The effects of Forest Harvesting Techniques on Optimum Bucking Application of Oriental Spruce (Picea orientalis) Stands in Turkey

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1 The effects of Forest Harvesting Techniques Seite Jahrgang (2009), Heft 1, S The effects of Forest Harvesting Techniques on Optimum Bucking Application of Oriental Spruce (Picea orientalis) Stands in Turkey Einfluss der Holzerntetechnik auf eine Optimierung der Wertholzausbeute von Orient-Fichtenwälder (Picea orientalis) in der Türkei Key Words: Optimum bucking, Harvesting techniques, Log production, Oriental spruce Schlagwort: Optimierungsverfahren, Erntetechnik, Wertschöpfung, Orient-Fichte Summary One of the most important industrial wood-based products are the logs which are produced by bucking the trees into shorter lengths. Optimum bucking of the trees is a key factor to increase productivity of log production, depending on log grade, log sizes, and unit prices. Previous optimum bucking studies in Turkey indicated that optimum bucking methods tend to produce longer logs to maximize total tree values. However, groundbased manual skidding, the most common traditional harvesting technique in Turkey, can not handle large size logs, which may diminish the potential success of the optimum bucking method. In this study, the effects of forest harvesting techniques on optimum bucking method was investigated du-

2 Seite 26 ring a logging operation in Oriental Spruce (Picea orientalis) stands in the city of Giresun in northeastern Turkey. Two harvesting techniques, including ground-based manual skidding and ground-based mechanized skidding, were evaluated by considering the maximum allowable log lengths (i.e. 4 m and 5 m, respectively). The results indicated that mechanized logging systems will allow an optimization of the log length and this will lead of an increase in the economic value of the harvested timber of approximately 11%. Zusammenfassung Eines der wichtigsten industriellen Holzprodukte ist das Bloch, das durch ablängen der Stämme in kürzere Teile hergestellt wird. Das optimierte Ablängen der Stämme ist ein Schlüsselfaktor, um die Produktivität der Holzausbeute zu steigern. In bisherigen Studien zur Optimierung des Ablängens in der Türkei haben gezeigt, dass die Optimierung dahin tendiert, längere Bloche zu erzeugen, um den Gesamtwert des Baumes zu maximieren.. Allerdings können längere Bloche durch händisches Rücken, wie dies in der Türkei üblich ist, kaum oder nur sehr schwer bewältigt werden. In dieser Studie wurde der Einfluss von Holzerntetechnik auf die Optimierung des Ablängens während eines Erntevorgangs in einem Orient-Fichten Bestand (Picea orientalis) in der Stadt Giresun im Nordosten der Türkei untersucht. Zwei Erntetechniken, händisches und mechanisiertes Rücken wurden unter Berücksichtigung der maximal zulässigen Bloch-Längen (d.h. 4 m bzw. 5 m) ausgewertet. Die Ergebnisse zeigten, dass bei der mechanisierten Rücken, dass die Optimierung auf die maximal zulässige längere Blochlänge ermöglicht, der wirtschaftliche Wert der geernteten Bäume um ca. 11% erhöht werden konnte. Introduction Forest resources have been under great pressure due to intense public demand on direct use values of forests such as wood-based products, nonwood products and recreational uses. Population growth, industrialization and economic development have escalated consumer demands on woodbased products in particular, which also represent the highest proportion in total economic value of forest resources (SERIN et al. 2010). Therefore, wood-based products, as the primary income sources of the forest indus-

