Investigation of timber harvesting impac
ARTICLE IN PRESS
Building and Environment 42 (2007) 1194–1199
www.elsevier.com/locate/buildenv
Investigation of timber harvesting impacts on herbaceous cover,
forest floor and surface soil properties on skid road
in an oak (Quercus petrea L.) stand
Murat Demira,, Ender Makinecib, Ersel Yilmazc
a
Department of Forest Construction and Transportation, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey
b
Department of Soil Science and Ecology, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey
c
Department of Forest Yield and Biometry, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey
Received 13 October 2005; received in revised form 8 November 2005; accepted 11 November 2005
Abstract
In this study, we investigated the timber harvesting effects on some soil properties (sand, silt, clay, pH, electrical conductivity, fine soil
o2 mm, coarse soil 42 mm, root mass, organic carbon, moisture equivalent, total porosity, bulk density, moisture and compaction) at
soil depths (0–5 and 5–10 cm), herbaceous cover and forest floor (unit mass, organic matter and moisture) on skid road of an oak
(Quercus petrea L.) stand in Istanbul Belgrad Forest of Turkey.
According to the results obtained, the forest floor and the herbaceous cover amount on the skid road have considerably decreased.
There has been some crucial changes in the characteristics of the soil, which has been investigated down to 10 cm depth. The fine soil
weight and bulk density values were found to be quite high in the samples taken from the skid road subjected to compaction compared to
the ones in the undisturbed area; also the porosity and moisture equivalent values decreased to a great extent. Nevertheless, no important
difference has been detected between the skid road and the undisturbed area at both soil depths in terms of organic carbon rates.
Moreover, the soil acidity (pH) values have shown noteworthy differences in the analysis of soil samples taken from both soil depths, on
the skid road and in the undisturbed area.
r 2005 Elsevier Ltd. All rights reserved.
Keywords: Harvesting impacts; Skidding; Skid road; Soil; Herbaceous cover; Forest floor
1. Introduction
Harvesting works being carried out in the forest areas
causes losses, mixing and compaction of the soil to a great
extent. Degradation in the soil after timber harvesting also
has as much important effects on the contents of nutrients
as it has impact on the physical properties of the soil [1–9].
Subject to this, tree development falls considerably [8–14].
Moreover, compaction and loss through erosion of the
upper soil layer, which is rich in organic matters and
Corresponding author. Tel.: +90 212 2261100/x25289;
fax: +90 212 2261113.
E-mail addresses: mdemir@istanbul.edu.tr,
muratdemir1973@yahoo.com (M. Demir), emak@istanbul.edu.tr
(E. Makineci), ersel@istanbul.edu.tr (E. Yilmaz).
0360-1323/$ - see front matter r 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.buildenv.2005.11.008
nutrients, brings down the efficiency of the forest [3,15–18].
The soil is a habitat for the plant roots and numerous
viruses, bacteria, fungi, algae and other soil organisms.
Skidding works carried out in the forests have negative
impacts on the variety of the soil’s biological communities
and conditions thereof through effects such as decrease of
organic matters, compaction, change in the flora and soil
microclimate [1,10–12,19–21]. The dimension of the impact
created by skidding of the products directly on the ground
varies according to many factors such as slope, site
characteristics, production methods used, planning of skid
roads and production season. Skidding of the harvested
products directly on the ground compresses the soil and
results in changes in the structural properties of the soil.
Such changes directly affect the water-holding capacity,
soil aeration, drainage and root development in the soil.
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
Major deficiencies caused by the skid roads are determined
as loss of organic matters from the forest floor and
aboveground level, compaction and exposition to erosion
of the soil. These detriments also affect infiltration of water
into the soil and pass through to the lower levels.
The aim of this study is to examine the impacts of
production works, which have been carried out for many
years, on some herbaceous covers, forest floors and soil
properties on the skid road in a given oak (Quercus petrea
L.) stand in Istanbul Belgrad Forest of Turkey.
1195
activities on the skidding road [22]. Altitude is 140 m,
slope is 10–15% and it is in the SW aspect. The skid road
passing through the stand in East–West direction has long
been used (since 1956) in the production works. Skidding
works in the research area are being carried out by
manpower, animal power and machinery. Herbaceous
vegetation species are Hedera helix L., Ruscus aculeatus
L., Ruscus hypoglossum L., Rubus ssp, Viola ssp L., Galium
odoratum (L.) Scop., Salvia forskahlei L., Trachystemon
orientale (L.) G. Don. on the skid road and undisturbed
area. In this study, the impacts of skidding on the skid road
that has been used for a long time, the forest floor,
herbaceous cover and the surface soil layer (down to 10 cm
depth) thereof have been examined, in comparison to the
undisturbed area. The skid road was sampled at seven
different points at 10-m intervals for this purpose (seven
samples were taken from each of herbaceous cover, forest
floor, 0–5 cm soil and 5–10 cm soil). Moreover, for control
purpose, soil, forest floor and herbaceous cover samples
from seven different points were taken again at 10-m
intervals (seven samples from each of the herbaceous cover,
forest floor, 0–5 and 5–10 cm soil) from the undisturbed
area where there is no skidding impact and at least 25–30 m
away from the skid road (at least one tree length away to
reduce side impacts). Herbaceous cover samples were taken
by cutting aboveground parts of all herbaceous cover in
1 m2 area and the samples of the forest floor were taken
from 14 m2 (0.25 m2) area by collecting all the forest floor in
that area. Soil compaction at the places where herbaceous
cover and forest floor samples were taken was measured at
two different soil depths (0–5 and 5–10 cm) by using a
2. Material and methods
Belgrad Forest is located in Istanbul province in the
Marmara geographical region between 411090 N and
411120 N latitudes and 281540 E and 291000 E longitudes
and covers an area of 5441.71 ha (Fig. 1). The research area
is in the boundaries of zone 82 of Belgrad Forest.
