UNIVERSITI PUTRA MALAYSIA EFFECTS OF LOGGING … › download › pdf › 43000332.pdfPetak-pet.ak...

25
UNIVERSITI PUTRA MALAYSIA EFFECTS OF LOGGING OPERATIONS ON SOIL PHYSICAL PROPERTIES AND SOIL EROSION IN A HILL DIPTEROCARP FOREST OF PENINSULAR MALAYSIA BAHARUDDIN KASRAN FH 1992 3 CORE Metadata, citation and similar papers at core.ac.uk Provided by Universiti Putra Malaysia Institutional Repository

Transcript of UNIVERSITI PUTRA MALAYSIA EFFECTS OF LOGGING … › download › pdf › 43000332.pdfPetak-pet.ak...

  •   

    UNIVERSITI PUTRA MALAYSIA

    EFFECTS OF LOGGING OPERATIONS ON SOIL PHYSICAL PROPERTIES

    AND SOIL EROSION IN A HILL DIPTEROCARP FOREST OF PENINSULAR MALAYSIA

    BAHARUDDIN KASRAN

    FH 1992 3

    CORE Metadata, citation and similar papers at core.ac.uk

    Provided by Universiti Putra Malaysia Institutional Repository

    https://core.ac.uk/display/43000332?utm_source=pdf&utm_medium=banner&utm_campaign=pdf-decoration-v1

  • EFFECTS OF LOGGING OPERATIONS ON SOIL PHYSICAL PROPERTIES

    AND SOIL EROSION IN A HILL DIPTEROCARP FOREST

    OF PENINSULAR MALAYSIA

    By

    BAHARUDDIN KASRAN

    Thesis Submitted in Fulfillment of the Requirements for the Degree of Master of Science in the

    Faculty of Agriculture, Universiti Pertanian Malaysia

    December 1992

  • ACKNOWLEDGMENTS

    I would l ike to express my most sincere and deepest

    gratitude t o my major superv�sor, Associate Professor Dr. Mohd

    Mokhtaruddin bin Abdul Hanan, Faculty o f Agr i c u lt u r e ,

    Universiti Pertanian Malaysia f o r h i s h e l p f u l advice,

    encouragement and constructlve criticisms throughout the study.

    Thanks are a l s o due to my co-supervisor , A s s o c iate

    Professor D r . Nik Huhamad Ha)ld, Faculty of Forestry,

    Universiti Pertanian Halaysla for his invaluable comments ,

    guidance and encouragement . Special thanks are due to Associate

    Professor Dr. Siti Zauyah Darus and her laboratory assistants

    for their help in porosity analysis.

    I would like to acknowledge the Forest Research Institute

    Malaysia (FRIM) for giving me the opportunity to undertake this

    study. My appreciation to Dr. Abdul Rahim Hj Nik, my project

    Leader and Mohd Zaki Mohd Isa at FRIM, for his valuable

    comments. I am indebted to my cOlleagues Zulkifli ¥usop and

    Saifuddin Sulaiman for their cooperation.

    I like to express my speclal thanks to the research staff

    and foresters o f the Hydrology Section and field staff of

    stesyen Kec il Jengka, FRIM, for their assistance in field data

    collection and laboratory analyse s . They are Rajendran, Mohd

  • Sahat , Ahmad Shahar, Ibrahim, Hashim, Mokhtar, Ranjer Md Nor,

    Ayoub, Alisbana, Mat Salleh, Mohd Adam and Ahmad Marhani .

    Last but not least, my deepest gratitude and love to my

    wife, Tuminah for her understanding, sacrifices and patience;

    and to my children, Baharina, Haizal and Hamiza for their love

    and patience without which t h i s project would not have

    completed.

    iii

  • TABLE OF CONTENTS Page

    ACKNOWLEDGMENTS 11

    LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vii

    LIST OF FIGURES . . . . . . . . . . . . . . . . : . . . . . . . . . . . . . . . . . . . . . . . . . ix

    LIST OF PLATES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x

    LIST OF ABBREVIATIONS . . . . . . . • • • . . . . . . . . . . . . • • . . . . . . . . . . . . x i

    ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xii

    ABSTRAK xv

    CHAPTER

    I INTRODUCTION 1

    II REVIEW OF LITERATURE 5

    Logging System in Malaysia 5

    Soil Erosion and Surface Runoff in a Tropical Forest 6

    Effects o f Logging on Surface Runoff and Soil Loss 11

    Effects of Logging on Surface Runoff . . . . . . 11

    Effects of Logglng on Soil Loss . . . . . . . . . . . 13

    Effects of Logglng on Soil Physical Properties . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

