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Building and Environment 42 (2007) 1194–1199

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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

aDepartment of Forest Construction and Transportation, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, TurkeybDepartment of Soil Science and Ecology, Faculty of Forestry, Istanbul University, 34473 Bahcekoy, Sariyer, Istanbul, TurkeycDepartment 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

o2mm, coarse soil 42mm, 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 areascauses losses, mixing and compaction of the soil to a greatextent. Degradation in the soil after timber harvesting alsohas as much important effects on the contents of nutrientsas 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 theupper soil layer, which is rich in organic matters and

e front matter r 2005 Elsevier Ltd. All rights reserved.

ildenv.2005.11.008

ing author. Tel.: +90212 2261100/x25289;

61113.

esses: mdemir@istanbul.edu.tr,

3@yahoo.com (M. Demir), emak@istanbul.edu.tr

ersel@istanbul.edu.tr (E. Yilmaz).

nutrients, brings down the efficiency of the forest [3,15–18].The soil is a habitat for the plant roots and numerousviruses, bacteria, fungi, algae and other soil organisms.Skidding works carried out in the forests have negativeimpacts on the variety of the soil’s biological communitiesand conditions thereof through effects such as decrease oforganic matters, compaction, change in the flora and soilmicroclimate [1,10–12,19–21]. The dimension of the impactcreated by skidding of the products directly on the groundvaries according to many factors such as slope, sitecharacteristics, production methods used, planning of skidroads and production season. Skidding of the harvestedproducts directly on the ground compresses the soil andresults 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.

ARTICLE IN PRESSM. Demir et al. / Building and Environment 42 (2007) 1194–1199 1195

Major deficiencies caused by the skid roads are determinedas loss of organic matters from the forest floor andaboveground level, compaction and exposition to erosionof the soil. These detriments also affect infiltration of waterinto the soil and pass through to the lower levels.

The aim of this study is to examine the impacts ofproduction works, which have been carried out for manyyears, on some herbaceous covers, forest floors and soilproperties on the skid road in a given oak (Quercus petrea

L.) stand in Istanbul Belgrad Forest of Turkey.

2. Material and methods

Belgrad Forest is located in Istanbul province in theMarmara geographical region between 411090N and411120N latitudes and 281540E and 291000E longitudesand covers an area of 5441.71 ha (Fig. 1). The research areais in the boundaries of zone 82 of Belgrad Forest.According to the (long-term) data given by BahcekoyMeteorology Station, the closest meteorology station to theresearch area, average annual precipitation is 1074.4mm,annual mean temperature is 12.8 1C, mean high tempera-ture is 17.8 1C and the average low temperature is 9 1C. Theclimate of Istanbul Belgrad Forest is close to sea (ocean)climate with medium water deficit in summers. Vegetationperiod 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. Averagediameter is 29.72 cm, average height is 22.94m and standdensity has been measured as 900 trees/ha. It was estimatedthat 195m3 timbers was skidded annually in harvest

