CYCLICAL WOOD HETEROGENEITY OF NORWAY SPRUCE PICEA ABIES (L) KARST. ON STEM PROFILES OF TREES FROM DIFFERENT SOCIAL POSITIONS IN STANDS OF AGE CLASS IV

Dieter Franciszek Giefing, Witold Pazdrowski, Tomasz Jelonek, Arkadiusz Tomczak, Grzegorz Kupczyk
Department of Forest Utilization, University of Life Sciences in Poznań, Poland

ABSTRACT

The investigations aimed at the determination of the share of juvenile, maturing (transition) and mature wood in stems of Norway spruce from stands of age class IV. The analyses included spruces of the southern and northern limits, as well as those coming from the so-called spruce-free zone. The shares of individual types of wood in stems varied, depending on the social class of tree position in the stand and on the provenance of analyzed spruces. This trend was manifested more markedly in relation to juvenile wood than in the other types of wood.

Key words: Norway spruce, cyclical heterogeneity, juvenile wood, maturing wood, mature wood, pure density.

INTRODUCTION

Wood tissue formed in leaved stems or in sections located close to leaved branches has a different structure than wood formed in parts distant from assimilatory organs [6,7,8,16,19]. An example of wood formed under a strong influence of assimilatory organs (the crown) at a high availability of growth hormones may be the core wood zone (juvenile wood), formed at an early phase in the life of trees or growing in the top zone of the stem within the crown [13,18,21].

Wood in that zone is characterized by a low share of thick-walled elements (late wood), low density, a lower cellulose content, a large angle of cellulose fibrillar systems in relation to cell axes, shorter fibrous elements, a higher coefficient of shrinkage and distinctly poorer stability [7,8,11,21]. Juvenile wood is found in all trees and its structure and properties differ from those of mature wood tissue of the same tree. The above mentioned variation results in an undesirable heterogeneity of functional properties of wood within a stem [1,2,3,4,9,12,14,15,17].

Zobel and Talbert [22] were of the opinion that variation of wood properties observed in coniferous species is primarily caused by the presence of juvenile wood and its ratio in relation to mature wood in a tree, especially in the commercial bole.

The above mentioned traits have a decisive effect on physico-mechanical properties of wood, determining its possible utilization. Knowledge on properties of juvenile wood and the determination of its share in tree stems will facilitate optimization of its conversion and utilization of timber in the production process in wood industry.

The aim of this study was to determine the share of juvenile, transition (maturing) and mature wood in stem profiles of Norway spruce from different parts of Poland depending on the social class of tree position in the stand.

MATERIAL AND METHODS

Experimental material was collected from the area of the following forest inspectorates: Szklarska Poręba – Regional State Forests Directorate in Wrocław (the southern range of spruce), Wisła – Regional State Forests Directorate in Katowice (the southern range of spruce, Spychowo – Regional State Forests Directorate in Olsztyn (the northern range of spruce) and Mieszkowice – Regional state Forests Directorate in Szczecin (an area outside the natural range of spruce).

Sample plots were established in spruce stands of age class IV in stands of site class I or I/5 with stocking of 0.8 and 0.9. They occupied typical sites for spruce: in the mountains in mixed mountain forest sites (LMG), while in the lowlands mixed broadleaved forest sites in Mieszkowiceh (LM) and fresh mixed broadleaved forest (LMœw) in Spychowo. In the Wisła Forest Inspectorate analyses were conducted on stands from natural regeneration with overplantings. The other stands originated from plantings.

Analyses were conducted on spruces of the southern and northern ranges as well as those coming from the so-called spruce-free zone. In the established mean sample plots (1ha) measured values included breast height diameters, tree heights and the location of the first live branch (the starting point of the tree crown). After diameter and height characteristics of the stand were recorded, sizes of model (mean) stems were calculated using the Ulrich II dendrometric system [5]. After they had been selected the northern exposure was marked on every mean tree. These trees differed in terms of their social class of tree position in the stand. In age class IV the biggest trees occupied the best social class of tree position, corresponding to Kraft’s class I, while smaller trees represented Kraft’s class III. A total of 12 trees were included in the study, three in each mean plot.

