towards sustainability of land use in a highly vulnerable and degraded

Bui Le Vinh Towards sustainability of land use in a highly vulnerable and degraded tropical soil landscape of northern Vietnam – bridging scales Auf dem Weg zu einer nachhaltigen Landnutzung in einer sehr anfälligen und degradierten tropischen Bodenlandschaft des nördlichen Vietnam – Skalen Überbrückung Hướng tới sự bền vững trong sử dụng đất cho vùng đất bị thoái hóa và dễ bị tổn thương ở vùng đồi núi phía bắc Việt Nam – Mô hình mở rộng This thesis was accepted as a doctoral dissertation on December 17th, 2014 in fulfilment of the requirements for the degree “Doktor der Agrarwissenschaften” by the Faculty of Agricultural Sciences at Hohenheim University. Date of oral examination: March 24th, 2015 Examination Committee: Head of the Committee: Prof. Dr. Jens Wünsche Supervisor and Review: Prof. Dr. Karl Stahr CoReviewer: Prof. Dr. Joachim Müller Additional examiner: PD Dr. rer. nat. Daniela Sauer

Towards sustainability of land use in a highly vulnerable and degraded tropical soil landscape of northern Vietnam - bridging scales PhD dissertation, 2015, Bui Le Vinh INSTITUTE OF SOIL SCIENCE AND LAND EVALUATION UNIVERSITY OF HOHENHEIM Soil Science and Petrography Unit Prof. Dr. Karl Stahr Towards sustainability of land use in a highly vulnerable and degraded tropical soil landscape of northern Vietnam – bridging scales Dissertation Submitted in fulfillment of the requirements for the degree "Doktor der Agrarwissenschaften" (Dr.sc.agr. in Agricultural Sciences) to the Faculty of Agricultural Sciences presented by M.Sc. agr. Bui Le Vinh Hai Duong, Vietnam 2015 HOHENHEIMER BODENKUNDLICHE HEFTE - NR. 116 Bui Le Vinh Towards sustainability of land use in a highly vulnerable and degraded tropical soil landscape of northern Vietnam – bridging scales Auf dem Weg zu einer nachhaltigen Landnutzung in einer sehr anfälligen und degradierten tropischen Bodenlandschaft des nördlichen Vietnam – Skalen Überbrückung Hướng tới bền vững sử dụng đất cho vùng đất bị thoái hóa dễ bị tổn thương vùng đồi núi phía bắc Việt Nam – Mô hình mở rộng This thesis was accepted as a doctoral dissertation on December 17th, 2014 in fulfilment of the requirements for the degree “Doktor der Agrarwissenschaften” by the Faculty of Agricultural Sciences at Hohenheim University. Date of oral examination: March 24th, 2015 Examination Committee: Head of the Committee: Prof. Dr. Jens Wünsche Supervisor and Review: Prof. Dr. Karl Stahr Co-Reviewer: Prof. Dr. Joachim Müller Additional examiner: PD Dr. rer. nat. Daniela Sauer Table of Contents i 1. Introduction . 1.1. Problem setting . 1.2. Objectives 1.3. Hypotheses . 2. Methodology 2.1. SOTER approach 2.2. Geographic Information System . 2.3. Data collection and derivation . 2.3.1. Secondary data . 2.3.2. Primary data . 10 2.3.3. Derivation of some terrain variables using GIS techniques 14 2.3.3.1. Generation of main slope positions . 14 2.3.3.2. Generation of curvatures 16 2.3.3.3. Generation of slope forms based on the main slope positions . 17 2.3.4. Soil property calculation for Yen Chau . 20 2.3.4.1. Calculation of further physical properties 20 2.3.4.2. Calculation of further chemical properties 21 2.3.4.3. Criteria for soil quality analysis . 22 2.4. Soil mapping under fuzzy logic and Soil-Land Inference Model (SoLIM) . 23 2.4.1. Limitations of conventional soil mapping under crisp logic and introduction of fuzzy logic soil mapping 23 2.4.2. Theoretical basis for soil inference using fuzzy logic . 26 2.4.2.1. Basic theory . 26 2.4.2.2. Expert system approach . 27 2.4.2.3. Fuzzy set theory . 28 2.4.3. Methodology 29 2.4.3.1. Knowledge acquisition 29 2.4.3.2. Soil-environment key development interview . 30 2.4.3.3. Soil-environment description interview . 31 2.4.3.4. Optimality curve definition interview 32 2.4.3.5. Knowledge verification interview . 33 2.4.3.6. The fuzzy soil inference process 33 3. General description of the study area . 35 3.1. Physiography . 35 3.2. Geology 37 3.3. Climate . 