3 The effects of Forest Harvesting Techniques Seite 27 tries, should be produced by using appropriate methods and by ensuring sustainable management of forest resources. Besides, even a small amount of loss should not be disregarded in the production of wood-based forest products (UNVER and ACAR 2009a). In the Turkish forest industry, the main wood-based products include logs, wire poles, mine poles, industrial wood, pulp wood and fire wood. The most important wood product is considered to be logs in terms of quantity and economic value. The proportion of log production in the year 2008 was approximately 34.19% and 49.18% of the total quantity and value of wood based products, respectively (YENILMEZ 2010). In the process of log production, trees are first cut, delimbed, topped, and then bucked into the shorter lengths. Bucking the cut trees into logs that maximize the total value of the trees is defined as optimum bucking (SES- SIONS 1988). In Turkey, trees are cut by traditional bucking method depending on the loggers experiences. However, implementing an optimum bucking method has great potential to increase the total economic value of log production in the Turkish forest industry. Previous studies have indicated that optimum bucking methods can increase the economic value up to 12% (AKAY et al. 2009). In implementing optimum bucking methods, computerassisted optimizations techniques are required to search for the optimum solution among a large number of alternative bucking solutions. The most common optimization techniques used in optimum bucking applications include network analysis, linear programming, dynamic programming, and heuristic techniques (LAROZE and GREBER 1997). Optimum bucking studies conducted within Turkish forestry conditions have indicated that the average length of the logs produced by optimum bucking methods are longer than that of those produced by traditional bucking methods (AKAY et al. 2009). Besides, the economic value gain of harvested trees, which are bucked by using optimum bucking methods, tends to increase as the length of the bucked logs increases (YENILMEZ, 2010). However, the length of the bucked logs are generally limited by the low standard of forest roads (i.e. short curve radiuses, narrow line widths, etc.), and traditional forest harvesting techniques of ground-based manual skidding with minimal or no mechanization (UNVER and ACAR 2009b). In this study, the effect of ground-based manual skidding and ground-based mechanized skidding on the optimum bucking method was investigated during a logging operation in Oriental Spruce (Picea orientalis) stands in northeastern Turkey. Two optimum bucking applications were performed, considering two different maximum allowable log lengths representing the harvesting techniques (i.e. 4 m for manual skidding and 5 m for mechanized skidding).

4 Seite 28 Material and Methods Field Study The study area was selected from Oriental Spruce (Picea orientalis) stands located in Esenli Forest Enterprise Chief of Espiye Forest Enterprise Directorate in Giresun Forest Regional Directorate (Figure 1). The average elevation and ground slope were 1,621 m and 64%, respectively. The Oriental Spruces were cut and bucked using a chainsaw depending on traditional bucking methods in June To approximate the normal distribution, optimum bucking methods were applied to 30 randomly selected sample trees. In the field study, necessary optimum bucking data including log diameter, log length, and log grade were recorded for each sample tree log. The tree height and tree diameter at breast height were measured for each sample tree by using chain tape and compass. In addition to this, UTM coordinates were recorded at the stump locations of sample trees by using a hand-held GPS. The logs were then transported to the landing areas using ground-based manual skidding technique. Optimum Bucking Method In this study, a dynamic programming method with a node-labeling technique was used to develop a stem-level optimum bucking algorithm (SES- SIONS et al. 1988a). In this algorithm, possible bucking locations were considered as nodes and each arc between nodes as possible log lengths (Figure 2). The value of the arc represents the value received from the log. The log value was computed by multiplying the log volume by unit log price. The log volume was computed as a function of log length and diameter at the mid-point of the log. The unit log price can be obtained from the most recent local auctions. Then, the optimum path of arcs that yields maximum economic value from the whole tree was determined by the algorithm. Logging cost, transportation cost, and stumpage payments were neglected in the algorithm. In order to effectively implement optimum bucking methods, log grades and log sizes (i.e. diameter and length) should be accurately entered into the algorithm. Additionally, current information about the market prices should be available for each log grade with various length and diameter classes (SESSIONS et al. 1988b). The diameter and length classes used for Oriental Spruce trees in Turkey are indicated in Table 1 (Kalıpsız 1999). The