After trees were felled their height and the width of live crown were measured. Material for further analyses were collected in the form of the butt end disc and further discs cut at a distance of 1.0 m and next at every 2.0 m up to the top. Discs were used to measure the width of the early and late wood zones in successive annual rings. Measurements were taken using an electronic increment meter coupled with a computer. The calculated ratio of the width of the late to early wood zones was the basis for the isolation of juvenile, transition and mature wood zones. Recorded data made it possible to determine the shares of individual types of wood in stems of model (mean) trees. Boundaries of juvenile, transition and mature wood zones were identified on the individual basis for each tree [20]. The ratio of early to late wood changed significantly, clearly differentiating individual wood zones.

RESULTS

Three wood zones, i.e. juvenile, maturing (transition) and mature wood, were found in the stems of all analyzed model trees from individual mean sample plots (Figs. 1-4).

The shares and distribution of the above mentioned wood types were irregular (especially in the Wisła Forest Inspectorate, Fig. 1) and characterized by high variation in axial sections of the stem. Only in trees occupying in the analyzed stand the worst social position (Kraft’s class III) the distribution and shares of individual wood types at individual heights showed regularity typical of the axial variation. In other trees the shares and distribution of individual wood types were irregular and unrelated with tree height (Fig. 1). These findings were most probably the result of changes in growth conditions of analyzed spruces in individual development stages of the stand and first of all were the effect of changing parameters of the live crown and dynamics of branch dying. It needs to be remembered that trees throughout their life, starting from the young growth stage to the physiologically mature specimens, may change their social class of tree position in the stand. A change in the social position of trees in the stand may be modified by many factors, including the regeneration method (natural or by planting), silvicultural and management measures (thinnings), diseases, etc.

Fig. 1. The distribution of juvenile, transition and mature wood in cross stem sections of spruces in the Wisła Forest Inspectorate

Fig. 2. The distribution of juvenile, transition and mature wood in stem sections of spruces in the Szklarska Poręba Forest Inspectorate

Fig. 3. The distribution of juvenile, transition and mature wood in the stem profiles of spruces with different classes of tree position in the stand (the Mieszkowice Forest Inspectorate)

Fig. 4. The distribution of juvenile, transition and mature wood in the stem profile of spruces from different classes of tree position in the stand (the Spychowo Forest Inspectorate)

Special emphasis should be placed on the transition and mature wood zones in social class I. In this respect irregular distribution of the juvenile wood zone is a striking feature. It most probably is the effect of radical changes in the development conditions of analyzed trees as a result of performed management interventions. These measures could have significantly improved access to light of individual trees, especially in stands from natural regeneration, usually growing at dense canopy. In the other mean sample plots the share of juvenile wood was distributed evenly over the entire axial section of trees.

Usually a smaller range of mature wood and a slightly bigger range of maturing wood is observed (Figs. 2, 3, 4). In the Wisła Forest Inspectorate the axial distribution of individual wood zones was unusual. The range of maturing and mature wood ended at a height of approx. 30 m and marked clearly the beginning of the light part of the crown, within which only juvenile wood is formed (Fig. 1). It needs to be stressed that in spruces juvenile wood is not formed in the entire crown zone, but rather in its light part, characterized by an advantageous assimilate balance. In the shade crown, where assimilate balance may even be negative, maturing or mature wood is formed.

In the Szklarska Poręba Forest Inspectorate (Fig. 2) vertical ranges of individual wood types were markedly varied. The share of juvenile wood in stems is closely correlated with crown size, first of all with the size of its light part. Crown size is usually the result of tree height, which determines its social class of tree position in the stand. Thus, it seems natural that the highest share of this zone was found in tress of Kraft’s class I. In contrast, the low share of transition and mature wood in the axial section of the tree of Kraft’s class III was surprising (Fig. 1). It may be explained only by the tree losing a good social position in the stand during the last stage of its development.

