effect of pine pruning on health of trunks]. Manuscript. Chair of Forest Utilisation, A. Cieszkowski Agricultural University in Poznań [in Polish].

  5. Lakari O.J. 1920. Untersuchungen über die Astung der Fichte [Research of the spruce pruning]. Commun. Inst. For. Fenn., 2: 1-5 [in German].

  6. Lorey T. 1907. Handbuch der Forstwissenschaft [The hand-book of forest science]. Tübingen, Bd. 1: 528-532 [in German].

  7. Miler Z., Miler A. 1980. Wpływ podkrzesywania na zdrowotno¶ć drewna przyrannego u niektórych gatunków drzew [Effect of pruning on the health condition of wood adjacent to the wound in some tree species]. Papers of the Commission of Agricultural Sciences and Commission of Forest Sciences of the Poznań Society of Friends of Sciences, 40:67-69 [in Polish].

  8. Pazdrowski W. 1992. Zmiany jako¶ci i warto¶ci drewna w drzewostanach sosnowych przy stosowaniu podkrzesywania drzew [Changes of the quality and value of wood in pine stands in which pruning was applied]. Annals of Agricultural University in Poznań, Scientific Dissertations, No. 224 [in Polish].

Dieter Franciszek Giefing, Kamila Jonasz
Department of Forest Utilization
August Cieszkowski Agricultural University in Poznań
60-625 Poznań, ul. Wojska Polskiego 71A
e-mail: giefing@au.poznan.pl

Wojciech Wesoły
Department of Silviculture
August Cieszkowski Agricultural University in Poznań
60-625 Poznań, ul. Wojska Polskiego 71A
e-mail: wesoly@au.poznan.pl

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