According to the (long-term) data given by Bahcekoy
Meteorology Station, the closest meteorology station to the
research area, average annual precipitation is 1074.4 mm,
annual mean temperature is 12.8 1C, mean high temperature is 17.8 1C and the average low temperature is 9 1C. The
climate of Istanbul Belgrad Forest is close to sea (ocean)
climate with medium water deficit in summers. Vegetation
period maintains for 7.5 months (230 days) on average.
Research area is a pure sessile oak (Quercus petrea L.)
stand. Canopy cover has been estimated as 0.8. Average
diameter is 29.72 cm, average height is 22.94 m and stand
density has been measured as 900 trees/ha. It was estimated
that 195 m3 timbers was skidded annually in harvest
THE LOCATION
OF ISTANBUL
BELGRAD
FOREST IN
TURKEY
BLACK SEA
Kilyos
Sariyer
BELGRAD
FOREST
Beykoz
Istinye
Rumelihisari
Anadoluhisari
Ortakoy
26 ºE
ISTANBUL
BULGARIA
Uskudar
45 ºE
BLACK SEA
42 ºN
42 ºN
GEORGIA
ARMENIA
AZERBAIJAN
Bakirkoy
Kadikoy
GREECE
Yesilkoy
RUSSIA
TURKEY
IRAN
AEGEAN SEA
MARMARA SEA
N
36ºN
36 ºN
SYRIA
IRAQ
MEDITERREAN SEA
Research Area
0
2
4
6 km
0
250 500km
26 ºE
Fig. 1. The location of Istanbul Belgrad Forest in Turkey.
45ºE
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
pocket penetrometer. Soil samples were taken from 0–5
and 5–10 cm with the aid 100 cm3 steel soil cylinders. A
total of 300 cm3 soil sample was taken for each of the soils
depths of the sampling points. All samples were collected in
September 2004 and put in polyethylene bags and labeled.
Samples brought to the laboratory from the research area
were promptly weighed (within 1 h) and percentage of
moisture and weight values of oven dried samples were
calculated from the difference between the values of wet
and oven-dried samples after making the herbaceous cover
samples dried under 65 1C and forest floor and soil samples
dried under 105 1C for 24 h in an oven. All weight values
given in relevant tables about herbaceous cover, forest
floor and soil samples are oven-dried values. Organic
matter amounts of the herbaceous cover and forest floor
samples were found by loss on ignition method after
grinding and burning at 550 1C. Soil samples were sieved
through 2 mm sieves and thus, fine soil (o2 mm), root
(roots were weighed after rinsing with distilled water and
waiting under 105 1C for 24 h) and coarse soil fraction
(42 mm) weights were found. Sand, silt and clay ratio of
soil samples in the laboratory were found by Bouyoucos
hydrometer method. Organic carbon ratio was determined
by Walkey and Black wet digestion method. Also weight of
fine soil (o2 mm) and 42 mm soil fraction weight, bulk
density, total porosity, moisture equivalence, pH and
electrical conductivity values were measured in the
laboratory as described in Karao¨z [23–25]. The values
found for the undisturbed area and for the skid road were
compared statistically at 0.05 significance level by using
independent sample t-test statistical analysis. Mean values
found for all properties are shown in relevant tables.
3. Results and discussion
3.1. Properties of herbaceous cover
Aboveground amount of the total herbaceous cover in
unit area is 240.18 kg ha 1 on the skid road and
702.60 kg ha 1 in the undisturbed area (Table 1). The
undisturbed area has considerably more amount of
herbaceous cover than the skid road. It is estimated that
the greatest impact in decrease of herbaceous cover on the
skid road is sourcing from the damage the skidding timbers
cause on the herbaceous cover. Moreover, the changing
properties of the soil and forest floor after skidding may
directly or indirectly can be effective in decreasing
herbaceous cover. The mean organic matter rate in the
undisturbed area and the skid road is considerably
different (Table 2) and organic matter rate of the
herbaceous cover (91.12%) on the skid road is considerably
higher than that of the undisturbed area (86.26%). This
situation may most probably source from the difference
among the herbaceous plant species. Changing conditions
on the skid road can be effective in decreasing and
changing the kind of species, compared to the undisturbed
area. Results of previous similar studies show that there is a
Table 1
Herbaceous cover properties
Characteristics
Skid road Undisturbed Asymp. Sig. 2-tailed
240.18a
Herbaceous mass
(kg ha 1)
Moisture (%)
67.67a
Organic matter (%)
91.12a
Organic matter (kg ha 1) 218.87a
702.60b
0.006
**
71.12a
86.26b
615.95b
0.371
0.030
0.011
NS
*
*
Values are mean. Significance levels are NS non-significant, *0.05–0.01
and **0.01–0.001, values within columns followed by the same letter are
not statistically different at 0.05 significance level.
Table 2
Forest floor properties
Characteristics
Skid road Undisturbed Asymp. Sig. 2tailed
Forest floor mass (kg ha 1)
Moisture (%)
Organic matter (%)
Organic matter (kg ha 1)
2886.86a
35.42a
85.58a
2449.24a
4532.76b
48.45b
89.37a
4037.76b
0.011
0.019
0.203
0.004
*
*
NS
**
Values are mean. Significance levels are NS non-significant, *0.05–0.01
and **0.01–0.001, values within columns followed by the same letter are
not statistically different at 0.05 significance level.
difference between the skid roads and undisturbed areas in
the kind of herbaceous species [2,4,20]. However, a
comprehensive herbaceous species determination has not
been made in this study. Subject to both differences
between the organic matter rates (%) and also differences
in the aboveground masses of herbaceous cover, the
organic matter amount in the herbaceous cover unit area
is considerably different on the skid road and in the
undisturbed area. Higher organic matter amount in unit
area has been detected in the undisturbed area (615.95 kg
ha 1) (Table 1). Noteworthy difference could not be found
in terms of moisture rates (Table 1). Similar to our findings
in this research, many researchers have also set forth the
negative impacts of skidding on the herbaceous cover
[2,4,6,13,20].