During the analysis of the vertical distribution of individual wood types the range of maturing wood may be considered highly typical. In contrast, the very small range of mature wood in the tree from the best social class, amounting to only 17 m, was surprising. Most probably the crown of this tree was well-lighted for a long time. In radial stem sections of the tree from Kraft’s class I in the lower parts of the stem, despite the considerable share of juvenile and transition wood, mature wood was found in biggest quantity, which was determined by the considerable dimensions of the tree. At the same time it needs to be mentioned that the 17-meter range of mature wood in the tree with the best social class of tree position in the stand, in comparison to tree height of 29 m, was slight and amounted only to 58.6% of its height (Fig. 2), whereas in the tree from Kraft’s class II the range of mature wood in the axial stem section was as much as 92%. A similarly high share of mature wood in the axial stem section was recorded for the tree with the worst class of tree position in the stand. This confirms the opinion that in spruce the type of formed wood is determined by the light part of the crown. The distribution of individual wood types at the axial stem section was undoubtedly determined by the more limited access to light of trees from the inferior social positions in the stand.

It needs to be stated that in trees from inferior social classes of tree position the share of juvenile wood in cross stem sections was relatively high, which resulted mainly from the low proportion of mature and transition wood formed in radial sections.

In the longitudinal stem sections of trees in the Mieszkowice Forest Inspectorate (Fig. 3) zones of juvenile, transition and mature wood were well-marked. The effect of social class of tree position in the stand on the proportion of juvenile wood may be easily observed at the longitudinal stem sections.

In trees from inferior social classes of tree position tree height and at the same time the vertical range of individual wood types were observed to decrease. In the co-dominant tree it was found at a height of 18 and 21 m, while in the tree from the worst social position it was at a height of 17 m. In the latter case the range of maturing and mature wood was identical.

Moreover, the axial share of individual wood types at the axial stem sections needs to be focused on. In trees with the best social class of tree position juvenile wood was deposited at a width of approx. 70 mm, with the range of juvenile wood decreasing gradually at a height over 15 m, only to increase its range at a height of 23 m.

In the Mieszkowice Forest Inspectorate trees in inferior social positions were characterized by a lower share of juvenile wood, which confirms opinions quoted on this subject. In trees with average parameters (Kraft’s class II) almost over the entire axial section of the stem it was approx. 50 mm, while in the tree occupying the worst social position it was only approx. 30 mm, whereas in the dominant trees, as it was already mentioned, its range was as much as 70 mm.

In the Spychowo Forest Inspectorate (Fig. 4), similarly as in the previously analyzed mean sample plots, the effect of the social class of tree position in the stand on the amount of juvenile wood in the longitudinal stem section was evident. In the thickest tree juvenile wood was deposited at a width of approx. 60 mm, with the range of juvenile wood decreasing gradually in the higher sections of the tree, only to increase again at a height of 4-6 m below the top.

Table 1. The ratio of vertical range of transition and mature wood to tree height

Forest Inspectorate Spychowo	Kraft’s class I	Kraft’s class II	Kraft’s class III
transition	0.83	0.84	0.95
mature	0.81	0.76	0.81
Forest Inspectorate Mieszkowice	Kraft’s class I	Kraft’s class II	Kraft’s class III
transition	0.90	0.78	0.74
mature	0.61	0.70	0.74
Forest Inspectorate Wisła	Kraft’s class I	Kraft’s class II	Kraft’s class III
transition	0.84	0.91	0.93
mature	0.77	0.85	0.88
Forest Inspectorate Szklarska Poręba	Kraft’s class I	Kraft’s class II	Kraft’s class III
transition	0.86	0.95	0.91
mature	0.58	0.93	0.91

In a tree with average parameters an especially large share of juvenile wood may be observed. The share of juvenile wood in tree stems is connected with crown size, especially with the size of the light crown, which range depends on tree height and the occupied social class of tree position in the stand. Thus, a natural consequence of the above statement is the biggest share and range of juvenile wood in trees of Kraft’s class I.

The ratio of the axial range of transition and mature wood to the total tree height is also of interest (Table 1). Obviously, juvenile wood was not taken into account, since it is located throughout the entire length of the axial stem section. Thus, its range is equivalent to tree height. Most frequently the share of transition wood was also considerable. Usually it was more than 0.80 and in many cases it exceeded 0.90. The share of mature wood was more varied and ranged from 0.58 in Kraft’s class I in the Szklarska Poręba Forest Inspectorate to 0.91 in Kraft’s class III in the same inspectorate.

DISCUSSION

In all analyzed trees the share of juvenile wood in the axial section increased starting from the butt end to the top and reached the maximum within the crown. Thus, juvenile wood was formed in biologically youngest parts of the tree profile.