    I I I METHODOLOGY 20

    Experimental Site 20

    Location and Topography 20

    Geology, 5011 and Vegetation 20

  • IV

    Climate 24

    Establishment of Erosion Plots 28

    Data Collection 31

    Rainfall 31

    Surface Runoff and Soil Loss Measurement ... 32

    Infiltration Rate 32

    Soil Sampling and Analyses 34

    Soil Sampling 34

    Soil Physical Properties 3 5

    Statistical Analyses 36

    RESULTS AND DISCUSSION 38

    Rainfall 38

    Soil Physical Properties . . . . . . . . • • . . . . . . . . • • . . . 40

    Soil Texture 40

    Bulk Density . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

    Total Porosity 43

    Organic Matter 5 1

    Soil Water Characteristics 53

    Infiltration Rate 56

    Effects of logging on Surface Runoff and Soil Loss 59

    Surface Runoff 59

    Soil Loss 68

    v

  • v SUMMARY AND CONCLUSION 7 5

    summary . . . . . . . . . . . . . . . . . . . . . • . . . . . . • • • . • . . . . . . . 7 5

    Conclusion

    REFERENCES CITED

    VITA

    vi

    79

    81

    94

  • LIST OF TABLES

    Table

    1 Soil Erosion and Runoff from Various Land

    2

    3

    Uses in Sarawak, Malaysia

    Bulk Density, Rate and Classified

    So�l Strength, Infiltration Air Space of Surface Soil

    Physica l

    b y Types of Disturbance . . . . . . . . . . .

    Characteristics of Jengka

    Page

    10

    18

    Experimental Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3

    4

    5

    Climatic Conditions of the Study Area

    Annual Basin,

    Rainfall for March 1987 to

    Jengka Experimental February 1989 . . . . . . . . . • .

    6 Textural Compositl.on of Undisturbed Area, Skid Trails and Logging Roads of Jengka

    7

    8

    9

    Experimental Basin

    M.ean Area, Jengka

    Soil Bulk Density of Undisturbed Skid Trails and Logging Roads of

    Mean Skid

    Experimental Basin

    Total Trails

    Porosl.ty of and Logging

    Experimental Basin

    Undisturbed Area, Roads of Jengka

    Mean Values of Total Number of Pores of Undisturbed Area, Skid Trails and Logging Roads of Jengka Experimental Basin . . . . . . . . . . .

    10 Total Porosity and Number of Pores in Each Plot at Different Slopes of Undisturbed

    11

    Area, Skid Trails and Logging Roads

    Organic Matter Content of Undisturbed Area, Skid Trails and Logging Roads of Jengka Experimental Basin . . . . . . . . . . . . . . . . . . . .

    12 Mean of Soil Mo�sture Characteristics of Three Different Slopes (10, 20 and 30%) of Disturbed and Undisturbed Areas at Different Pressures

    vii

    2 5

    38

    41

    42

    44

    46

    52

    53

    54

  • 13 Mean Available Water Capacity on Each Plot of Undisturbed and Disturbed S ites of Jengka Experimental Basin

    14 I n f iltration Rates on Each Plot o f Undisturbed and Disturbed Sites o f Jengka

    15

    16

    Experimental Basin

    Annual Rainfall, Surface Runoff and Rainfall-Runoff Coefficient from Undisturbed and Disturbed Sites of Jengka Experimental Basin . . . . . . . . . . . . . . . . . . . . . . . . . . .

    Annual Rainfall and Surface Runoff Characteristics of Undisturbed Forest in

    55

    57

    60

    Jengka Experimental Basin . . . . . . . . . . . . . . . . . . . 63

    17

    I.

    Annual Rainfall and surface Runoff Characteristics of Skid Trails in Jengka Experimental Basin

    Annual Rainfall Characteristics of Experimental Basin

    and Logging

    Surface Runoff Roads in Jengka

    64

    65

    19 Annual Soil Loss from Control and Treatment

    20

    21

    22

    Plots of Jengka Experimental Basin 6.