42 ii Table of Contents 3.4. Soils and Land use 44 3.5. Ethnic groups and land use systems . 46 4. Results 49 4.1. Characterization of the SOTER database of Yen Chau district 49 4.1.1. Terrain units 49 4.1.1.1. Characterization of major landforms and terrain units 49 4.1.1.2. Determination of terrain units for each of the parent materials . 51 4.1.2. Terrain components . 58 4.1.3 Soil components 60 4.2. Soils and soil properties . 66 4.2.1. Overview of soils of Yen Chau . 66 4.2.2. Major soil properties for soil quality assessment 74 4.2.2.1. Air capacity – AC (%) . 75 4.2.2.2. Available water capacity – AWC (l/m2) 75 4.2.2.3. Organic matter – OM (kg/m2) . 78 4.2.2.4. Total nitrogen – Nt (kg/m2) 78 4.2.2.5. Available phosphorous – PBray1 (g/m2) 79 4.2.2.6. S-value . 80 4.2.2.7. The sum parameter N-P-S . 80 4.2.2.8. Biological activity 82 4.2.2.9. Human impact 83 4.2.3. Computations of correlation coefficients for soil properties . 84 4.2.4. Major soils and their distribution in Yen Chau . 93 4.3. Soil mapping model 109 4.3.1. Calibration of the formation of soils in Yen Chau 109 4.3.2. Spatial delineation of the soil map of Yen Chau using SoLIM software 109 4.4. Soil quality mapping model . 117 5. Discussion . 127 5.1. The Yen Chau SOTER database . 127 5.2. The variability of Yen Chau soils 128 5.2.1. Soil pH (H2O) 129 5.2.2. The A-horizon thickness . 130 5.2.3. Soil organic matter 130 5.2.4. Total nitrogen - Nt . 132 5.2.5. Base saturation 134 5.2.6. Cation exchange capacity for clay minerals (CECclay) 136 5.2.7. S-value . 138 Table of Contents iii 5.2.8. Standardized parameter N-P-K 139 5.2.9. Soil forming processes to the variability of soils in Yen Chau . 140 5.2.9.1. Clay illuviation 140 5.2.9.2. Clay formation . 142 5.2.9.3. Humus accumulation . 143 5.2.9.4. Decalcification . 144 5.2.9.5. Base leaching . 145 5.2.10. Environmental conditions and their role in soil and soil quality mapping 147 5.2.10.1. Climate in association with elevation . 147 5.2.10.2. Parent material 149 5.2.10.3. Relief 151 5.2.10.4. Vegetation 154 5.2.10.5. Biological activity 155 5.2.10.6. Human impact 155 5.2.10.7. Time . 156 5.3. Validation of the soil and soil quality maps 158 5.3.1. Validation of the soil map . 159 5.3.2. Validation of the soil quality map . 159 6. Conclusions 163 6.1. General conclusions 163 6.2. Specific conclusions . 163 7. Summaries . 165 7.1. Summary 165 7.2. Zusammenfassung 168 7.3. Tóm tắt . 171 8. References 175 8.1. Literature . 175 8.2. Other information sources . 188 9. Appendix 191 9.1. Abbreviations 191 9.2. Description of reference soil profiles 192 9.3. Soil properties calculations for the Yen Chau SOTER database . 217 Acknowledgement . 223 iv Table of Contents Introduction 1. Introduction Northwestern Vietnam is a mountainous region and home to almost three million people from many different ethnic minorities. The region has remained the poorest over the whole country for many years with the highest poverty rate (Phan, 2008). The region has a wide range of elevations, strong relief variations, land use patterns, climatic patterns, land cover, and petrography. The geological patterns of the area are ophiolite complex, granitic intrusion complexes, volcanic rocks, terrigenous and carbonate sedimentary rocks ranging from Proterozoic age till today (Hung, 2010b). Swiddening and slash-and-burn agriculture had a long cultivation history of people in mountainous regions and they had been claimed to be sustainable (Dao, 2000). These cultivation practices worked very well in providing efficient subsistence to local people and sustaining the land use systems of the area (Vien et al., 2004). However, due to population growth and immigration happening over decades, like many other mountainous regions, the population in the northwest of Vietnam has risen remarkably, creating a severe stress on cultivated soils in covering the food demand for the growingpopulation. Moreover, upland agriculture has been shifted towards meeting markets’ demands, or