Stand Damage of a Selection Cutting System in an Uneven Aged Mixed Forest of Cimendagi in Kahramanmarz-Turkey

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INTRODUCTION
In managing forest resources, one of the most desirable
stand types in terms of sustaining the biodiversity is uneven-
aged mixed forests where many tree and shrub species can
live together with harmony. The uneven-aged mixed forests
are highly resistant against biotic and abiotic agents and they
provide rich gene combinations and genetic variations [14,
8, 18]. Besides, they improve the visual quality and aesthetic
value of the forest stand.
In uneven-aged mixed forest, forest managers mostly apply
selection system which ensures and sustains uneven-aged
forests, consisting of single trees or group of trees with various
age, height, and diameter classes [7]. In selection system, the
stand is divided into cutting blocks and each block is periodically
(e.g. period of 10 years in Turkey) treated by implementing
either single tree selection cutting or group selection cutting
method [7]. The single tree selection cutting favors growth
of shade tolerant species (e.g. fir, beech, spruce) while group
selection favors the regeneration of light demanding species
(e.g. pines). In mixed forest containing both shade tolerant
and light demanding species, group selection cutting should
be applied. After implementing selection cutting method, the
natural regeneration can occur in the open areas where trees
are extracted.
In applying selection cutting method, inadequate and poor
logging operations (i.e. felling and skidding) may cause serious
damages on residual stands due to existence of various tree
species with different age classes. In uneven-aged forests, the
amount of residual stand damages after logging is more than
within even-aged forests [9]. The injured residual trees loss
considerable amount of timber volume and economical value,
and they become more vulnerable to insect and fungus attacks.
Furthermore, damaging young trees results in a long term impact
on regeneration process of uneven-aged mixed forests. Besides,
uneven-aged forests require frequent silvicultural treatments that
of even-aged forests [22]. Therefore, when executing a logging
activity as a tool of implementing silvicultural treatments [19]
in uneven-aged mixed forests, special felling and skidding
operations should be performed to minimize residual stand
damage and to secure natural regeneration process [21]. It
should be noted that applying special techniques in selection
cutting to reduce stand damage may increase the cost of logging
activities [15].
To reduce stand damage in uneven-aged mixed forests
during selection cutting operations, felling directions should be
predetermined, road networks should be well planned, loggers
and operators should be experienced and adequately trained,
skidding distance should be kept shorter, and natural logging
residuals (i.e. slash materials) should be bunched in the woods
[5, 23, 13, 10, 21, 6, 2, 12, 20]. To reduce stand damage, the
type of selection cutting method (i.e. single tree selection
cutting or group selection cutting) should be also determined
carefully by considering local stand characteristics. According
to Stokes et al. [25], number of injured trees in using group
selection method (e.g. average 37.5 tree/ha) is more than that of
using single tree selection method (e.g. average 29.8 tree/ha).
In mountainous terrains, selection cutting is highly
preferable to reduce damages on residual trees as well as end-
products. In some parts of the world, chute system is widely
used to extract timber in steep terrains. For example, wooden
chute system has been used for over 200 years in China. In steep
terrain, the chutes should be located diagonal to the contours
while they should be perpendicular in gentle terrains [1]. The
average yarding distance in chute system varies from 200-1000
m in the ground slope of 45-60%.
In order to determine the most appropriate logging activity
with minimum stand damage, stages of logging operation (i.e.
felling and skidding) should be well analyzed in terms of their
Stand Damage of a Selection Cutting System in an Uneven Aged Mixed Forest
of Çimendaği in Kahramanmaras-Turkey
Mustafa YILMAZ, Abdullah E. AKAY*
KSU, Faculty of Forestry, Forest Engineering Department, 46060 Kahramanmaras, Turkey
* Corresponding Author Received: September 12, 2007
e-mail: akay@ksu.edu.tr Accepted: November 30, 2007
Abstract
In the uneven-aged mixed forests, logging operation is generally performed by using selection cutting method. However, log-
ging activities result in serious residual stand damages during felling and skidding operations in these stands. Therefore, the effects
of main factors on stand damage should be well understood by the logging managers to plan proper logging operations with mini-
mum damage. In this study, the residual stand damages from a logging operation was studied in an uneven-aged mixed forest to
examine the main factors (i.e. logging stages, tree species, and location, size, and type) affecting stand damages. Then, some of the
suggestions and practices that can be implemented during logging operations to reduce stand damage were presented.