3.2. Properties of forest floor
Total forest floor weight in unit area in the undisturbed
area is 4532.76 kg ha 1 and on the skid road
2886.86 kg ha 1 (Table 2). The undisturbed area has
considerably higher amount of forest floor. Less forest
floor on the skid road shows that the forest floor has been
moved out by skidding. In addition, some of the trees along
the skidding route are cut during building of the skid roads
in order to prevent any preclusion on skidding works and
to have a straight skid road. Therefore, the number of trees
per unit area on the skid road decreases. It is also estimated
that, subject to the decreasing number of trees, amount of
litter fall is also decreasing. There is no important
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
difference between the organic matter rates on the skid
road (85.58%) and in the undisturbed area (89.37%)
(Table 2). Depending on the considerable difference in the
forest floor amounts, organic matter amounts (kg ha 1) in
unit area also show important differences and the values in
the undisturbed area (4037.76 kg ha 1) are much higher
than the value taken from the skid road (2449.24 kg ha 1)
(Table 2). The fact that there is no important difference
between the forest floor organic matter rates can be
explained as the presence of the last year’s leaves in the
forest floor both in the undisturbed area and on the skid
road for the reason of fast decomposing oak forest floor
[26,27]. Mean moisture rate of forest floor in the
undisturbed area (48.45%) has been found considerably
higher than that of the skid road (35.42%) (Table 2). The
reason why there are crucial moisture differences in the
forest floor of the undisturbed area and the skid road may
be holding of less moisture subject to the decreasing forest
floor. Another reason of this may be losing the rain waters
because of rapid penetration down to the mineral soil
without being held in the forest floor subject to the
decreasing forest floor and thickness as well as loosing the
same because of surface flows and evaporation. Impacts of
skidding and production works on the forest floor
characteristics show similar results in many researches
[1,6,10–12,19,21].
3.3. Soil properties
3.3.1. 0–5 cm soil depth
The sample soil taken from 0–5 cm depth showed
important differences in the undisturbed area and on the
skid road with regard to some properties such as sand %,
clay %, pH, fine soil (o2 mm) weight, moisture equivalent
Table 3
Investigated soil properties in 0–5 cm soil depth
Characteristics
Skid road Undisturbed Asymp. Sig. 2-tailed
Sand (%)
Silt (%)
Clay (%)
pH
Electrical conductivity
(mhos cm 1)
Fine soil (o2 mm) weight
(g cm 3)
Coarse soil (42 mm)
weight (g cm 3)
Root mass (g cm 3)
Organic carbon (%)
Moisture equivalent (%)
Total porosity (%)
Moisture (%)
Compaction (kg cm 2)
Bulk density (g cm 3)
73.37a
18.04a
8.59a
6.23a
86.57a
67.77b
16.28a
15.95b
5.61b
88.35a
0.032
0.508
0.000
0.040
0.899
*
NS
***
*
NS
0.887a
0.479b
0.000
***
0.13a
0.117a
0.617
NS
0.062
0.162
0.000
0.000
0.994
0.000
0.001
NS
NS
***
***
NS
***
**
0.00336a 0.00679a
9.75a
7.97a
a
22.58
28.88b
59.19b
47.84a
a
22.04
22.06a
2.71a
1.37b
a
1.028
0.635b
Values are mean. Significance levels are NS non-significant, *0.05–0.01,
**0.01–0.001 and ***0.0014, values within columns followed by the same
letter are not statistically different at 0.05 significance level.
1197
%, total porosity %, compaction and bulk density values
(Table 3). Average compaction value on the skid road has
been measured as 2.71 kg cm 2 on the skid road and
1.37 kg cm 2 in the undisturbed area (Table 3). 0–5 cm soil
depth on the skid road is substantially compacted in
comparison with the undisturbed area. Depending on the
compaction of the soil, considerable differences were found
between the undisturbed area and the skid road with regard
to the soil bulk density, fine soil weight, total porosity and
moisture equivalent values (Table 3). Soil bulk density
(1.028 g cm 3) and fine soil weight (0.887 g cm 3) on the
skid road because of compaction are quite higher than
those in the undisturbed area (0.636 and 0.479 g cm 3,
respectively) (Table 3). Similarly, the values of total
porosity (47.84%) and moisture equivalent (22.58%) on
the skid road subject to compaction are considerably lower
than the total porosity (59.19%) and the moisture
equivalent (28.88%) in the undisturbed area (Table 3).
Mean sand rate (73.37%) on the skid road which is quite
higher and the mean clay rate (8.59%) which is lower on
the skid road than in the undisturbed area have been found
(Table 3). The reason of the important differences in the
sand and clay rates may be the changes in the natural
structure of the soil subject to soil compaction along with
possible surface flows and erosion effects. The soil acidity
(pH 6.23) at 0–5 cm depth on the skid road is higher to a
great degree than the one in the undisturbed area (pH 5.61)
(Table 3). In addition to the changes in the soil properties,
subject to the decreasing forest floor and herbaceous cover,
changes in the properties of the decomposing organic
matter can be effective on the acidity of the soil. Moreover,
it is estimated that possible surface flows and erosion
carrying as well as accumulation because of sedimentation
are also effective on the soil acidity.
No important differences could be found between the
skid road and undisturbed area values with regard to other
soil properties we have examined characteristics such as silt
%, electrical conductivity, soil fraction greater than 2 mm,
root mass, organic carbon and moisture rates (Table 4).