market-orientation, i.e. intensification of cash crops like maize as a leading income crop (Clemens et al., 2010). This has promoted more intensive uses of soils and deforestation to widen arable land on hill slopes. Consequences have then quickly arrived represented by serious flooding due to increasing deforested area, increasing soil degradation due to soil erosion and soil nutrient depletion because of overuse of agro-chemicals and intensive use of agricultural land, and, therefore, decreasing productivity of the cultivated soils (Toan et al., 2001, Wezel et al. 2002). The demand to mitigate these facts is to drive cultivation practices towards sustainability. Some solutions to achieving the sustainable development goal are to recover the lost forested area and importantly to adapt new suitable crops that not only bring high income to the local people but also function to mitigate soil degradation and recover soil quality. To so, a good knowledge of soil resources and soil quality must be necessarily achieved (Igué, 2000). 1.1. Problem setting A common database about different soils, their properties and distribution for the whole country has not been completed. Soil information achieved so far is very sparse. And not an exception, the northwest of Vietnam does not have a good soil database necessary for related research or applications (Bo et al., 2002; Tin, 2005). The ministry of Natural Resources and Environment (Circular 28th, 2010) of Vietnam defined a set of technical and economic requirements for land surveys, soil mapping and evaluation of soil quality. For soil mapping, soil sampling in mountainous regions is carried out within a minimum areal unit of 30 with soil profiles studied, about profile for on average. Physical properties are described for all profiles and only of them is sampled for chemical analyses. Therefore, there maximum different soils can be classified for an area of 30 ha. Introduction With soil profiles studied for one catena, Clemens et al. (2010) found soil types that likely have been formed by different distinctive combinations of slope position, slope inclination, elevation, and period of cultivation. According to our soil survey experience, an average catena has an area of 3-10 ha. Thus, with an area of 30 we can have at least three adjacent catenas which could end up with having more than soil types found when applying the method of Clemens et al. (2010). Therefore, the sampling method of the Circular 28th potentially will produce a huge overgeneralization of soil information. It means a lot of soil information in a huge area will be lost, if this method is applied. Therefore, it is necessary to have another soil mapping approach that can better achieve soil knowledge for a mountainous region of Vietnam. Modern soil mapping methods have focused on studying relationships between soils and their forming factors (Odeh et al., 1991; Zhu et al., 1996, 1997a; Batjes et al., 1997, 2000, 2008; Schuler et al., 2008; Qin et al., 2009, 2012). Jenny (1941) mentioned five main soil-forming factors: parent material, climate, organisms, topography, and time. In a study about the development of soils on hill slopes in a South Australian subcatchment related to the environment, Odeh et al. (1991) emphasized the importance of soil-landform interactions in the local pedogenesis. They concluded that landform features such as slope gradient, plan convexity, profile convexity contribute remarkably to spatial variations of soils. The combinations of profile-plan curvatures result in different slope forms (surface forms) which will be discussed in details in section 2.3.3. Slope forms were taken into account in studying soil variations at large scales (subcatchment scale to regional scale) in some other studies (Schuler et al., 2008; Qin et al., 2009, 2012; Cong, 2011). Qin et al. (2009) developed an eleven slope position system for an area of 60 km2 with low relief energy (average slope gradient of 20, elevation difference between the lowest and highest points of 120 m). Cong (2011) and Schuler et al. (2008) also considered slope forms in mapping soils at subcatchment and catchment scales in mountainous areas having much stronger relief conditions. However, they simply described some major slope forms, for example straight-straight, convex-convex, concave-concave, etc., that were observed in their soil observations, rather than trying to capture an overall image of slope forms for the whole areas. Therefore, this information might not be sufficient in drawing a good picture of soil-landscape relationships. Especially when soils of a larger area (ex. 1:25.000 or smaller scale) having strong relief conditions are to be mapped from catena units. 1.2. Objectives In the last years, several studies were made within the SFB 564 (Sonderforschungsberich 564) Programme (or the Uplands Program) in Vietnam on soil quality (Clemens et al., 2010; Häring et al., 2010), land evaluation (Cong, 2011) in northwestern Vietnam. Clemens et al. (2010) and Häring et al. (2010) studied soil quality at catchment scale. Cong (2011) implemented a land evaluation research at two small catchments. Starting from a sketch, he developed a Soils and Introduction Terrrain Digital Database (SOTER) for the catchments as the basis for the implementation of his land evaluation work. The overall goal of this study over the last years was to develop a detailed soil information system for the northwestern mountainous district of Yen Chau using SOTER database upscaled from Cong’s work (2011). From this upscaled SOTER database, a soil map and a soil quality map will be generated for Yen Chau district using Soil and Landscape Index Model (SoLIM). To achieve this goal, the following objectives have been identified:     Derivation of a detailed slope form system for the area. The result will be a map consisting of all possible slope forms that will be used later as one of the soil-forming environmental parameters in the SoLIM model in mapping the variations of different soils and the quality of these soils. Development of a SOTER database for Yen Chau district that rules the formation of soils through unique combinations between soils and environmental conditions such as landforms, slope forms, slope gradients, parent materials. Application of SoLIM in deriving the soil map for Yen Chau based on the relationships between soils and terrain characteristics from the SOTER database. Calculation of soil quality indices and studying their relationship with the environmental parameters for the development of a soil quality map for Yen Chau applying SoLIM. 1.3. Hypotheses In the efforts to the mapping of soils and their quality in Yen Chau district, the following main hypotheses need to be proven. a) Different rock types have certain influence on soil occurrences and soil quality. b) Slope inclination affects the degree of soil loss due to erosion, therefore, the soil quality, and leads to transformations to new soils in relation to human impacts through agricultural activities. c) Elevation plays an important role in the occurrences of different soils and their quality degrees. d) Slope forms are very important in capturing spatial variations of soils and if they are correctly spatially delineated, loss of soil information can be minimized and spatial soil gradation can be better seen as a continuum. e) The age of cultivation in relation to the major slope positions (crest, upper-, middle-, foot slope, and valley) has influences on soil distribution and soil quality. 