At the initial stage of wood deposition in tree stems juvenile wood is formed. It is most frequently deposited during the 10 – 20 years of a tree’s life under the strong influence of the photosynthesizing organ (the crown) [7,8,13]. Results recorded in this paper show that in spruce this process may last longer, up to several decades (Figs. 1, 2, 3 and 4). Wood tissue formed at a later time is defined as mature wood. The above mentioned zones are found in varied proportions in tree stems. This is determined by several factors, first of all site conditions and performed silvicultural measures [10]. A similar opinion was also presented in previously mentioned studies [14,15]. Giefing et al. [2,3] pointed to the special role of the social class of tree position in the stand, occupied by a given tree in the course of the stages of deposition of individual wood types. Trees from the best social positions were generally characterized by a larger share of juvenile wood. Access to light of tree crowns was essential in this respect. This opinion was justified by findings recorded in the study and first of all by the different phase structure in spruces from natural regeneration in comparison to spruces from plantings.

Moreover, a different effect of the light and shade parts of the crown in spruces on the deposition of different wood types was also observed. It is a phenomenon differentiating the course of this process in spruce and pine. In pine, being a light demanding, fast self-pruning species, which photosynthesizing organ does not have sufficient access to light, juvenile wood is deposited over the entire stem part with the live crown [13,18,20]. In spruce, which is a shade-tolerant species, retaining needled branches for a long time, we may distinguish the light and shade parts of the crown. Juvenile wood is formed in the light part, while in the shade crown transition or even mature wood is already deposited.

Thorough knowledge on quantitative traits of juvenile, transition and mature wood in tree stems may be crucial in the optimization of conversion and utilization of timber obtained from spruce stands.

CONCLUSIONS

1. Spruce wood is characterized by radial and vertical variation of formed wood tissue, defined as cyclical heterogeneity of wood structure.

2. Spruces from stands of age class IV had three types of wood in their stems: juvenile, maturing (transition) and mature wood. The shares of individual wood types varied, with taller trees and those with larger dimensions having considerably more juvenile wood than it was the case with lower and thinner spruces.

3. The general characteristic of vertical cyclicity of wood structure in spruces is the formation of only juvenile wood in the parts of the tree located highest (i.e. biologically youngest), juvenile wood being surrounded with a coat of maturing (transition) wood at the crown base and wood typical of all the three development phases found in the axial section below the crown.

4. In vertical cyclicity of spruce wood structure the highest share of juvenile wood was usually observed in trees from the best social classes of tree position in the stand and the highest share of mature wood - in co-dominant trees (from medium-quality social positions).

5. In biologically youngest parts of trees juvenile wood was formed irrespective of the age of the tree.

6. Social position of trees in the stand and growth conditions, resulting from the adopted method of stand regeneration, to a considerable degree determined the share and distribution of juvenile, transition and mature wood in tree stems.

7. In spruces juvenile wood is formed in the light part of the crown. In the shade crown maturing and mature wood are deposited.

REFERENCES

1. Bendsten B.A., 1978. Properties of wood from improved and intensively managed trees. Forest Prod. J. 28, 10-61.

2. Giefing D.F., Pazdrowski W., Spława-Neyman S., Jelonek T., Tomczak A., Szczepaniak J., Kupczyk G. 2005a. Niejednorodnosc cykliczna drewna swierka pospolitego Picea abies (L.) Karst. z drzewostanów przedrębnych a jego własciwosci techniczne [Wood cyclic heterogeneity of Norway spruce (Picea abies (L.) Karst.) derived from maturing stands and its technical properties]. Projekt KBN 3P06L00623 [in Polish].

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4. Gorman T.M. 1985. Juvenile wood as a cause of seasonal arching in trusses. Forest Prod. J. 35, 11/25-35.

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7. Hejnowicz Z. 1973. Anatomia rozwojowa drzew [Developmental anatomy of trees], PWRiL, Warszawa [in Polish].

8. Hejnowicz Z. 2002. Anatomia i histogeneza roslin naczyniowych [Anatomy and histogenesis of vascular plants]. PWN, Warszawa [in Polish].