3.3.2. 5–10 cm soil depth
Results for the soil samples taken from 5 to 10 cm depth
are similar to the results we found for 0–5 cm depth except
for the silt and clay ratios (Table 4). Nevertheless, different
from the 0–5 cm soil depth, no considerable differences
could be found in the clay rates between the undisturbed
area and the skid road (Table 4). Furthermore, it has been
observed that the silt rate of the skid road is quite higher
compared to the silt rate of the undisturbed area (Table 4).
Likely cause of these changes in the sand, silt and clay rates
must be, subject to the soil compaction, the change in the
natural soil structure before the skidding works. Because of
the soil compaction, much higher bulk density
(1.235 g cm 3) and fine soil weight (0.784 g cm 3) values
and also much lower total porosity (45.52%) and moisture
equivalence (21.57%) were found on the skid road compared
to the undisturbed area because of soil compaction on the
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
1198
Table 4
Investigated soil properties in 5–10 cm soil depth
Characteristics
Skid road Undisturbed Asymp. Sig. 2-tailed
Sand (%)
Silt (%)
Clay (%)
pH
Electrical conductivity
(mhos cm 1)
Fine soil (o2 mm) weight
(g cm 3)
Coarse soil (42 mm)
weight (g cm 3)
Root mass (g cm 3)
Organic carbon (%)
Moisture equivalent (%)
Total porosity (%)
Moisture (%)
Compaction (kg cm 2)
Bulk density (g cm 3)
58.04a
25.74a
16.22a
5.80a
60.05a
73.52b
10.86b
15.62a
5.25b
67.18a
0.003
0.000
0.754
0.042
0.446
**
***
NS
*
NS
1.015a
0.571b
0.000
***
0.215a
0.144a
0.279
NS
0.085
0.085
0.001
0.000
0.939
0.000
0.000
NS
NS
**
***
NS
***
***
0.01904a 0.02507a
5.72a
7.53a
a
25.07b
21.57
57.24b
45.52a
a
19.71a
19.85
3.37a
1.85b
a
1.235
0.784b
Values are mean. Significance levels are NS non-significant, *0.05–0.01,
**0.01–0.001 and ***0.0014, values within columns followed by the same
letter are not statistically different at 0.05 significance level.
skid road at 5–10 cm depth (Table 4). Because of the
compaction that occurred on the skid road after skidding,
the fine soil weight and bulk density values increased.
Depending on the decrease in the total porosity after
compaction, the moisture equivalent decreased. These
consequences are the impacts that directly affect and
decrease water and air economy of the soil. In addition to
these important changes in the soil properties, it is estimated
that the variations in the decomposition conditions sourcing
from decrease in the forest floor and herbaceous cover are
also effective in affecting pH of the soil. This important
difference determined with regard to the soil acidity can be
interpreted as the conditions that change after skidding may
also be effective on the soil chemistry. In fact, many
researches state that the skidding impacts cause changes in
the chemical properties of the soil [1,6,9–12].
Soil properties which we have examined 5–10 cm depth
(electrical conductivity, soil fraction 42 mm, root, organic
carbon and moisture) do not show noteworthy differences
between the skid road and the undisturbed area (Table 4).
Similar skidding and harvesting activities in the forestry
applications generally increases compaction of the soil.
Crucial changes may occur on the physical factors that
affect the higher bulk density, lower porosity and waterholding capacity of the soil because of compaction of the
soil [1–10,13,16,28]. Despite our findings at both soil
depths, it is generally claimed that the skidding works
cause decrease in organic matter amount in the soil.
[7,9–11,19,21].
4. Conclusions
In this study, we have tried to put forward the impacts of
skidding works, which have been carried out for many
years on a skid road in an oak (Quercus petrea L.) stand, on
the topsoil properties, forest floor and herbaceous cover.
The skidding works that have been carried out caused
decrease in the forest floor and the herbaceous cover to a
great extent. Furthermore, the skidding has been effective
on both soil depths (0–5 and 5–10 cm) which were
examined. Compaction of soil with the impact of skidding
has caused increase in fine soil weight and bulk density
values and decrease in total porosity and moisture
equivalent rates on the skid road. Negative impacts of soil
compaction have been set forth with many researches.
Compaction of soil causes decrease in the permeability and
infiltration capacity of the soil, which leads pooling of
water on the ground and therefore loss of moisture through
evaporation [1–3,5,11–14]. Therefore, root development
slows down and subject to this, water and nutrient uptake
of the existing plants decreases. Decrease in the total
porosity and worsening of soil aeration negatively affect
aerobe soil organisms and are also effective on the life
activities of other organisms [1,12,19]. Moreover, because
of the increasing denitrification, nitrate nitrogen is lost in
the atmosphere. Thus, nitrogen losses occur in the soil by
this way [1,11]. Decreasing of infiltration and permeability
in the soil in the slope areas because of compaction can
cause erosion [3,14,15,17,18]. Lessening of the herbaceous
cover and forest floor after skidding leaves the soil
vulnerable against erosion and forest floor decomposition
and mineralization also decreases because of unfavorable
soil conditions. Thus, retardation occurs in the nutrient
cycle in the forest ecosystem [1,6,9–12,19,21].
Briefly, the long-term skidding works carried out in an
oak stand caused noteworthy losses in the herbaceous
cover and forest floor on the skid road. Additionally, soil
properties have also changed to a great extent. It is obvious
that particularly the changes which occur subject to the soil
compaction will cause negative impacts on the water and
air economies of the soils on the skid roads. Prompt actions
should be taken to prevent and minimize such negative
impacts of the skid roads. Especially, the skid roads should
not be used for long periods without taking any actions
after they are built. Making rehabilitation works [5,29,30]
on the skid roads to retain soil properties which have
drastically degraded and which have undergone erosions
and, therefore lost their plant cover shall be very useful in
terms of protection of the ecosystem.