208 Appendix 17. Profile VI/YC/C.On6: Classification: Hydragric Escalic Anthrosol (Clayic) Date of description: 12.11.2010 Location: Tram Hoc village, Chieng On commune, Yen Chau district, Son La province Longitude: 0414925 Latitude: 2320272 Altitude: 906m Parent rock: volcanic rock (VO2) Slope inclination: approximately 00 Slope aspect: Slope position: valley Slope form: Land-use: paddy rice Profile description: Horizon Depth (cm) Description Ah 0–57 Brown (7.5 YR 4/5); clay texture; soil material added from neighbouring leveled hills years before the investigation; granular structure in the first 10 cm and subangular blocky structure lower; rock fragments are abundant and medium gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; no presence of CaCO3; very fine and fine roots are commonly seen; gradual boundary to CBt1. Ahb 57–90 Dark colour (5 YR 3.5/1); clay texture; rock fragments are few, fine gravel and rounded, fresh or slightly weathered; extremely calcareous; friable moist; sticky and plastic; very fine and fine roots from previous seasons. Appendix 209 18. Profile VI/YC/C.On7: Classification: Cutanic Haplic Alisol (Siltic Chromic) Date of description: 13.11.2010 Location: Tram Hoc village, Chieng On commune, Yen Chau district, Son La province Longitude: 0414796 Latitude: 2320111 Altitude: 945m Parent rock: volcanic rock (VO2) Slope inclination: approximately 260 Slope aspect: 600 Slope position: upper foot slope Slope form: Straight-Concave (SC) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–25 Dull yellowish brown (10 YR 4.5/3); clay loam texture; very fine to fine granular structure; rock fragments are many and mostly fine and medium gravel and angular, weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; abrupt boundary to AhBt. AhBt 25–75 Greyish brown (7.5 YR 5/2); clay loam texture; rock fragments are dominant, boulders and large boulders, weathered; friable moist; slightly sticky and slightly plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; common and faint coatings, humus and clay coatings; no roots; abrupt boundary to CBt. BtC 75–160 Bright yellowish brown (10 YR 5.5/6); clay texture; rock fragments are dominant, boulders and large boulders, weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; common and faint coatings, clay coatings; no roots. 210 Appendix 19. Profile VI/YC/C.On8: Classification: Haplic Alisol (Chromic) Date of description: 31.03.2011 Location: Na Cai village, Chieng On commune, Yen Chau district, Son La province Longitude: 0411238 Latitude: 2318312 Altitude: 960m Parent rock: Quartz-rich metamorphic (QA) Slope inclination: approximately 280 Slope aspect: 600 Slope position: upper slope Slope form: Straight-Straight (SS) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–20 Brownish black (7.5 YR 3.5/2); silty loam texture; very fine to fine granular structure; rock fragments are very few and mostly fine gravel and angular, fresh or slightly weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; clear boundary to AhBt. AhBt 20–60 Dark dull brown (7.5 YR 4.5/6); silty loam texture; subangular blocky structure; rock fragments are few and from fine to coarse gravel and angular, fresh or slightly weathered; friable moist; slightly sticky and slightly plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, humus and clay coatings; very fine and fine roots; gradual boundary to Bt. Bt 60–110 Dull brown (7.5 YR 5/6); clay loam texture; subangular blocky structure; rock fragments are few, fine to coarse gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, clay coatings; few very fine, fine and medium roots; diffuse boundary to BtC. CBt 110–130 Dull brown (7.5 YR 5/6); clay loam texture; subangular blocky structure; rock fragments are many, coarse gravel and stones, fresh or slightly weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; dominant and faint coatings, clay coatings; no roots. Appendix 211 20. Profile VI/YC/C.On9: Classification: Haplic Alisol (Chromic) Date of description: 01.04.2011 Location: Na Cai village, Chieng On commune, Yen Chau district, Son La province Longitude: 0411282 Latitude: 2318320 Altitude: 937m Parent rock: Quartz-rich metamorphic (QA) Slope inclination: approximately 300 Slope aspect: 700 Slope position: middle slope Slope form: Straight-Straight (SS) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–20 Brownish black (7.5 YR 4/2); silty loam texture; very fine to fine granular structure; rock fragments are very few and mostly fine gravel and angular, fresh or slightly weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; gradual boundary to AhBt. AhBt 20–70 Brown (7.5 YR 4/4); silty loam texture; subangular blocky structure; rock fragments are few and from fine to coarse gravel and angular, fresh or slightly weathered; friable moist; slightly sticky and slightly plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, humus and clay coatings; very fine and fine roots; diffuse boundary to Bt. Bt 70–110 Dull brown (7.5 YR 5/6); clay loam texture; subangular blocky structure; rock fragments are few, fine to coarse gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, clay coatings; few very fine, fine and medium roots; clear boundary to BtC. BtC 110–150 Dull brown (7.5 YR 5/7); silty clay loam texture; subangular blocky structure; rock fragments are many, coarse gravel and stones, fresh or slightly weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; dominant and faint coatings, clay coatings; no roots. 212 Appendix 21. Profile VI/YC/C.On10: Classification: Haplic Alisol (Chromic) Date of description: 02.04.2011 Location: Na Cai village, Chieng On commune, Yen Chau district, Son La province Longitude: 0411310 Latitude: 2318345 Altitude: 922m Parent rock: Quartz-rich metamorphic (QA) Slope inclination: approximately 140 Slope aspect: 900 Slope position: foot slope Slope form: Straight-Convex (SV) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–17 Brownish black (7.5 YR 4/2.5); clay loam texture; very fine to fine granular structure; rock fragments are few and mostly fine gravel and angular, fresh or slightly weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; clear boundary to AhBt. AhBt 17–50 Brown (7.5 YR 4/5); clay loam texture; subangular blocky structure; rock fragments are few and from fine to coarse gravel and angular, fresh or slightly weathered; friable moist; slightly sticky and slightly plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, humus and clay coatings; very fine and fine roots; gradual boundary to Bt. Bt 50–100 Dull brown (7.5 YR 5/6); clay texture; subangular blocky structure; rock fragments are few, fine to coarse gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, clay coatings; few very fine, fine and medium roots; diffuse boundary to BtC. CBt 100–140 Dull brown (7.5 YR 5/7); clay texture; subangular blocky structure; rock fragments are many, coarse gravel and stones, weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; dominant and faint coatings, clay coatings; no roots. Appendix 213 22. Profile VI/YC/C.On11: Classification: Haplic Alisols (Chromic) Date of description: 03.04.2011 Location: Na Cai village, Chieng On commune, Yen Chau district, Son La province Longitude: 0411382 Latitude: 2318439 Altitude: 930m Parent rock: Quartz-rich metamorphic (QA) Slope inclination: approximately 170 Slope aspect: 1900 Slope position: middle slope Slope form: Straight-Convex (SV) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–15 Brownish black (7.5 YR 4/2.5); clay loam texture; very fine to fine granular structure; rock fragments are few and mostly fine gravel and angular, fresh or slightly weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; clear boundary to Bt1. AhBt 15–50 Brown (7.5 YR 4/4); clay loam texture; subangular blocky structure; rock fragments are very few and from fine to coarse gravel and angular, fresh or slightly weathered; friable moist; slightly sticky and slightly plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, humus and clay coatings; very fine and fine roots; gradual boundary to Bt2. Bt1 50–100 Brown (7.5 YR 4/6); clay texture; subangular blocky structure; rock fragments are very few, fine to coarse gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, clay coatings; few very fine, fine and medium roots; diffuse boundary to Bt3. Bt2 100–150 Dull brown (7.5 YR 4.5/6); clay texture; subangular blocky structure; rock fragments are common, coarse gravel and stones, weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, clay coatings; no roots. 