Evaluating Effects Of Vegetation Cover Types On Overland Flow Generation And Soil Erosion In Luot Mountain

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MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT

VIETNAM FORESTRY UNIVERSITY

STUDENT THESIS

EVALUATING EFFECTS OF VEGETATION COVER TYPES ON

OVERLAND FLOW GENERATION AND SOIL EROSION

IN LUOT MOUNTAIN

Major: Natural Resources Management (Advanced Curriculum)

Code: D850101

Faculty: Forest Resources and Environmental Management

Student: Chao Thi Yen Student ID: 1053020749

Class: K55 Natural Resources Management Course: 2010 - 2014

Advanced Education Program Developed in collaboration with

Colorado State University, USA

Supervisor: Dr. Bui Xuan Dung

Hanoi, November 2014

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ABSTRACT

We examined the effects of three vegetation types: Cinnamomum parthenoxylon

plantation, shrub and grass on overland flow and soil erosion. We established three plots in

the same catchment but different vegetation cover types to measure the surface runoff and

soil erosion after each storm event. The plots were labeled Plot 1 for Cinnamomum

parthenoxylon plantation, Plot 2 for shrubs and Plot 3 for grass. In Plot 1, the canopy cover

was 90%; ground surface was covered 80% by small Cinnamomum parthenoxylon trees

and litterfall. Ground surface in Plot 2 was covered by shrub and litterfall up to 90% and

40 - 80% was the surface cover of Plot 3 was grass. The rainfall, surface runoff and

sediment were collected after each storm event. The total of monitoring storm was 10

storm events with the rainfall from 3 mm to 202 mm. There was no clear difference of

surface runoff and sediment in Cinnamomum parthenoxylon plantation, shrub and grass

based on ANOVA test. The total amount of surface runoff in Cinnamomum parthenoxylon

plantation was 7 mm ranged from 0.01 mm to 5 mm. This amount of surface runoff in

shrub was 12 mm ranged from 0.03 mm to 7.3 mm and the total amount of surface runoff

in grass was 13 mm ranged from 0.01 to 7.0 mm. The total amount of eroded soil in

Cinnamomum parthenoxylon plantation was 36 g/

ranged from 1.1 g/

to 16.4 g/

, in shrub was 77 g/

ranged from 0.8 g/

to 30 g/

and 86 g/

ranged from

0.8 g/

to 26 g/

in grass. When surface runoff increased, the sediment from soil

erosion also increased. The surface runoff in storms that bigger than 25 mm was 95 times

higher than that in storms less than 25 mm; the amount of eroded soil in storms that bigger

than 25 mm was 16 times greater than that in storms less than 25 mm.

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LIST OF TABLE CONTENTS

I. INTRODUCTION .............................................................................................. 1

II. OBJECTIVES................................................................................................... 6

2.1. Hypothesis ..................................................................................................... 6

2.2. Objectives...................................................................................................... 6

III. STUDY SITE AND METHODS ........................................................................ 7

3.1. Study site ...................................................................................................... 7

3.2. Methods......................................................................................................... 8

IV. RESULTS..................................................................................................... 13

4.1. Rainfall characteristics on Luot Mountain. ........................................................ 13

4.2. Surface runoff from Cinnamomum parthenoxylon plantation, grass and shrub......... 13

4.3. Sediment from Cinnamomum parthenoxylon plantation, grass and shrub................ 17

4.4. Relationship between sediment and surface runoff.............................................. 20

4.5. Amount of surface runoff and sediment from big storms compared to small storms. 21

V. DISSCUSION ................................................................................................ 24

5.1. Vegetation cover and surface runoff relationship. ............................................... 24

5.2. Vegetation cover and sediment. ....................................................................... 26

5.3. Sediment and surface runoff relationship........................................................... 28

5.4. Effect of storm sizes on surface runoff and soil erosion. ...................................... 29

VI. CONCLUSION ............................................................................................. 30

VII. REFERENCES............................................................................................. 31

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LIST OF FIGURES

Figure 1. (a) Location and topography of study site. (b) detail of study site and sample

plots. (c) plot 1. (d) plot 2. (e) plot 3. ........................................................................ 7

Figure 2. (a) Plot 2. (b) Plot 1 .................................................................................. 9

Figure 3. (a) Weighing soil samples. (b) Soil drying ................................................. 10

Figure 4.1. Rainfall characteristic measured at the VFU Luot Mountain weather station. 13

Figure 4.3. Surface runoff from Cinnamomum parthenoxylon plantation, grass and shrubs.

......................................................................................................................... 16

Figure 4.4: The response of sediment in Cinnamomum parthenoxylon plantation, grass and

shrub cover to each storm. (a) precipitation, (b) sediment in each storm. ...................... 19

Figure 4.5. Sediment from Cinnamomum parthenoxylon plantation, grass and shrub. .... 19

Figure 4.6. The relationship between sediment and surface runoff in different vegetation

cover types: (a) in Cinnamomum parthenoxylon forest. (b) in shrub. (c) in grass. .......... 20

Figure 4.7. Amount of sediment, surface runoff, surface runoff coefficient from small

storms and big storms: (a) sediment, (b) surface runoff, (c) surface runoff coefficient. .. 22