Keywords: Residual damage, mixed stands, logging, felling, skidding,
International Journal of Natural and Engineering Sciences 2 (1): 77-82, 2008
ISSN: 1307-1149, www.nobelonline.net

M. Yilmaz and A. E. Akay / IJNES, 2 (1): 77-82, 2008
78
potential for causing residual stand damage [11]. In this study,
a logging operation conducted in an uneven-aged mixed forest
was studied to examine the stand damages by considering
variable factors including logging stages, tree species, and
location, size, and type of damages.
MATERIAL AND METHODS
Study Area and Stand Characteristics
Study area of 50 ha is located in Çimendağı forest which is
in the boundaries of Hartlap Forest Enterprise Chief in Regional
Forest Directorate of Kahramanmaraş (Figure 1). In the study
area, average elevation and ground slope are 1450 m and 40%,
respectively. The study area consists of an uneven-aged mixed
forest where fir and pine (Pinus nigra) are dominant trees with
scattered cedar trees and very rare junipers and poplar trees.
The average site index in the study area is determined as the
medium site class.
In the study area, the tree diameter classes in the study
area showed an irregular distribution. The number of mature
trees with large diameter classes was more than the optimum
numbers. The forest was multistoried with very dense overstory
and relatively rare understory. However, the forest tends to
return into a single-storied stand due to about 100% crown
closure, which leads to scarcity of sufficient gaps to receive
light for natural regeneration of light-demanding trees including
pine and cedar. The litter layer under the stands dominated by
pine was measured as 5-10 cm while it was measured as 1-2 cm
under the stands of fir trees. Besides, the litters under the pine
were drier and more loosely.
Figure 1. Geographical location of the study area in
Turkey
Logging Operation
In order to ensure sustainability of uneven-aged mixed
forest, selection system has been applied by performing single
tree selection cutting operations within 10 years intervals.
These selection cutting operations include several silvicultural
treatments such as thinning, intermediate cutting, harvesting,
and natural regeneration cutting. In the logging operation, trees
were first fallen by using chainsaw and then transported to the
landing areas by using animal (mule), manpower, and tractor.
Approximately 10% of the timber (49 trees) was extracted
during the operation. The total timber production was about 464
m3 in which two third of the yield was from fir and one third
was from pine.
Table 1. The summary of stand damages based on variable factors including logging stages, tree species, and location, size, and
type of damages.
Sample
Plots
Slope
(%)
Residual
Trees
Extracted
Trees
Trees Species
Damages
Total
Location Type Logging Stage
Fir Pine Cedar <0.30
m
0.30-1.3
m
>1.3
mBark Wood Top Felling Skidding
1 50 33 4 9 0 0 6 4 4 8 5 1 7 7 14
2 35 45 7 4 0 0 4 1 0 2 3 0 1 4 5
3 40 46 3 1 0 1 2 0 0 2 0 0 0 2 2
4 35 41 5 0 1 0 0 1 0 1 0 0 1 0 1
5 40 22 4 3 3 0 6 0 1 3 4 0 2 5 7
6 35 37 3 7 0 0 4 3 0 4 3 0 2 5 7
7 45 36 4 7 0 1 8 4 0 10 2 0 1 11 12
8 30 45 4 0 0 0 0 0 0 0 0 0 0 0 0
9 45 22 4 0 0 0 0 0 0 0 0 0 0 0 0
10 35 26 3 3 0 0 3 1 0 0 4 0 1 3 4
11 55 26 5 3 0 0 1 2 0 1 2 0 1 2 3
12 50 23 3 0 2 0 1 1 0 1 1 0 1 1 2
TOTAL 402 49 37 6 2 35 17 5 32 24 1 17 40 57

M. Yilmaz and A. E. Akay / IJNES, 2 (1): 77-82, 2008 79
Measuring Residual Stand Damage
To analyze stand damages after logging operations, 12
round-shaped sample plots with 400 m2 area were randomly
selected from the study area. Total of 402 residual trees with
breast height diameter of 8 cm or great were considered in data
collection. The number of fir, pine, cedar, and other tress were
198 (49%), 163 (41%), 31 (8%), and 10 (2%), respectively.