214 Appendix 23. Profile VI/YC/CT1: Classification: Haplic Regosol (Skeletic) Date of description: 02.03.2011 Location: Din Tri village, Chieng Tuong commune, Yen Chau district, Son La province Longitude: 0435247 Latitude: 2303834 Altitude: 1265m Parent rock: volcanic (VO3) Slope inclination: approximately 310 Slope aspect: 150 Slope position: upper slope Slope form: Straight-Straight (SS) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–15 Brown (10 YR 4/2.5); clay loam texture; very fine to fine granular structure; rock fragments are common and mostly fine and medium gravel and angular, fresh or slightly weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; clear boundary to Bt1. BtC1 15–40 Yellowish brown (10 YR 4.5/4); clay loam texture; subangular blocky structure; rock fragments are abundant and from fine to coarse gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; no presence of CaCO3; common and faint coatings, humus and clay coatings; very fine and fine roots; gradual boundary to Bt2. BtC2 40–80 Yellowish brown (10 YR 5/4); clay texture; subangular blocky structure; rock fragments are very few, fine to coarse gravel and angular, fresh or slightly weathered; friable moist; sticky and plastic; no presence of CaCO3; few and faint coatings, clay coatings; no roots; diffuse boundary to Bt3. C 80–130 Hard bed rock, boulders to large boulders, fresh. Appendix 215 24. Profile VI/YC/CT2: Classification: Cutanic Alisol (Clayic Chromic) Date of description: 04.03.2011 Location: Din Tri village, Chieng Tuong commune, Yen Chau district, Son La province Longitude: 0435241 Latitude: 2304005 Altitude: 1186m Parent rock: volcanic (VO3) Slope inclination: approximately 240 Slope aspect: 3500 Slope position: middle slope Slope form: Convex-Convex (VV) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–15 Brownish black (7.5 YR 4/2.5); clay loam texture; very fine to fine granular structure; rock fragments are few and mostly fine gravel and angular, fresh or slightly weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; abrupt boundary to Bt1. Bt 15–50 Brown (10 YR 4/4); clay texture; subangular blocky structure; rock fragments are common and from fine to coarse gravel and angular, weathered; friable moist; sticky and plastic; no presence of CaCO3; common and faint coatings, humus and clay coatings; very fine and fine roots; gradual boundary to Bt2. CBt 50–90 Dull brown (7.5 YR 5/6); clay texture; subangular blocky structure; rock fragments are many, medium gravel to boulders and angular, weathered; friable moist; sticky and plastic; no presence of CaCO3; few and faint coatings, clay coatings; no roots; diffuse boundary to Bt3. BtC 90–140 Dull brown (7.5 YR 5/6); clay texture; subangular blocky structure; rock fragments are abundant, stones to boulders, weathered; friable moist; sticky and plastic; fine and fine pores are common, few medium pores; no presence of CaCO3; abundant and faint coatings, clay coatings; no roots. 216 Appendix 25. Profile VI/YC/CT3: Classification: Cutanic Alisol (Clayic Skeletic) Date of description: 14.04.2011 Location: Din Tri village, Chieng Tuong commune, Yen Chau district, Son La province Longitude: 0435232 Latitude: 2304113 Altitude: 1146m Parent rock: volcanic (VO3) Slope inclination: approximately 270 Slope aspect: 300 Slope position: upper foot slope Slope form: Convex-Convex (SS) Land-use: Maize Profile description: Horizon Depth (cm) Description Ap 0–10 Brown (10 YR 4/2.5); clay loam texture; very fine to fine granular structure; rock fragments are few and fine to medium gravel and angular, weathered; very friable moist; slightly sticky and slightly plastic; very fine and fine pores are common, few medium pores; no presence of CaCO3; no coatings; very fine and fine roots are commonly seen; abrupt boundary to BtC. CBt 10–30 Brown (10 YR 4/4); clay texture; subangular blocky structure; rock fragments are abundant and from fine gravel to stones and angular, weathered; friable moist; sticky and plastic; no presence of CaCO3; common and faint coatings, clay