    Annual Soil Loss from undisturbed Forest on Different Slopes of Jengka Experimental Basin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72

    Annual Soil Loss from the on Different Slopes of Jengka Basin

    Annual Soil Loss from the

    Skid Trails Experimental

    Logging Roads on Different Slopes of Jengka Experimental

    73

    Basin . . . . . . . . . . .... . . . . . . . . . . . . . . . . . . . . . . . . . . 74

    viii

  • Figure

    1

    2

    3

    4

    5

    6

    7

    8

    LIST OF FIGURES

    Location of Study Site . . . . . . . . . . . . . . . . • • • • . . .

    Layout of Jengka Experimental Basin

    Mean Monthly Rainfall D istribution of Jengka Experimental Basin Based on Seven Years Data ( 1981 - 1987) . . . . . . . . . . . . . . . . . . . . .

    Mean Monthly of Some of Jengka Experimental Years Data (1981-198 7 )

    Climatic Parameters Basin Based on Seven

    Erosion Plots and Jengka Experimental

    I nstrument Layout at Basin

    Portable Rainfall Simulator to Measure Infiltration Rate

    Monthly Rainfall Two-Year Study to February 1989

    Soil Pore Size Undisturbed Forest

    Distribution During Period from March

    Distribution for

    the 1987

    the

    9 Soil Pore Size Distribution for the Skid

    10

    11

    12

    Trail

    Soil Pore Logging Road

    Size Distribution for the

    Monthly Rainfall-Runoff

    Variation of the Study Plots coefficient

    Monthly Soil Skid Trail

    Loss from Undisturbed Forest, and Logging Road of Jengka

    Experimental Basin

    ix

    Page

    21

    22

    26

    2 7

    30

    33

    39

    48

    49

    50

    66

    71

  • Plate

    1

    2

    3

    LIST OF PLATES

    Extraction of Log on the Skid Trail

    Using Crawler Tractor

    Winched Lorry or "San-Tai-Wong"

    Erosion Plot on the Logging Road

    Regeneration Logging Road

    of one

    Pioneer spec ies on Year After Logging

    K

    the

    Page

    7

    7

    29

    62

  • FAO

    IAHS

    IUFRO

    m . a . s . l .

    UNESCO

    USDA

    LIST OF ABBREVIATIONS

    Food and Agriculture Organization

    International Association of Hydrological Science

    International Union of Forestry Research Organization

    Meter above sea level

    United Nations Educational, Scientific and Cultural Organization

    United States Department of Agriculture

    xi

  • Abstract of thesis subm1.tted to the Senate of Universiti Pertanian Malaysia in fulfillment of the requirements for the degree of Maater of Science.

    EFFECXS OF LOGGING OPERATIONS ON SOIL PHYSICAL PROPERTIES

    AND SOIL EROSI ON IN A HILL DIPTEROCARP FOREST

    Chairman:

    Faculty :

    OF PENINSULAR MALAYSIA

    By

    BAHARUODIN KASRAN

    December 1992

    Associate Prof. Dr. Mohd Mokhtaruddin Abdul Hanan

    Agriculture

    The effects of 109g1-ng operations on soil phys ical

    properties and soil erOS10n 1n logged-over forest occurred

    mainly on severely disturbed s011, particu larly on the skid

    trail and logging road. ErOS10n plots were es tablished i n

    these areas to quantify the amount of surface runoff and soil

    loss. Soil samples from the upper layer of the skid trail,

    logging road and und1.sturbed area were analyzed for soi l

    physical properties.

    Significant chan ges 1n S011 physical properties w ere

    observed as a result of 10gg1.ng operations. The bulk density

    increased by 32 percent on the sk1d trail and 42 percent on the

    logging road, and the total porosity reduced by 62 and 69

    'H

  • percent, respectively. Logg1ng operat1ons not onl y reduced the

    total porosity but also changed the shape and Slze of pores.

    About 82 percent of the total poros1ty on undisturbed area

    consisted of elongated pores, 1 8 . 2 percent transmission pores

    and 1 1 . 4 percent f issures pores. On the skid trail, the total

    porosity consisted of 62 percent el ongated pores, 6.2 percent

    transmission and 4 . 9 percent f1ssures pores and on the logging

    road, the figures are 35, 6.4 and 2.6 percent, respectively.