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Building and Environment 42 (2007) 1194–1199
www.elsevier.com/locate/buildenv
Investigation of timber harvesting impacts on herbaceous cover,
forest floor and surface soil properties on skid road
in an oak (Quercus petrea L.) stand
Murat Demira,, Ender Makinecib, Ersel Yilmazc
a
Department of Forest Construction and Transportation, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey
b
Department of Soil Science and Ecology, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey
c
Department of Forest Yield and Biometry, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, Turkey
Received 13 October 2005; received in revised form 8 November 2005; accepted 11 November 2005
Abstract
In this study, we investigated the timber harvesting effects on some soil properties (sand, silt, clay, pH, electrical conductivity, fine soil
o2 mm, coarse soil 42 mm, root mass, organic carbon, moisture equivalent, total porosity, bulk density, moisture and compaction) at
soil depths (0–5 and 5–10 cm), herbaceous cover and forest floor (unit mass, organic matter and moisture) on skid road of an oak
(Quercus petrea L.) stand in Istanbul Belgrad Forest of Turkey.
According to the results obtained, the forest floor and the herbaceous cover amount on the skid road have considerably decreased.
There has been some crucial changes in the characteristics of the soil, which has been investigated down to 10 cm depth. The fine soil
weight and bulk density values were found to be quite high in the samples taken from the skid road subjected to compaction compared to
the ones in the undisturbed area; also the porosity and moisture equivalent values decreased to a great extent. Nevertheless, no important
difference has been detected between the skid road and the undisturbed area at both soil depths in terms of organic carbon rates.
Moreover, the soil acidity (pH) values have shown noteworthy differences in the analysis of soil samples taken from both soil depths, on
the skid road and in the undisturbed area.
r 2005 Elsevier Ltd. All rights reserved.
Keywords: Harvesting impacts; Skidding; Skid road; Soil; Herbaceous cover; Forest floor
1. Introduction
Harvesting works being carried out in the forest areas
causes losses, mixing and compaction of the soil to a great
extent. Degradation in the soil after timber harvesting also
has as much important effects on the contents of nutrients
as it has impact on the physical properties of the soil [1–9].
Subject to this, tree development falls considerably [8–14].
Moreover, compaction and loss through erosion of the
upper soil layer, which is rich in organic matters and
Corresponding author. Tel.: +90 212 2261100/x25289;
fax: +90 212 2261113.
E-mail addresses: mdemir@istanbul.edu.tr,
muratdemir1973@yahoo.com (M. Demir), emak@istanbul.edu.tr
(E. Makineci), ersel@istanbul.edu.tr (E. Yilmaz).
0360-1323/$ - see front matter r 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.buildenv.2005.11.008
nutrients, brings down the efficiency of the forest [3,15–18].
The soil is a habitat for the plant roots and numerous
viruses, bacteria, fungi, algae and other soil organisms.
Skidding works carried out in the forests have negative
impacts on the variety of the soil’s biological communities
and conditions thereof through effects such as decrease of
organic matters, compaction, change in the flora and soil
microclimate [1,10–12,19–21]. The dimension of the impact
created by skidding of the products directly on the ground
varies according to many factors such as slope, site
characteristics, production methods used, planning of skid
roads and production season. Skidding of the harvested
products directly on the ground compresses the soil and
results in changes in the structural properties of the soil.
Such changes directly affect the water-holding capacity,
soil aeration, drainage and root development in the soil.
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
Major deficiencies caused by the skid roads are determined
as loss of organic matters from the forest floor and
aboveground level, compaction and exposition to erosion
of the soil. These detriments also affect infiltration of water
into the soil and pass through to the lower levels.
The aim of this study is to examine the impacts of
production works, which have been carried out for many
years, on some herbaceous covers, forest floors and soil
properties on the skid road in a given oak (Quercus petrea
L.) stand in Istanbul Belgrad Forest of Turkey.
1195
activities on the skidding road [22]. Altitude is 140 m,
slope is 10–15% and it is in the SW aspect. The skid road
passing through the stand in East–West direction has long
been used (since 1956) in the production works. Skidding
works in the research area are being carried out by
manpower, animal power and machinery. Herbaceous
vegetation species are Hedera helix L., Ruscus aculeatus
L., Ruscus hypoglossum L., Rubus ssp, Viola ssp L., Galium
odoratum (L.) Scop., Salvia forskahlei L., Trachystemon
orientale (L.) G. Don. on the skid road and undisturbed
area. In this study, the impacts of skidding on the skid road
that has been used for a long time, the forest floor,
herbaceous cover and the surface soil layer (down to 10 cm
depth) thereof have been examined, in comparison to the
undisturbed area. The skid road was sampled at seven
different points at 10-m intervals for this purpose (seven
samples were taken from each of herbaceous cover, forest
floor, 0–5 cm soil and 5–10 cm soil). Moreover, for control
purpose, soil, forest floor and herbaceous cover samples
from seven different points were taken again at 10-m
intervals (seven samples from each of the herbaceous cover,
forest floor, 0–5 and 5–10 cm soil) from the undisturbed
area where there is no skidding impact and at least 25–30 m
away from the skid road (at least one tree length away to
reduce side impacts). Herbaceous cover samples were taken
by cutting aboveground parts of all herbaceous cover in
1 m2 area and the samples of the forest floor were taken
from 14 m2 (0.25 m2) area by collecting all the forest floor in
that area. Soil compaction at the places where herbaceous
cover and forest floor samples were taken was measured at
two different soil depths (0–5 and 5–10 cm) by using a
2. Material and methods
Belgrad Forest is located in Istanbul province in the
Marmara geographical region between 411090 N and
411120 N latitudes and 281540 E and 291000 E longitudes
and covers an area of 5441.71 ha (Fig. 1). The research area
is in the boundaries of zone 82 of Belgrad Forest.