GREE

36 ºN

RumelihisariAnadoluhisari

MARMARA SEA

Bakirkoy

Research Area

Yesilkoy

N

6 k m0 2 4 0

UskudarISTANBUL

Ortakoy

42 ºN

Kadikoy

Kilyos

Istinye

Sariyer

BELGRADFOREST

BLACK SEA

250

A

Beykoz

Fig. 1. The location of Istanbu

activities on the skidding road [22]. Altitude is 140m,slope is 10–15% and it is in the SW aspect. The skid roadpassing through the stand in East–West direction has longbeen used (since 1956) in the production works. Skiddingworks in the research area are being carried out bymanpower, animal power and machinery. Herbaceousvegetation 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 undisturbedarea. In this study, the impacts of skidding on the skid roadthat has been used for a long time, the forest floor,herbaceous cover and the surface soil layer (down to 10 cmdepth) thereof have been examined, in comparison to theundisturbed area. The skid road was sampled at sevendifferent points at 10-m intervals for this purpose (sevensamples were taken from each of herbaceous cover, forestfloor, 0–5 cm soil and 5–10 cm soil). Moreover, for controlpurpose, soil, forest floor and herbaceous cover samplesfrom seven different points were taken again at 10-mintervals (seven samples from each of the herbaceous cover,forest floor, 0–5 and 5–10 cm soil) from the undisturbedarea where there is no skidding impact and at least 25–30maway from the skid road (at least one tree length away toreduce side impacts). Herbaceous cover samples were takenby cutting aboveground parts of all herbaceous cover in1m2 area and the samples of the forest floor were takenfrom 1

4 m2 (0.25m2) area by collecting all the forest floor in

that area. Soil compaction at the places where herbaceouscover and forest floor samples were taken was measured attwo different soil depths (0–5 and 5–10 cm) by using a

CE

RUSSIA

MEDITERREAN SEA

500 km26 ºE

SYRIA

EGEAN SEA

BULGARIA

26 ºE

TURKEY

BLACK SEA

36ºN

45ºE

IRAQ

AZERBAIJAN

42 ºN

IRAN

ARMENIAGEORGIA

45 ºE

THE LOCATION OF ISTANBUL BELGRAD FOREST IN TURKEY

l Belgrad Forest in Turkey.

ARTICLE IN PRESS

Table 1

Herbaceous cover properties

Characteristics Skid road Undisturbed Asymp. Sig. 2-tailed

Herbaceous mass

(kg ha�1)

240.18a 702.60b 0.006 **

Moisture (%) 67.67a 71.12a 0.371 NS

Organic matter (%) 91.12a 86.26b 0.030 *

Organic matter (kg ha�1) 218.87a 615.95b 0.011 *

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. 2-

tailed

Forest floor mass (kg ha�1) 2886.86a 4532.76b 0.011 *

Moisture (%) 35.42a 48.45b 0.019 *

Organic matter (%) 85.58a 89.37a 0.203 NS

Organic matter (kg ha�1) 2449.24a 4037.76b 0.004 **

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.

M. Demir et al. / Building and Environment 42 (2007) 1194–11991196

pocket penetrometer. Soil samples were taken from 0–5and 5–10 cm with the aid 100 cm3 steel soil cylinders. Atotal of 300 cm3 soil sample was taken for each of the soilsdepths of the sampling points. All samples were collected inSeptember 2004 and put in polyethylene bags and labeled.Samples brought to the laboratory from the research areawere promptly weighed (within 1 h) and percentage ofmoisture and weight values of oven dried samples werecalculated from the difference between the values of wetand oven-dried samples after making the herbaceous coversamples dried under 65 1C and forest floor and soil samplesdried under 105 1C for 24 h in an oven. All weight valuesgiven in relevant tables about herbaceous cover, forestfloor and soil samples are oven-dried values. Organicmatter amounts of the herbaceous cover and forest floorsamples were found by loss on ignition method aftergrinding and burning at 550 1C. Soil samples were sievedthrough 2mm sieves and thus, fine soil (o2mm), root(roots were weighed after rinsing with distilled water andwaiting under 105 1C for 24 h) and coarse soil fraction(42mm) weights were found. Sand, silt and clay ratio ofsoil samples in the laboratory were found by Bouyoucoshydrometer method. Organic carbon ratio was determinedby Walkey and Black wet digestion method. Also weight offine soil (o2mm) and 42mm soil fraction weight, bulkdensity, total porosity, moisture equivalence, pH andelectrical conductivity values were measured in thelaboratory as described in Karaoz [23–25]. The valuesfound for the undisturbed area and for the skid road werecompared statistically at 0.05 significance level by usingindependent sample t-test statistical analysis. Mean valuesfound 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 inunit area is 240.18 kg ha�1 on the skid road and702.60 kg ha�1 in the undisturbed area (Table 1). Theundisturbed area has considerably more amount ofherbaceous cover than the skid road. It is estimated thatthe greatest impact in decrease of herbaceous cover on theskid road is sourcing from the damage the skidding timberscause on the herbaceous cover. Moreover, the changingproperties of the soil and forest floor after skidding maydirectly or indirectly can be effective in decreasingherbaceous cover. The mean organic matter rate in theundisturbed area and the skid road is considerablydifferent (Table 2) and organic matter rate of theherbaceous cover (91.12%) on the skid road is considerablyhigher than that of the undisturbed area (86.26%). Thissituation may most probably source from the differenceamong the herbaceous plant species. Changing conditionson the skid road can be effective in decreasing andchanging the kind of species, compared to the undisturbedarea. Results of previous similar studies show that there is a