The stand damages on trees were examined by considering
variable factors including logging stages (felling or skidding),
tree species (fir, pine, and cedar), and location (stump level:
0-0.3 m, stem: 0.3-1.3 m, upper-stem: 1.3 m and higher), size
(width, lenght, and area), and type of damages (bark, wood, and
top injuries).
RESULTS AND DISCUSSION
Logging Stages
The results indicated that 57 stand damages were counted
on 45 injured residual trees due to the logging operation in the
sample plots (Table 1). The number of stand damages occurred
during the felling and skidding operations were 17 and 40,
respectively (Figure 2).
Figure 2. The view of stand damages due to felling (left)
and skidding (right) operations.
Therefore, one felling injury was occurred for felling of 3
trees (49/17). To minimize felling injuries, directional felling
must be applied considering skidding trails [2]. Besides,
extracted trees should be pruned before felling where it is
necessary [24].
In the study area, three sample plots were located over the
main skidding trails. The number of skidding injuries in those
specific plots was significantly greater than injuries in the other
plots (Figure 3). There were 33 residual stand damages were
detected over the skidding trails. Therefore, the average number
of stand damages occurred in the plots located over the skidding
trails was about 11 (33/3), while the number of damages in the
other plots was about 3 (24/9). To reduce skidding damages,
skidding trails must be predetermined by considering ground
slope, terrain conditions, vegetation density, and harvesting
intensity [5]. Besides, straight skid trails should be designed to
prevent damages on the trees next to the skid trails [16].
Tree Species
The results indicated that the number of injured fir, pine,
and cedar trees were 37, 6, and 2, respectively (Table 1). The
percentages of injured trees were 19% (37/198), 4% (6/163),
and 7% (2/31) for fir, pine, and cedar trees, respectively. The
fir trees received the highest number of damages because
their bark thicknesses are relatively thinner than that of pine
and cedar trees. Besides, almost all of the felling injuries were
detected on firs and cedars since they have dense brunches on
lower stem, comparing with pines which have brunches only on
upper stem due to natural pruning.
Figure 3. Damaged trees over the skidding trail.
The pine trees were injured during the skidding operation
due to impacts of moving logs on butt section and lower section
of the stems. In general, skidding injuries could not penetrate
deep into the wood and cambium due to thick barks of pines.
However, when the logs roll down or move uncontrollably on dry
and loosely litters under the pine dominated stands, they hit the
stems in very high speed and caused injuries on barks and wood.
Considering that four out of six injuries on the pine were on the
wood, one can say that loggers lost control of the logs and they
hit the trees with very high speed. To reduce skidding damages,
loggers should be experienced and well trained for effective and
preservative skidding operations in uneven-aged mixed forest.
Damage Location
The results indicated that the percentages of damages on
stump level, stem level, and upper-level are 61% (35 injuries),
30% (17 injuries), and 9% (5 injuries), respectively (Figure 4).
All of the damages on stump level were caused by skidding
operation. However, on the stem level, 5 out of 17 damages
were occurred due to skidding operation, while felling
operation caused 12 injuries. The damages on upper stem level
were caused by felling operation. When skidding damages
occur on stump level, biotic agents such as fungus and insects
easily attack wood through injuries, especially which close to
the ground [4]. Therefore, injured trees infected by fungus and
insects become subject to considerable amount of value loss in
long run (Figure 5).
Han and Kellogg [16] suggested that artificial tree protection
rigging such as rub pads should be used to prevent damage on
stump and stems. Besides, small size slash material can be
located around the lower tree parts to provide a protection layer.
Stumps height should be low since high stumps on skid trials
can force skidder to move around the stump, which leads to
damages on the trees along the skid trial.

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80
Figure 4. Tree sections indicating the damage location
classes.