According to the (long-term) data given by Bahcekoy
Meteorology Station, the closest meteorology station to the
research area, average annual precipitation is 1074.4 mm,
annual mean temperature is 12.8 1C, mean high temperature is 17.8 1C and the average low temperature is 9 1C. The
climate of Istanbul Belgrad Forest is close to sea (ocean)
climate with medium water deficit in summers. Vegetation
period maintains for 7.5 months (230 days) on average.
Research area is a pure sessile oak (Quercus petrea L.)
stand. Canopy cover has been estimated as 0.8. Average
diameter is 29.72 cm, average height is 22.94 m and stand
density has been measured as 900 trees/ha. It was estimated
that 195 m3 timbers was skidded annually in harvest
THE LOCATION
OF ISTANBUL
BELGRAD
FOREST IN
TURKEY
BLACK SEA
Kilyos
Sariyer
BELGRAD
FOREST
Beykoz
Istinye
Rumelihisari
Anadoluhisari
Ortakoy
26 ºE
ISTANBUL
BULGARIA
Uskudar
45 ºE
BLACK SEA
42 ºN
42 ºN
GEORGIA
ARMENIA
AZERBAIJAN
Bakirkoy
Kadikoy
GREECE
Yesilkoy
RUSSIA
TURKEY
IRAN
AEGEAN SEA
MARMARA SEA
N
36ºN
36 ºN
SYRIA
IRAQ
MEDITERREAN SEA
Research Area
0
2
4
6 km
0
250 500km
26 ºE
Fig. 1. The location of Istanbul Belgrad Forest in Turkey.
45ºE
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
pocket penetrometer. Soil samples were taken from 0–5
and 5–10 cm with the aid 100 cm3 steel soil cylinders. A
total of 300 cm3 soil sample was taken for each of the soils
depths of the sampling points. All samples were collected in
September 2004 and put in polyethylene bags and labeled.
Samples brought to the laboratory from the research area
were promptly weighed (within 1 h) and percentage of
moisture and weight values of oven dried samples were
calculated from the difference between the values of wet
and oven-dried samples after making the herbaceous cover
samples dried under 65 1C and forest floor and soil samples
dried under 105 1C for 24 h in an oven. All weight values
given in relevant tables about herbaceous cover, forest
floor and soil samples are oven-dried values. Organic
matter amounts of the herbaceous cover and forest floor
samples were found by loss on ignition method after
grinding and burning at 550 1C. Soil samples were sieved
through 2 mm sieves and thus, fine soil (o2 mm), root
(roots were weighed after rinsing with distilled water and
waiting under 105 1C for 24 h) and coarse soil fraction
(42 mm) weights were found. Sand, silt and clay ratio of
soil samples in the laboratory were found by Bouyoucos
hydrometer method. Organic carbon ratio was determined
by Walkey and Black wet digestion method. Also weight of
fine soil (o2 mm) and 42 mm soil fraction weight, bulk
density, total porosity, moisture equivalence, pH and
electrical conductivity values were measured in the
laboratory as described in Karao¨z [23–25]. The values
found for the undisturbed area and for the skid road were
compared statistically at 0.05 significance level by using
independent sample t-test statistical analysis. Mean values
found for all properties are shown in relevant tables.
3. Results and discussion
3.1. Properties of herbaceous cover
Aboveground amount of the total herbaceous cover in
unit area is 240.18 kg ha 1 on the skid road and
702.60 kg ha 1 in the undisturbed area (Table 1). The
undisturbed area has considerably more amount of
herbaceous cover than the skid road. It is estimated that
the greatest impact in decrease of herbaceous cover on the
skid road is sourcing from the damage the skidding timbers
cause on the herbaceous cover. Moreover, the changing
properties of the soil and forest floor after skidding may
directly or indirectly can be effective in decreasing
herbaceous cover. The mean organic matter rate in the
undisturbed area and the skid road is considerably
different (Table 2) and organic matter rate of the
herbaceous cover (91.12%) on the skid road is considerably
higher than that of the undisturbed area (86.26%). This
situation may most probably source from the difference
among the herbaceous plant species. Changing conditions
on the skid road can be effective in decreasing and
changing the kind of species, compared to the undisturbed
area. Results of previous similar studies show that there is a
Table 1
Herbaceous cover properties
Characteristics
Skid road Undisturbed Asymp. Sig. 2-tailed
240.18a
Herbaceous mass
(kg ha 1)
Moisture (%)
67.67a
Organic matter (%)
91.12a
Organic matter (kg ha 1) 218.87a
702.60b
0.006
**
71.12a
86.26b
615.95b
0.371
0.030
0.011
NS
*
*
Values are mean. Significance levels are NS non-significant, *0.05–0.01
and **0.01–0.001, values within columns followed by the same letter are
not statistically different at 0.05 significance level.
Table 2
Forest floor properties
Characteristics
Skid road Undisturbed Asymp. Sig. 2tailed
Forest floor mass (kg ha 1)
Moisture (%)
Organic matter (%)
Organic matter (kg ha 1)
2886.86a
35.42a
85.58a
2449.24a
4532.76b
48.45b
89.37a
4037.76b
0.011
0.019
0.203
0.004
*
*
NS
**
Values are mean. Significance levels are NS non-significant, *0.05–0.01
and **0.01–0.001, values within columns followed by the same letter are
not statistically different at 0.05 significance level.
difference between the skid roads and undisturbed areas in
the kind of herbaceous species [2,4,20]. However, a
comprehensive herbaceous species determination has not
been made in this study. Subject to both differences
between the organic matter rates (%) and also differences
in the aboveground masses of herbaceous cover, the
organic matter amount in the herbaceous cover unit area
is considerably different on the skid road and in the
undisturbed area. Higher organic matter amount in unit
area has been detected in the undisturbed area (615.95 kg
ha 1) (Table 1). Noteworthy difference could not be found
in terms of moisture rates (Table 1). Similar to our findings
in this research, many researchers have also set forth the
negative impacts of skidding on the herbaceous cover
[2,4,6,13,20].