difference between the skid roads and undisturbed areas inthe kind of herbaceous species [2,4,20]. However, acomprehensive herbaceous species determination has notbeen made in this study. Subject to both differencesbetween the organic matter rates (%) and also differencesin the aboveground masses of herbaceous cover, theorganic matter amount in the herbaceous cover unit areais considerably different on the skid road and in theundisturbed area. Higher organic matter amount in unitarea has been detected in the undisturbed area (615.95 kgha�1) (Table 1). Noteworthy difference could not be foundin terms of moisture rates (Table 1). Similar to our findingsin this research, many researchers have also set forth thenegative 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 undisturbedarea is 4532.76 kg ha�1 and on the skid road2886.86 kg ha�1 (Table 2). The undisturbed area hasconsiderably higher amount of forest floor. Less forestfloor on the skid road shows that the forest floor has beenmoved out by skidding. In addition, some of the trees alongthe skidding route are cut during building of the skid roadsin order to prevent any preclusion on skidding works andto have a straight skid road. Therefore, the number of treesper unit area on the skid road decreases. It is also estimatedthat, subject to the decreasing number of trees, amount oflitter fall is also decreasing. There is no important

ARTICLE IN PRESSM. Demir et al. / Building and Environment 42 (2007) 1194–1199 1197

difference between the organic matter rates on the skidroad (85.58%) and in the undisturbed area (89.37%)(Table 2). Depending on the considerable difference in theforest floor amounts, organic matter amounts (kg ha�1) inunit area also show important differences and the values inthe undisturbed area (4037.76 kg ha�1) are much higherthan the value taken from the skid road (2449.24 kg ha�1)(Table 2). The fact that there is no important differencebetween the forest floor organic matter rates can beexplained as the presence of the last year’s leaves in theforest floor both in the undisturbed area and on the skidroad for the reason of fast decomposing oak forest floor[26,27]. Mean moisture rate of forest floor in theundisturbed area (48.45%) has been found considerablyhigher than that of the skid road (35.42%) (Table 2). Thereason why there are crucial moisture differences in theforest floor of the undisturbed area and the skid road maybe holding of less moisture subject to the decreasing forestfloor. Another reason of this may be losing the rain watersbecause of rapid penetration down to the mineral soilwithout being held in the forest floor subject to thedecreasing forest floor and thickness as well as loosing thesame because of surface flows and evaporation. Impacts ofskidding and production works on the forest floorcharacteristics 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 showedimportant differences in the undisturbed area and on theskid road with regard to some properties such as sand %,clay %, pH, fine soil (o2mm) weight, moisture equivalent

Table 3

Investigated soil properties in 0–5 cm soil depth

Characteristics Skid road Undisturbed Asymp. Sig. 2-tailed

Sand (%) 73.37a 67.77b 0.032 *

Silt (%) 18.04a 16.28a 0.508 NS

Clay (%) 8.59a 15.95b 0.000 ***

pH 6.23a 5.61b 0.040 *

Electrical conductivity

(mhos cm�1)86.57a 88.35a 0.899 NS

Fine soil (o2mm) weight

(g cm�3)