    Thus the infiltration rate lS more ra p1d in undisturbed forest

    soil than in the skid trail and 10gg10g road because it is the

    elongated pores that play an important r o l e in water

    transmission. The higher the 1nf1ltrat1on rate the lower is the

    surface runo f f .

    The annual surface runoff from the logging road, skid

    trail and undisturbed forest were 2 0 . 3 , 1 4 . 5 and 2.3 percent of

    the total rainf all , respect1vely. The corresponding soil losses

    are 1 3 , 3 4 1 , 10,070 and 450 kg/ha/y, respectively. Ther efore a

    major proportion of the sed�ment Y1eld 1n logged-over forest

    originated from the l099�n9 roads and sk�d tra�lB. Severe

    erosion occurred du r1n g the f1rst year after logging and was

    less severe dur ing the second year. On the other hand the

    sediment yield from the und�sturbed areas was insignificant.

    Slope is one of the factors 1nfluencing soil erosion from

    the skid trails and 10gglng roads dur1ng the firs t year after

    X III

  • logging operations. The amount of SOll loss in the logged-over

    forest can be reduced l.f the grad l ent of the skid trails and

    logging roads does not exceed 20 percent.

    Erosion control measures should focused on controlling

    erosion from the 10gglng roads and skid trails. Control

    measures such as construct lon of cross drains on logging roads

    and skid trails must be done lmmedl.ate1y upon completion of

    logging operations. Another option for erosion control on

    logging roads and skl.d tralls lS to improve the surface

    condition of soil such as by SUb-solllng. Such practice will

    improve the infiltratlon characterl.stics of the soils and

    enhancing regeneration of vegetatl.on.

    nv

  • Abstrak tesis dikemukakan

    Pertanian Malaysia bagi memenuhi

    Ijazah Master Sains.

    ke·pada

    keperluan

    Senat

    untuk

    universiti

    memperolehi

    KESAK-KESAN OPERASl PEMBALAKAN KE ATAS SlFAT-SIFAT

    FIZlKAL DAN HAKISAN TANAH 01 HUTAH D1PTEROKAP

    8UK1T 01 seMENANJUNG MALAYSIA

    01eh

    BAHARUDDIN KASRAN

    Desember 1992

    Pengerusi Prof. Madya Dr. Mokhtaruddin Abdul Manan

    Fakulti Pertanian

    Kesan-kesan operasi pembalakan ke atas sifat-sifat fizikal

    tanah dan hakisan di hutan yang telah dibalak sering berlaku di

    tanah yang menga1ami kerosakan yang teruk, terutama di jalan

    tarik dan ja1an ba1ak. Petak-pet.ak hakisan dibina di kawasan

    ini bagi menentukan jum1ah air larian permukaan dan tanah

    terhakis. Contoh tanah di lap�san atas jalan tarik, jalan balak

    dan kawasan tidak diganggu telah dianalisa untuk menentukan

    sifat-sifat fizikal tanah.

    Operasi pembalakan menyebabkan berlakunya perubahan ke

    at as sifat-sifat fizikal tanah. Ketumpatan pukal bertambah 32

    peratus di jalan tarik dan 42 peratus di jalan balak.

    Sebaliknya jumlah keliangan masing-masing berkurangan kepada 62

    ,v

  • dan 69 peratus di jalan "tar1k dan jalan balak. Operasi

    pembalakan bukan sahaja mengurangkan jumlah keliangan bahkan

    juga mengubah bentuk dan saiz keliangan. Kira-kira 82 peratus

    dari jumlah keliangan di kawasan tidak diganggu terdiri

    daripada liang memanjang, 18.2 peratus liang penghantaran dan

    11.4 peratus liang rekahan. 01 Jalan tarik pula, 62 peratu$

    jumlah keliangan terdiri daripada liang memanjang, 6 . 2 peratus

    liang penghantaran dan 4.9 peratus liang rekahan. Oi jalan

    balak angka-angka tersebut ialah 35, 6 . 4 dan 2.6 peratus. Oleh

    itu proses penyusupan mudah bel"laku d1 hutan tidak diganggu

    berbanding di jalan tarik dan jalan balak. Ini disebabkan oleh

    liang memanjang memainkan peranan penting bagi pergerakan air

    dalam tanah. Semakin tinggi kadar penyusupan semakin rendah air

    larian permukaan.