5 The effects of Forest Harvesting Techniques Seite 29 average log price for each log grade is obtained from Espiye Forest Enterprise Directorate (Table 2). Table 1: The length and diameter classes for the logs of coniferous trees. Length Classes Length (m) Diameter Classes Middle Diameter (cm) Short (S) Small (SD) Normal (N) Medium (MD) Long (L) Large (LD) Very Long (VL) 8.5 Very Large (VLD) 50 Table 2: Unit prices of the logs with various length and diameter classes. Length and Log Prices (EURO/m 3 ) Diameter Classes I. Grade II. Grade III. Grade S-SD S-MD S-LD S-VLD N-SD N-MD N-LD N-VLD L-SD L-MD L-LD L-VLD To determine feasible alternatives, the optimum bucking algorithm considers various decision variables such as maximum log lengths, minimum log length, and minimum log diameter at the mid-point of a log. In log production practices in Turkish forestry, the minimum log length and minimum log diameter at the mid-point of a log are generally considered as 2 m and 19 cm, respectively. The maximum log length is however limited by local factors such as market demand and the capabilities of harvesting techniques. In this study, two different maximum log lengths were consi-

6 Seite 30 dered to evaluate the effects of two harvesting techniques on two different optimum bucking scenarios, assuming that there is market demand for both log lengths. In the first scenario, the maximum log length of 4 m was used for ground-based manual skidding technique. In the second scenario, the maximum log length of 5 m was used for ground-based mechanized skidding technique, assuming that longer logs can be produced by utilizing mechanized harvesting. Figure 1: Measuring bucked logs for optimum bucking applications (Photo: A.E. Akay). Figure 2: Network representation of a sample tree. Results and Discussion In the first scenario, bucking patterns generated by optimum bucking methods were different from the bucking patterns generated by the traditional bucking method for all of the sample trees except for the 20th sample tree (Table 3). Previous studies reported that the loggers using traditional bucking methods may reach the same bucking pattern of optimum bucking methods for trees with straight stems and few defects (WANG et al. 2004).

7 The effects of Forest Harvesting Techniques Seite 31 In the second scenario, bucking patterns generated by optimum bucking methods were different from the bucking patterns generated by the traditional bucking methods for all of the sample trees. Table 3: The bucking patterns generated by the bucking methods for both scenarios. I. Scenario II. Scenario Tree No Traditional Bucking Optimum Bucking Traditional Bucking Optimum Bucking

8 Seite 32 The results indicated that the average diameter at breast height and average height of the sample trees were cm and m, respectively. The UTM coordinates of the sample trees were recorded into Microsoft Excel and a tree distribution map was generated by using Add XY Data tool of ArcGIS 9.2 software (Figure 3). Figure 3: Forest Enterprise Chiefs (FECs) in Turkey and distribution of the sample trees in Esenli FEC. The average log lengths of the sample trees bucked by optimum bucking methods were computed as 3.29 m and 3.85 m in the first and second scenario, respectively. This indicated that increasing the maximum log length from 4 m to 5 m resulted in an 18% increase in the average length of logs produced by optimum bucking method. The average log lengths of the sample trees bucked by optimum bucking methods were regrouped into four classes (short < 3.0 m, normal = m, long = m, very long > 4.0 m) to understand the distribution of the sample trees according to the average log lengths. In the first scenario, the distribution of the sample trees according to average length of the logs produced by optimum bucking methods is shown in Figure 4. This figure

9 The effects of Forest Harvesting Techniques Seite 33 indicated that 70% of the sample trees were in the normal log length class, while 20% and 10% of the trees fell into long and short log length classes, respectively. Figure 4 also shows the distribution of the sample trees according to the average length of the logs produced by optimum bucking method in the second scenario. It was found that 73% of the sample trees were in the long log length class, while in the second scenario, 17% and 10% of the trees fell into the normal and very long log length classes, respectively. Figure 4: The distribution of the sample trees according to log length for the first (left) and the second scenario (right). In Table 4, the economic values of sample trees produced by both bucking methods and the average value gain of using optimum bucking methods were listed for two scenarios. In the first scenario, the average economic value of sample trees produced by optimum bucking methods was Euro, while it was found that the average economic value of sample trees produced by traditional bucking methods was Euro. Thus, using optimum bucking methods increased the potential average value of the sample trees by 8.55%. In a similar study, where optimum bucking methods with maximum log length of 4 m was applied on sample Brutian Pine trees, it was reported that the average economic value gain of using optimum bucking method was about 9.31% (YENILMEZ 2010). In the second scenario, the average economic value of sample trees produced by optimum bucking methods was Euro, while it was found that the average economic value of sample trees produced by traditional bucking methods was Euro. Thus, using optimum bucking method increased the potential average value of the sample trees by approximately 11.26%. In a similar study, where optimum bucking methods with maximum log length of 5 m was applied on sample Caucasian Fir trees, it was reported that the average economic value gain of using optimum bucking methods was about 12% (AKAY et al. 2010).