3.2. Properties of forest floor
Total forest floor weight in unit area in the undisturbed
area is 4532.76 kg ha 1 and on the skid road
2886.86 kg ha 1 (Table 2). The undisturbed area has
considerably higher amount of forest floor. Less forest
floor on the skid road shows that the forest floor has been
moved out by skidding. In addition, some of the trees along
the skidding route are cut during building of the skid roads
in order to prevent any preclusion on skidding works and
to have a straight skid road. Therefore, the number of trees
per unit area on the skid road decreases. It is also estimated
that, subject to the decreasing number of trees, amount of
litter fall is also decreasing. There is no important
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
difference between the organic matter rates on the skid
road (85.58%) and in the undisturbed area (89.37%)
(Table 2). Depending on the considerable difference in the
forest floor amounts, organic matter amounts (kg ha 1) in
unit area also show important differences and the values in
the undisturbed area (4037.76 kg ha 1) are much higher
than the value taken from the skid road (2449.24 kg ha 1)
(Table 2). The fact that there is no important difference
between the forest floor organic matter rates can be
explained as the presence of the last year’s leaves in the
forest floor both in the undisturbed area and on the skid
road for the reason of fast decomposing oak forest floor
[26,27]. Mean moisture rate of forest floor in the
undisturbed area (48.45%) has been found considerably
higher than that of the skid road (35.42%) (Table 2). The
reason why there are crucial moisture differences in the
forest floor of the undisturbed area and the skid road may
be holding of less moisture subject to the decreasing forest
floor. Another reason of this may be losing the rain waters
because of rapid penetration down to the mineral soil
without being held in the forest floor subject to the
decreasing forest floor and thickness as well as loosing the
same because of surface flows and evaporation. Impacts of
skidding and production works on the forest floor
characteristics show similar results in many researches
[1,6,10–12,19,21].
3.3. Soil properties
3.3.1. 0–5 cm soil depth
The sample soil taken from 0–5 cm depth showed
important differences in the undisturbed area and on the
skid road with regard to some properties such as sand %,
clay %, pH, fine soil (o2 mm) weight, moisture equivalent
Table 3
Investigated soil properties in 0–5 cm soil depth
Characteristics
Skid road Undisturbed Asymp. Sig. 2-tailed
Sand (%)
Silt (%)
Clay (%)
pH
Electrical conductivity
(mhos cm 1)
Fine soil (o2 mm) weight
(g cm 3)
Coarse soil (42 mm)
weight (g cm 3)
Root mass (g cm 3)
Organic carbon (%)
Moisture equivalent (%)
Total porosity (%)
Moisture (%)
Compaction (kg cm 2)
Bulk density (g cm 3)
73.37a
18.04a
8.59a
6.23a
86.57a
67.77b
16.28a
15.95b
5.61b
88.35a
0.032
0.508
0.000
0.040
0.899
*
NS
***
*
NS
0.887a
0.479b
0.000
***
0.13a
0.117a
0.617
NS
0.062
0.162
0.000
0.000
0.994
0.000
0.001
NS
NS
***
***
NS
***
**
0.00336a 0.00679a
9.75a
7.97a
a
22.58
28.88b
59.19b
47.84a
a
22.04
22.06a
2.71a
1.37b
a
1.028
0.635b
Values are mean. Significance levels are NS non-significant, *0.05–0.01,
**0.01–0.001 and ***0.0014, values within columns followed by the same
letter are not statistically different at 0.05 significance level.
1197
%, total porosity %, compaction and bulk density values
(Table 3). Average compaction value on the skid road has
been measured as 2.71 kg cm 2 on the skid road and
1.37 kg cm 2 in the undisturbed area (Table 3). 0–5 cm soil
depth on the skid road is substantially compacted in
comparison with the undisturbed area. Depending on the
compaction of the soil, considerable differences were found
between the undisturbed area and the skid road with regard
to the soil bulk density, fine soil weight, total porosity and
moisture equivalent values (Table 3). Soil bulk density
(1.028 g cm 3) and fine soil weight (0.887 g cm 3) on the
skid road because of compaction are quite higher than
those in the undisturbed area (0.636 and 0.479 g cm 3,
respectively) (Table 3). Similarly, the values of total
porosity (47.84%) and moisture equivalent (22.58%) on
the skid road subject to compaction are considerably lower
than the total porosity (59.19%) and the moisture
equivalent (28.88%) in the undisturbed area (Table 3).
Mean sand rate (73.37%) on the skid road which is quite
higher and the mean clay rate (8.59%) which is lower on
the skid road than in the undisturbed area have been found
(Table 3). The reason of the important differences in the
sand and clay rates may be the changes in the natural
structure of the soil subject to soil compaction along with
possible surface flows and erosion effects. The soil acidity
(pH 6.23) at 0–5 cm depth on the skid road is higher to a
great degree than the one in the undisturbed area (pH 5.61)
(Table 3). In addition to the changes in the soil properties,
subject to the decreasing forest floor and herbaceous cover,
changes in the properties of the decomposing organic
matter can be effective on the acidity of the soil. Moreover,
it is estimated that possible surface flows and erosion
carrying as well as accumulation because of sedimentation
are also effective on the soil acidity.
No important differences could be found between the
skid road and undisturbed area values with regard to other
soil properties we have examined characteristics such as silt
%, electrical conductivity, soil fraction greater than 2 mm,
root mass, organic carbon and moisture rates (Table 4).