    Air larian permukaan tahunan di jalan balak, jalan tarik

    dan hutan tidak diganggu masing-masing 2 0 . 3 , 14.5 dan 2 . 3

    peratus dari jumlah hujan" In1 bersamaan dengan kehilangan

    tanah masing-masing sebanyak 13, 3 4 1 , 10,070 dan 450

    kg/ha/tahun. Oleh itu sebahagian besar hasil kelodak dari hutan

    telah dibalak beraeal dari jalan balak dan jalan tarik. Hakisan

    yang teruk terjadi pada tahun pertama selepas pembalakan dan

    berkurangan pada tahun ber ikutnya. Sementara kawasan tidak

    diganggu menyumbangkan sedik1t sahaja hasil kelodak.

    xvi

  • Kecerunan merupakan satu daripada faktor-faktor yang

    mempengaruhi hakisan tanah dari j'alan tarik dan jalan balak

    terutama pada tahun pertama se lepas pembalakan. Jumlah tanah

    terhakis dari kawasan ini boleh dikurangkan jika kecerunan

    jalan tarik dan jalan balak tidak melebihi 20 peratus.

    Langkah-langkah mencegah hakisan harus diutamakan untuk

    mengawal hakisan di jalan balak dan jalan tarik. Langkah-

    langkah tersebut seperti pembinaan parit melintang di jalan

    balak dan jalan tarik harus dilaksanakan serta-merta setelah

    operaei pembalakan tamat. Satu lagi cara bagi mengawal hakisan

    di kawasan ini ialah memperbaiki keadaan tanah seperti

    mengemburkan permukaan tanah di kawasan-kawasan tereebut.

    Amalan ini akan meningkatkan Kadar penyusupan dan

    mempercepatkan pertumbuhan tumbuh-tumbuhan.

    XVlJ.

  • CHAPTER I

    INTRODUCTION

    During the past two decades more than 1 . 5 million hectares

    of lowland tropical forests in Peninsular Malaysia have been

    converted to agricultural land mainly for the planting of

    rubber, oil palm and cocoa. This has resulted in a massive

    reduction of forested land in the country. I n 1955 forest

    constituted about 7 5 percent of the total land area in

    Peninsular Malaysia. This was further reduced to 55 percent in

    1970, 50 percent in 1980 ( Chong, 1985) and 47 . 7 percent in 1990

    (Malaysia, Ministry of primary Industries, 1991) . Most of the

    forested land in Malaysia today are confined to hilly areas and

    steep terrains and the lowland dipterocarp forests have almost

    been totally replaced by agricultural crops.

    Logging activities in the steepland areas have created a

    number of serious environmental and ecological problems. The

    most obvious are those pertaining t o the hydrology of

    downstream areas, such as deterioration in water quality,

    increased soil erosion, river sedimentation and silting of

    reservoirs. In Malaysia, the effects of timber harvesting on

    soil erosion and sedimentation have been reported by a number

    of investigators including Burgess ( 1971 ) , Baillie ( 1972 ) , Liew

    (1974) , Jones ( 1976 ) , Salleh et al . , (1981a, 1981b ) , Lai and

    1

  • 2

    Shams uddin ( 1 985 ) , Lai and Rentap (1986 ) and Baharuddin

    ( 1988a ) .

    Most of these studies were based on experimental

    watersheds. The common approach is to estimate erosion by

    determining sediment content of stream water from the

    watershed. It provides the general idea of the treatment effect

    on sediment production, which is attributed mainly to surface

    erosion ( sheet, rill and gully) , stream bank and streambed

    erosion. The general conclusion of these studies is that

    logging activities contributed a significant amount of

    sediments in the stream water. Nevertheless, the exact source

    o f sediments s t i l l remains unknown. I t is imperative to

    indicate the exact location and sediment regime in the area so

    that systematic erosion control measures could be implemented

    to minimize sediment content in the streams.

    I n addition to sedimentation, forest harvesting operations

    are definitely one of the factors that changed the soil

    physical properties and aesthetic values of the landscape.