10 Seite 34 Table 4: The economic values of sample trees produced by bucking methods and average value gain of using optimum bucking methods for two scenarios. Tree No Economic Values (Euro) Traditional Bucking I. Scenario II. Scenario Optimum Bucking Value Gain (%) Economic Values (Euro) Traditional Bucking Optimum Bucking Value Gain (%)

11 The effects of Forest Harvesting Techniques Seite 35 The results indicated that implementing computer-assisted optimum bucking methods as a decision support tool considerably increased the economical value of the harvested trees. Besides, increasing the maximum log length from 4 m to 5 m by utilizing mechanized skidding technique increased the potential value gain of optimum bucking methods from 8.55% to 11.26%. The optimum bucking and harvesting techniques should not be considered as completely separate operations. The findings from this study indicated that the usage of mechanization in harvesting operations should be increased in the area to improve the performance of optimum bucking methods. Acknowledgement This study was funded by The Scientific and Technological Research Council of Turkey (TUBITAK) with the project number 108O125. References AKAY A.E., SERIN H., Pak M. and YENILMEZ N Using Computer-Assisted Optimum Bucking Method in Producing Log. III. Blacksea Forestry Congress. Artvin. Turkey. 8 p. AKAY A.E., SERIN H., PAK M. and YENILMEZ N Applying Optimum Bucking Method in Log Production. Bartın University, Faculty of Forestry Journal. (2): KALIPSIZ A Dendrometry. Istanbul University, Faculty of Forestry. Publication No: 3194/354. Istanbul. Turkey. 407 p. LAROZE A.J. and GREBER B.J Using Tabu Search to Generate Stand-Level, Rule-Based Bucking Patterns. Forest Science. 43(2), SERIN H., AKAY A.E. and PAK M Estimating the Effects of Optimum Bucking on the Economic Value of Brutian Pine (Pinus Brutia) Logs Extracted in Mediterranean Region of Turkey, African Journal of Agricultural Research, 5(5): SESSIONS J Making Better Tree Bucking Decisions in the Woods: an Introduction to Optimal Bucking. Journal of Forestry. 86(10), SESSIONS J., LAYTON R. and GUANGDA L. 1988a. Improving tree bucking decisions: A net-work approach. The Compiler. 6(1), 5-9. SESSIONS J., GARLAND J. and OLSEN E. 1988b. BUCK: A computer program for optimal tree bucking. The Compiler. 6(3),

12 Seite 36 UNVER S. and ACAR H.H. 2009a. A Damage Prediction Model for Quantity Loss of Skidded Spruce Logs during Ground Based Skidding in North Eastern Turkey. Croatian Journal of Forest Engineering. 30(1), UNVER, S. and ACAR, H.H. 2009b.Evaluation of Residual Tree Damage in Sloping Areas Due to Harvesting Operations by Manually. Austrian Journal of Forest Science. 126(3), WANG J., LEDOUX C.B. and MCNEEL J Optimal Tree-Stem Bucking of Northeastern Species of China. Forest Products Journal. 54(2), YENILMEZ N Applying a Single Tree Level Optimum Bucking Method during Cut-to-length Logging. M.Sc. Thesis. KSU, Faculty of Forestry, Kahramanmaras. Turkey. 216 p. Author: : Faculty of Forestry, Kahramanmaras Sutcu Imam University, Kahramanmaras, Turkey. Tel: /453 Fax: akay@ksu.edu.tr