9. Helińska-Raczkowska L. 1993. Zdolnosc do utrzymywania gwozdzi przez młodociane drewno sosny zwyczajnej. [Withdrawal resistance of nails from juvenile wood of Scots pine] Sylwan 7, 9-31 [in Polish].

10. Jakubowski M. 2004. Udział bielu, twardzieli, drewna młodocianego i dojrzałego w strzałach sosen zwyczajnych (Pinus sylvestris L.) wyrosłych w różnych warunkach siedliskowych [The share of sapwood, heartwood, juvenile and mature wood in pine stems (Pinus sylvestris L.) in relation to site conditions]. Sylwan 8, 16-24 [in Polish].

11. Kretschmann D. E. 1998. Properties of juvenile wood. Techline: Properties and Use of Wood, Composites, and Fiber Products, Forest Service, Issued 9.

12. Lewark S. 1986. Anatomical and physical differences between juvenile and adult wood. Proc. 18th IUFRO World Congress. Div.5. Ljubljana 7-21 Sept. 272.

13. Niedzielska B., Wšsik R. 2000. Badania zmiennosci cech drewna jako podstawa do racjonalnego kształtowania jego jakosci. [Variability examination of wood features as a base of its quality formation] Materiały III Konf. Lesnej IBL, Warszawa, 259-267 [in Polish].

14. Pazdrowski W. 2004. The proportion and some selected physical and mechanical properties of juvenile, maturing and adult wood of Black pine and Scots pine. EJPAU 7(1) #03, http://www.ejpau.media.pl/volume7/issue1/forestry/art-03.html.

15. Pazdrowski W. Spława-Neyman S. 2003. Stage growth of trees and its effect on selected properties Norway spruce wood (Picea abies (L.) Karst.). EJPAU 6(2) #02, http://www.ejpau.media.pl/volume6/issue2/forestry/art-02.html.

16. Rendle B. J. 1960. Juvenile and adult wood. Journal of the Institute of Wood Science 5, 58-61.

17. Senft J.F. 1986. Practical significance of juvenile wood for the user. Proc. 18 th IUFRO World Congress. Div.5. Ljubljana 7-21 Sept. 261.

18. Spława-Neyman S., Szczepaniak J. 2000. Niejednorodnosc cykliczna budowy drewna iglastego [Cyclical heterogeneity of coniferous timber structure]. Materiały XIII Konferencji Naukowej Wydziału Technologii Drewna SGGW, 21-24, Warszawa [in Polish].

19. Thörnqvist T. 1993, Juvenile wood in coniferous trees. Document D13, Uppsala.

20. Tomczak A., Pazdrowski W., Jelonek T., Stypuła I. 2007. Vertical variability of selected macrostructural properties of juvenile wood organisation in trunks of Scots pine (Pinus sylvestris L.) trees. Acta Societatis Botanicorum Poloniae 76, 1, 27-33.

21. Zobel B. J., Sprague J. R. 1998, Juvenile wood in forest trees. Springer – Verlag, Berlin Heidelberg New York.

22. Zobel B., Talbert J. 1984. Applied forest tree improvement. John Viley & Sons, New York.

 

Accepted for print: 29.01.2008

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Dieter Franciszek Giefing
Department of Forest Utilization,
University of Life Sciences in Poznań, Poland
Wojska Polskiego 71A, 60-625 Poznań, Poland
Phone: +48 61 848 77 54
email: giefing@au.poznan.pl

Witold Pazdrowski
Department of Forest Utilization,
University of Life Sciences in Poznań, Poland
Wojska Polskiego 71 A, 60-625 Poznań, Poland
Phone: (+48 61) 8487757
email: kul@au.poznan.pl

Tomasz Jelonek
Department of Forest Utilization,
University of Life Sciences in Poznań, Poland
Wojska Polskiego 71 A, 60-625 Poznań, Poland
Phone: (+48 61) 8487754
email: tjelonek@au.poznan.pl

Arkadiusz Tomczak
Department of Forest Utilization,
University of Life Sciences in Poznań, Poland
Wojska Polskiego 71 A, 60-625 Poznań, Poland
Phone: (+48 61) 8487754
email: atomczak@au.poznan.pl

Grzegorz Kupczyk
Department of Forest Utilization,
University of Life Sciences in Poznań, Poland
Wojska Polskiego 71A, 60-625 Poznan. Poland

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