0.887a 0.479b 0.000 ***

Coarse soil (42mm)

weight (g cm�3)

0.13a 0.117a 0.617 NS

Root mass (g cm�3) 0.00336a 0.00679a 0.062 NS

Organic carbon (%) 7.97a 9.75a 0.162 NS

Moisture equivalent (%) 22.58a 28.88b 0.000 ***

Total porosity (%) 47.84a 59.19b 0.000 ***

Moisture (%) 22.04a 22.06a 0.994 NS

Compaction (kg cm�2) 2.71a 1.37b 0.000 ***

Bulk density (g cm�3) 1.028a 0.635b 0.001 **

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.

%, total porosity %, compaction and bulk density values(Table 3). Average compaction value on the skid road hasbeen measured as 2.71 kg cm�2 on the skid road and1.37 kg cm�2 in the undisturbed area (Table 3). 0–5 cm soildepth on the skid road is substantially compacted incomparison with the undisturbed area. Depending on thecompaction of the soil, considerable differences were foundbetween the undisturbed area and the skid road with regardto the soil bulk density, fine soil weight, total porosity andmoisture equivalent values (Table 3). Soil bulk density(1.028 g cm�3) and fine soil weight (0.887 g cm�3) on theskid road because of compaction are quite higher thanthose in the undisturbed area (0.636 and 0.479 g cm�3,respectively) (Table 3). Similarly, the values of totalporosity (47.84%) and moisture equivalent (22.58%) onthe skid road subject to compaction are considerably lowerthan the total porosity (59.19%) and the moistureequivalent (28.88%) in the undisturbed area (Table 3).Mean sand rate (73.37%) on the skid road which is quitehigher and the mean clay rate (8.59%) which is lower onthe skid road than in the undisturbed area have been found(Table 3). The reason of the important differences in thesand and clay rates may be the changes in the naturalstructure of the soil subject to soil compaction along withpossible surface flows and erosion effects. The soil acidity(pH 6.23) at 0–5 cm depth on the skid road is higher to agreat 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 organicmatter can be effective on the acidity of the soil. Moreover,it is estimated that possible surface flows and erosioncarrying as well as accumulation because of sedimentationare also effective on the soil acidity.No important differences could be found between the

skid road and undisturbed area values with regard to othersoil properties we have examined characteristics such as silt%, electrical conductivity, soil fraction greater than 2mm,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 depthare similar to the results we found for 0–5 cm depth exceptfor the silt and clay ratios (Table 4). Nevertheless, differentfrom the 0–5 cm soil depth, no considerable differencescould be found in the clay rates between the undisturbedarea and the skid road (Table 4). Furthermore, it has beenobserved that the silt rate of the skid road is quite highercompared to the silt rate of the undisturbed area (Table 4).Likely cause of these changes in the sand, silt and clay ratesmust be, subject to the soil compaction, the change in thenatural soil structure before the skidding works. Because ofthe soil compaction, much higher bulk density(1.235 g cm�3) and fine soil weight (0.784 g cm�3) valuesand also much lower total porosity (45.52%) and moistureequivalence (21.57%) were found on the skid road comparedto the undisturbed area because of soil compaction on the

ARTICLE IN PRESS

Table 4

Investigated soil properties in 5–10 cm soil depth

Characteristics Skid road Undisturbed Asymp. Sig. 2-tailed

Sand (%) 58.04a 73.52b 0.003 **

Silt (%) 25.74a 10.86b 0.000 ***

Clay (%) 16.22a 15.62a 0.754 NS

pH 5.80a 5.25b 0.042 *

Electrical conductivity

(mhos cm�1)60.05a 67.18a 0.446 NS

Fine soil (o2mm) weight

(g cm�3)

1.015a 0.571b 0.000 ***

Coarse soil (42mm)

weight (g cm�3)

0.215a 0.144a 0.279 NS

Root mass (g cm�3) 0.01904a 0.02507a 0.085 NS

Organic carbon (%) 5.72a 7.53a 0.085 NS

Moisture equivalent (%) 21.57a 25.07b 0.001 **

Total porosity (%) 45.52a 57.24b 0.000 ***

Moisture (%) 19.85a 19.71a 0.939 NS

Compaction (kg cm�2) 3.37a 1.85b 0.000 ***

Bulk density (g cm�3) 1.235a 0.784b 0.000 ***

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.

