Soil erosion and overland flow response to clear cutting of acacia hybrid plantation in headwater catchment of hoa binh province

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM NATIONAL UNIVERSITY OF FORESTRY STUDENT THESIS SOIL EROSION AND OVERLAND FLOW RESPONSE TO CLEAR CUTTING OF ACACIA HYBRID PLANTATION IN HEADWATER CATCHMENT OF HOA BINH PROVINCE Major: Natural Resources Management Faculty: Forest Resource and Environmental Management Student: Nguyen Van Cong Student ID: 1553090035 Class: K60 – Natural Resources Management Course: 2015 – 2019 Advanced Education Program Developed in collaboration with Colorado State University, USA Supervisor: Assoc Prof Bui Xuan Dung Ha Noi, 2019 ACKNOWLEDGEMENT First and foremost, to be able to conduct this research, we would like to express our sincere respect to our supervisor - Assoc Prof Dr Bui Xuan Dung for his enthusiastic and patient support with invaluable comments In addition, we appreciated the support of other lectures during the time we analyzed the data Not only that, many thanks are due to our friends when we started to collect and analyze data They always give our team the support whenever we needed In terms of difficulties, the transport to study sites was hard without our companions Lastly, I express my gratitude to local people who own the Acacia plantation model for allowing us to conduct this research in this site They also informed us about the weather which extremely support us to get the data i CONTENTS ACKNOWLEDGEMENT i LIST OF FIGURES iv LIST OF TABLES v ABBREVIATIONS vi ABSTRACT vii CHAPTER I INTRODUCTION CHAPTER II GOAL AND OBJECTIVES 2.1 Goal 2.2 Objectives CHAPTER III STUDY SITE AND METHODS 3.1 Study Site 3.2 Methods 3.2.1 Legacy data 3.2.2 Installing monitoring plot 3.2.3 Survey time 3.2.4 Rainfall and soil physical characteristics measurement 10 3.2.5 Runoff and Soil erosion measurement 12 3.2.6 Vegetation observation measurement 14 3.2.7 Topographic survey: Slope, coordinate system and altitude of four plots are measured by using GPS and compass 14 3.2.8 Data Analysis: Data was processed by using Microsoft excel and SPSS 15 CHAPTER IV 16 RESULTS AND DICUSSION 16 4.1 Soil physical factors and vegetation on study sites 16 4.2 Precipitation characteristics 16 4.3 Response of surface runoff to clear cutting Acacia plantation 18 4.4 Response of soil erosion to clear cutting Acacia plantation 22 ii V CONCLUSIONS, LIMITATION AND RECOMMENDATION 26 5.1 Conclusions 26 5.2 Limitation 26 5.3 Recommendation 26 REFERENCES iii LIST OF FIGURES Figure The map of study site: Figure Establishing plot model Figure 3 Location of plots Figure Harvesting Acacia process Figure Two plots before cutting Figure Two plots after cutting Figure Rain gauge site 10 Figure Porosity measurement process 11 Figure Surface runoff measurement process 12 Figure 10 Soil erosion measurement process 13 Figure 13 Excel and SPSS software 15 Figure Storm events 17 Figure Precipitation, surface runoff at plots before and after cutting 18 Figure Precipitation, runoff coefficient at plots before and after cuttin 19 Figure 4 Precipitation accumulation, runoff accumulation at plots before and after cutting 20 Figure Correlation of surface runoff between plots before and after cutting 21 Figure Precipitation, soil erosion at plots before and after cutting 22 Figure Precipitation accumulation, soil erosion at plots before and after cutting 23 Figure Correlation of soil erosion between plots before and after cutting 24 iv LIST OF TABLES Table Observation plots characteristic at the study site 16 Table Precipitation, API7 and rainfall intensity on study sites after cutting 17 Table Surface runoff, runoff coefficient analysis between plots before and after cutting 19 Table 4 Independent samples t-test for the response of surface runoff to clear cutting 20 Table Soil erosion analysis between plots before and after cutting 22 Table Independent samples t-test for the response of soil erosion to clear cutting 23 Table TCVN 5299: 2009 - Method for determination of soil erosion by rainfall 24 v ABBREVIATIONS API7 Antecedent precipitation index for days Cm3 Cubic centimeter g gram mm millimeter hr hour df Degree of freedom GPS Global position system Hectare P-value Probability R2 Coefficient of determination RUSLE Revised Universal Soil Loss Equation SPSS Statistical Package for the Social Sciences USA United States of America Std Deviation Standard Deviation TCVN Vietnam standard vi ABSTRACT To assess the response of surface runoff generation and soil erosion to clear cutting of Acacia plantation in headwater catchment of Hoa Binh province, plots (15 m2/plot) of Acacia plantation 5- year- old were set up and monitored in periods from 22 April,2018 to 12 May, 2019 (before cutting and after cutting) with 70 storm events in Truong Son commune, Luong Son district, Hoa Binh province The main finding included: Surface runoff and runoff coefficient in plot (0.26 mm/15m2/storm and 0.56%/15m2/storm) were higher than plot 1(0.1 mm/15m2/storm and 0.23%/15m2/storm) after cutting Besides, after cutting, the amount of soil erosion in plot (309.27 g/15m2/storm) was also higher than plot (240.37 g/15m2/storm) The correlation of surface runoff and soil erosion between plots had strong relation after cutting (p