    Logging road construction, usage of heavy maChinery and

    transportation during logging operations tend to mOdify the

    physical properties of the upper layer of forest soil which may

    significantly affect regeneration growth. The impact of logging

    operations on soil physical properties in temperate region is

    well documented ( Froehlich 1972 ) . However , in Malaysia, such

    study has not been reported, except by Kamaruzaman ( 1987 ) . The

  • 3

    alteration of soil physical properties due to timber harvesting

    i s c l os e l y associated with s o i l l o s s o f the a r e a . This

    relationship characteristics and the soil loss variation should

    be studied in order to gain a better understanding of the soil

    erosion problem.

    This thesis reports a study of the relationship between

    timber harvesting, soil erosion and Boil physical properties in

    a logged-over forest in Peninsular Ma lays i a . The general

    objective is to determine the amount of surface runoff and

    soil loss and to assess the changes in soil physical properties

    resulting from construction of logging road and skid trails in

    logged-over forest of Peninsular Malaysi a . The spec i f i c

    objectives are to:

    1 . quantify the amount of

    loss from logging roads,

    undisturbed forest, and

    surface runoff and soil

    skid t r a i l s and

    2. describe some selected soil properties such as bulk

    density, porosity, soil organic matter, soil water

    characteristics and infiltration rate on the logging

    road, skid trail and undisturbed forest.

    The study was conducted in a logged-over forest at Tekam

    Forest Reserve, Pahang, Peninsular Malaysia. Nine erosion plots

    were established on three different sites, namely undisturbed

    forest, skid trails and logging roads. At each site, plots were

  • 4

    established on three different slope categories ( 10 , 20 and 30

    percent ) . The study commenced six months after logging

    operation was completed and continued for a period of two

    years, that is, from March 1987 to February 1989.

  • CHAPTER II

    REVIEW OF LITERATURE

    Logging system in Malaysia

    Selective logging method was introduced in Malaysia as a

    forest management system since 1948 . It was then known as the

    Halayan Uniform System (MUS) (Wyatt-Smith, 1963). A new system

    known as the Selective Management System (SHS) was implemented

    in 1970 to replace HUS because the HUS system was found to be

    unsuitable to be practiced in the hill forest areas ( Thang,

    1986) . This new system was designed to optimize the management

    objectives of an economic and efficient harvesting, forest

    sustainability and minimum forest development cost. In this

    system, minimum cutting limits are 45 and 50 cm diameter breast

    height for the non-dipterocarp

    respectively.

    and dipterocarp species.

    The logging system which has been developed in the forests

    of Halaysia are completely mechanized and requires low capital

    (FAO, 1970, 1973; Ellis, 1976; Jones, 1976). The basic logging

    operations include tree felling, construction of forest road

    and log transportation. During road construction, the topsoil

    and forest debris are pushed aside to ensure firm and level

    footing for the skidding operation. The activities during this

    operation and the usage of heavy earth-moving equipment such

    5

  • 6

    as tractors and skidders cause severe soil degradation. In

    log transportation, the crawler tractor is used for skidding or

    hauling the logs from the felling site to temporary landing

    (Plate 1 ) . The logs that are skidded are usually largei 50 to

    100 em in diameter at breast height, cut into logs of about 5

    to 7 m long or sometimes at tree length. Under such practice,

    only heavy equipment are used. The main vehicle tranporting

    logs to the logyard is a winch lorry locally known as " San-Tai-

    Wong" ( Plate 2 ) . These skidding and transportation activities

    can cause serious degradation of soil physical properties both

    during the dry and wet seasons. 50il degradation and compaction

    resulting from logging will certainly induce surface runoff and

    erosion.

    soil Erosion and Surface Runoff in a

    Tropical Forest

    In the temperate zone , surface erosion in undisturbed

    forest is minimal (Megahan and King, 1975) . This is not true

    for the tropical forest because soil erosion can be detected

    even under natural forest (Leigh, 1 9 7 8 ; Fearnside, 1979;

    Putj aroon and Pongboon, 1987 ) . Putjaroon and Pongboon ( 19 8 7 )

    found that the amount o f runoff and soil loss i n a dry

    dipterocarp forest in Saho1nakron Province of Thailand were

    1 , 529 m3/ha/y and 664 kg/ha/y, respectively . The values are

    however much lower when compared to that of abandoned fields

  • Plate 1. Extraction of Log Using Crawler

    Tractor on the Skid Trail.

    Plate 2. Winched Lorry or "San-Tai-Wong".

    7