M. Demir et al. / Building and Environment 42 (2007) 1194–11991198

skid road at 5–10 cm depth (Table 4). Because of thecompaction 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 aftercompaction, the moisture equivalent decreased. Theseconsequences are the impacts that directly affect anddecrease water and air economy of the soil. In addition tothese important changes in the soil properties, it is estimatedthat the variations in the decomposition conditions sourcingfrom decrease in the forest floor and herbaceous cover arealso effective in affecting pH of the soil. This importantdifference determined with regard to the soil acidity can beinterpreted as the conditions that change after skidding mayalso be effective on the soil chemistry. In fact, manyresearches state that the skidding impacts cause changes inthe chemical properties of the soil [1,6,9–12].

Soil properties which we have examined 5–10 cm depth(electrical conductivity, soil fraction 42mm, root, organiccarbon and moisture) do not show noteworthy differencesbetween the skid road and the undisturbed area (Table 4).

Similar skidding and harvesting activities in the forestryapplications generally increases compaction of the soil.Crucial changes may occur on the physical factors thataffect the higher bulk density, lower porosity and water-holding capacity of the soil because of compaction of thesoil [1–10,13,16,28]. Despite our findings at both soildepths, it is generally claimed that the skidding workscause 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 ofskidding works, which have been carried out for many

years on a skid road in an oak (Quercus petrea L.) stand, onthe topsoil properties, forest floor and herbaceous cover.The skidding works that have been carried out causeddecrease in the forest floor and the herbaceous cover to agreat extent. Furthermore, the skidding has been effectiveon both soil depths (0–5 and 5–10 cm) which wereexamined. Compaction of soil with the impact of skiddinghas caused increase in fine soil weight and bulk densityvalues and decrease in total porosity and moistureequivalent rates on the skid road. Negative impacts of soilcompaction have been set forth with many researches.Compaction of soil causes decrease in the permeability andinfiltration capacity of the soil, which leads pooling ofwater on the ground and therefore loss of moisture throughevaporation [1–3,5,11–14]. Therefore, root developmentslows down and subject to this, water and nutrient uptakeof the existing plants decreases. Decrease in the totalporosity and worsening of soil aeration negatively affectaerobe soil organisms and are also effective on the lifeactivities of other organisms [1,12,19]. Moreover, becauseof the increasing denitrification, nitrate nitrogen is lost inthe atmosphere. Thus, nitrogen losses occur in the soil bythis way [1,11]. Decreasing of infiltration and permeabilityin the soil in the slope areas because of compaction cancause erosion [3,14,15,17,18]. Lessening of the herbaceouscover and forest floor after skidding leaves the soilvulnerable against erosion and forest floor decompositionand mineralization also decreases because of unfavorablesoil conditions. Thus, retardation occurs in the nutrientcycle 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 herbaceouscover and forest floor on the skid road. Additionally, soilproperties have also changed to a great extent. It is obviousthat particularly the changes which occur subject to the soilcompaction will cause negative impacts on the water andair economies of the soils on the skid roads. Prompt actionsshould be taken to prevent and minimize such negativeimpacts of the skid roads. Especially, the skid roads shouldnot be used for long periods without taking any actionsafter they are built. Making rehabilitation works [5,29,30]on the skid roads to retain soil properties which havedrastically degraded and which have undergone erosionsand, therefore lost their plant cover shall be very useful interms of protection of the ecosystem.

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