3.3.2. 5–10 cm soil depth
Results for the soil samples taken from 5 to 10 cm depth
are similar to the results we found for 0–5 cm depth except
for the silt and clay ratios (Table 4). Nevertheless, different
from the 0–5 cm soil depth, no considerable differences
could be found in the clay rates between the undisturbed
area and the skid road (Table 4). Furthermore, it has been
observed that the silt rate of the skid road is quite higher
compared to the silt rate of the undisturbed area (Table 4).
Likely cause of these changes in the sand, silt and clay rates
must be, subject to the soil compaction, the change in the
natural soil structure before the skidding works. Because of
the soil compaction, much higher bulk density
(1.235 g cm 3) and fine soil weight (0.784 g cm 3) values
and also much lower total porosity (45.52%) and moisture
equivalence (21.57%) were found on the skid road compared
to the undisturbed area because of soil compaction on the
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M. Demir et al. / Building and Environment 42 (2007) 1194–1199
1198
Table 4
Investigated soil properties in 5–10 cm soil depth
Characteristics
Skid road Undisturbed Asymp. Sig. 2-tailed
Sand (%)
Silt (%)
Clay (%)
pH
Electrical conductivity
(mhos cm 1)
Fine soil (o2 mm) weight
(g cm 3)
Coarse soil (42 mm)
weight (g cm 3)
Root mass (g cm 3)
Organic carbon (%)
Moisture equivalent (%)
Total porosity (%)
Moisture (%)
Compaction (kg cm 2)
Bulk density (g cm 3)
58.04a
25.74a
16.22a
5.80a
60.05a
73.52b
10.86b
15.62a
5.25b
67.18a
0.003
0.000
0.754
0.042
0.446
**
***
NS
*
NS
1.015a
0.571b
0.000
***
0.215a
0.144a
0.279
NS
0.085
0.085
0.001
0.000
0.939
0.000
0.000
NS
NS
**
***
NS
***
***
0.01904a 0.02507a
5.72a
7.53a
a
25.07b
21.57
57.24b
45.52a
a
19.71a
19.85
3.37a
1.85b
a
1.235
0.784b
Values are mean. Significance levels are NS non-significant, *0.05–0.01,
**0.01–0.001 and ***0.0014, values within columns followed by the same
letter are not statistically different at 0.05 significance level.
skid road at 5–10 cm depth (Table 4). Because of the
compaction that occurred on the skid road after skidding,
the fine soil weight and bulk density values increased.
Depending on the decrease in the total porosity after
compaction, the moisture equivalent decreased. These
consequences are the impacts that directly affect and
decrease water and air economy of the soil. In addition to
these important changes in the soil properties, it is estimated
that the variations in the decomposition conditions sourcing
from decrease in the forest floor and herbaceous cover are
also effective in affecting pH of the soil. This important
difference determined with regard to the soil acidity can be
interpreted as the conditions that change after skidding may
also be effective on the soil chemistry. In fact, many
researches state that the skidding impacts cause changes in
the chemical properties of the soil [1,6,9–12].
Soil properties which we have examined 5–10 cm depth
(electrical conductivity, soil fraction 42 mm, root, organic
carbon and moisture) do not show noteworthy differences
between the skid road and the undisturbed area (Table 4).
Similar skidding and harvesting activities in the forestry
applications generally increases compaction of the soil.
Crucial changes may occur on the physical factors that
affect the higher bulk density, lower porosity and waterholding capacity of the soil because of compaction of the
soil [1–10,13,16,28]. Despite our findings at both soil
depths, it is generally claimed that the skidding works
cause decrease in organic matter amount in the soil.
[7,9–11,19,21].
4. Conclusions
In this study, we have tried to put forward the impacts of
skidding works, which have been carried out for many
years on a skid road in an oak (Quercus petrea L.) stand, on
the topsoil properties, forest floor and herbaceous cover.
The skidding works that have been carried out caused
decrease in the forest floor and the herbaceous cover to a
great extent. Furthermore, the skidding has been effective
on both soil depths (0–5 and 5–10 cm) which were
examined. Compaction of soil with the impact of skidding
has caused increase in fine soil weight and bulk density
values and decrease in total porosity and moisture
equivalent rates on the skid road. Negative impacts of soil
compaction have been set forth with many researches.
Compaction of soil causes decrease in the permeability and
infiltration capacity of the soil, which leads pooling of
water on the ground and therefore loss of moisture through
evaporation [1–3,5,11–14]. Therefore, root development
slows down and subject to this, water and nutrient uptake
of the existing plants decreases. Decrease in the total
porosity and worsening of soil aeration negatively affect
aerobe soil organisms and are also effective on the life
activities of other organisms [1,12,19]. Moreover, because
of the increasing denitrification, nitrate nitrogen is lost in
the atmosphere. Thus, nitrogen losses occur in the soil by
this way [1,11]. Decreasing of infiltration and permeability
in the soil in the slope areas because of compaction can
cause erosion [3,14,15,17,18]. Lessening of the herbaceous
cover and forest floor after skidding leaves the soil
vulnerable against erosion and forest floor decomposition
and mineralization also decreases because of unfavorable
soil conditions. Thus, retardation occurs in the nutrient
cycle in the forest ecosystem [1,6,9–12,19,21].
Briefly, the long-term skidding works carried out in an
oak stand caused noteworthy losses in the herbaceous
cover and forest floor on the skid road. Additionally, soil
properties have also changed to a great extent. It is obvious
that particularly the changes which occur subject to the soil
compaction will cause negative impacts on the water and
air economies of the soils on the skid roads. Prompt actions
should be taken to prevent and minimize such negative
impacts of the skid roads. Especially, the skid roads should
not be used for long periods without taking any actions
after they are built. Making rehabilitation works [5,29,30]
on the skid roads to retain soil properties which have
drastically degraded and which have undergone erosions
and, therefore lost their plant cover shall be very useful in
terms of protection of the ecosystem.
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