Figure 5. Blue-stain defects discoloring the woods after the
stand damage.
Damage Sizes
The size of the damages was evaluated by considering
average width, length, and area of the injury. The results
indicated that damage sizes vary depending on the logging stages
(Table 2). The statistical analysis showed that the average width
and length of the damages due to felling operation was 8.31 cm
and 28.94 cm, respectively. Since vertical felling direction is
parallel to the tree stem, damage length was generally greater
than damage width in felling operation (Figure 6).
Table 2. Statistical summary about size of the damages.
Logging
Stages
Number
of
Injuries
Average Values ± SE
Width (cm) Length (cm) Area (cm2)
Felling 16 8.31 ± 2.16 28.94 ± 8.26 376,19 ± 198,48
Skidding 40 10.87 ± 1.30 19.08 ± 2.27 307,70 ± 67,75
Total 56 10.14 ± 1.12 21.89 ± 2.88 328,82 ± 70,90
Figure 6. Thinner and longer stand damage on rs due to
felling operation.
During skidding operation, the average damage width and
length was found to be 10.87 cm and 19.08 cm, respectively.
In skidding operation, larger damage widths occurred due to
frequent contacts between skidded logs and residual trees.
However, the average damage length in skidding operation was
smaller than that of felling.
The damage size can be the most significant factor of
deterioration. Aho et al. [3] reported that the larger injuries
results in more and rapid deterioration process. The studies
indicated that wider and shorter injuries can cause more volume
loss than that of thinner and longer injuries [28]. Besides, wider
injuries can reduce the diameter growth. Isomaki and Kallio
[17] reported that damage widths of 5-10 cm and 17-35 cm
reduced the diameter growth by 10% and 35%, respectively.
Furthermore, recovery from the wider injuries takes longer
period of time than of thinner and longer injuries [26].
In Turkey, the number of injuries and damage sizes are
considerably high because logging operations are mostly
performed during summer season. However, extracting timber
during winter season can dramatically reduce the amount and
size of the residual damages [27].
Damage Types
The results indicated that about 56.14% (32 damages) of the
injuries occurred on tree barks, resulted in cambium exposed.
About 42.11% (24 damages) of the damages was seen to be
stem or wood injuries. Only 1.75% (1 damage) of the injuries
resulted in broken tops. The results also indicated that 4 out
of 24 wood injuries occurred in pines, while rest of the wood
injuries was encountered in firs [28]. Residual trees with wood
injuries become more vulnerable to insect and fungus attacks.
The average depth of the injuries on the wood was estimated to
be 2.70 ± 0.38 mm.
Isomaki and Kallio [17] indicated that the depth and size of
the injuries on the wood greatly affect the diameter growth. They
reported that diameter growth can be reduced by 10% and 20%
due to surface injuries and deep wood injuries, respectively.

M. Yilmaz and A. E. Akay / IJNES, 2 (1): 77-82, 2008 81
CONCLUSIONS
The residual stand damages from a logging operation was
studied in an uneven-aged mixed forest to examine the effects of
various factors such as logging stages, tree species, and location,
size, and type of damages. In an uneven-aged mixed forest,
timber extraction is generally performed by selection cutting
method which may cause serious stand damages during felling
and skidding operations. Therefore, the effects of specified
factors on stand damage should be well understood to plan
proper logging operations with minimum damage. The logging
managers should implement directional felling techniques
and pre-determine straight skidding trails before entering the
stand. In extracting timber from a stand consisting of trees with
thinner barks (i.e. firs), logging operations should be carried
out with extra precautions. Tree protection tools (i.e. rub pads)
should be used to reduce damages on stump level and stem level
sections. In felling and skidding operations, damage size should
be kept as small as possible to minimize potential deterioration
on wood due to attacks of biotic agents. The loggers should
be well educated about the important functions of uneven-aged
mixed forests in sustainability of forest ecosystem. Then, these
adequately trained and supervised loggers should be employed
in selection cutting operations to reduce stand damage.
Finally, adequate logging activities should be applied as a
tool of silvicultural treatment in maintaining and ensuring the
significant value and functions of uneven-aged mixed forest.
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