coatings; no roots; diffuse boundary to CBt. BtC 30–110 Dull brown (7.5 YR 4.5/6); clay texture; subangular blocky structure; rock fragments are dominant, medium gravel to large boulders, weathered; friable moist; sticky and plastic; no presence of CaCO3; few and faint coatings, clay coatings; no roots. Appendix 9.3. Soil properties calculations for the Yen Chau SOTER database 217 Figure 9.1. Major physical and chemical properties of the soil profiles in the Yen Chau SOTER database 218 Appendix Figure 9.2. An example of the calculation of physical and chemical soil quality indices Appendix 219 220 Appendix 1.1.25.53 (left to right) = order of the profile in these charts, = order of the profile in the SOTER database above, 25 = slope form of the profile, 53 = slope inclination in % of the profile Figure 9.3b. Soil horizon thicknesses within 0-100cm of the soil profiles that have pH values (unit of y-axis: cm) 1.25.53 (left to right) = order of the profile in the SOTER data base in Annex???, 25 = slope form of the profile, 53 = slope inclination in % of the profile Figure 9.3a. Soil horizon thicknesses within 0-100cm of the soil profiles in the SOTER database (unit of y-axis: cm) K2yC1 Appendix 221 Topsoil (cm) 10 15 20 25 30 VO1 SO Ap K2yC2 Ah VO2 VO3 BtAh SO AhBt SC Bt CBt ALISOLS OM topsoil K2yC2 K2yC1 Figure 9.4. SOM content in relation with A-horizon thickness in the topsoil SC LUVISOLS CA RE VE QA V1K2V1V2V3SO K2 S S SK2 STA PHALEGLE 1.25.53 2.11.45 3.6.53 4.10.51 5.14.53 6.5.68 7.25.73 8.13.49 9.10.51 10.6.36 11.6.48 12.6.46 13.6.48 14.6.47 15.15.47 16.21.36 17.23.47 18.14.31 19.12.27 20.24.45 21.24.49 22.12.34 23.19.53 24.28.39 25.6.15 26.15.58 27.14.41 28.1.12 29.6.47 30.6.49 31.15.51 32.15.36 33.18.42 34.17.45 35.24.36 36.24.51 37.24.34 38.14.60 39.6.38 40.11.51 41.10.34 42.23.49 43.19.47 44.28.53 45.15.44 46.24.49 47.15.47 48.15.38 49.6.27 50.15.49 51.16.58 52.15.51 53.16.55 54.16.45 55.18.49 56.15.47 57.16.67 59.19.42 60.10.31 61.10.38 62.19.38 63.28.70 64.9.49 65.25.64 66.5.53 67.15.46 68.15.50 69.16.65 70.21.12 71.29.9 72.6.27 73.13.51 74.24.38 75.29.16 76.15.81 77.13.25 78.24.12 79.29.7 80.15.5 81.16.5 82.17.49 83.18.51 84.6.60 85.18.49 86.29.3 87.15.45 88.15.52 89.15.54 90.18.47 91.9.42 92.18.29 93.6.53 94.6.58 95.25.25 96.14.31 97.1.9 98.1.12 99.19.51 100.19.49 101.19.58 102.19.63 106.15.43 107.15.45 108.15.27 109.18.38 110.19.29 111.24.34 112.6.42 113.24.65 114.24.84 115.1.19 116.29.6 10 15 20 25 30 SOM content (kg/m2) 222 Appendix Acknowledgement 223 Acknowledgement Firstly, I wish to thank the German Science Foundation (DFG) for the financial support within the framework of the SFB 564 “Research for sustainable land use and rural development in mountainous regions of Southeast Asia”. I would like to express my deep gratitude to Prof. Dr. Karl Stahr for accepting me as his PhD student and for supervising me throughout my research period with kind support, understanding, encouragement, and wonderful ideas to improve my works. Thanks go to Dr. Gerhard Clemens for sharing his valuable experience, knowledge, and advice for my fieldwork and indoor works during and after his active time in the Uplands Program in Vietnam. My grateful thanks go to Dr. Volker Häring and Dr. Nguyen Dinh Cong for sharing their data and for useful discussions with Dr. Volker Häring. Thanks go to field assistants Do Van Hung, Nguyen Van Thach, Nguyen Huu Thuy for their assistance, and to my long-term local field assistants and friends Lo Van Ha, Hoang Van Vui. Without your hardwork and friendly company, my fieldwork would have been very difficult and tedious. My thankful expression goes to the local authorities of Yen Chau district and communes where my field observations were carried out for accepting me in the areas and providing with valuable map and relevant information. Special thanks go to Dr. Ludger Herrmann and Andrea Zipp their help with laboratory analyses. Great appreciation also goes to Bachelor and Master students working in B4.1 and B4.2 subprojects for sharing their well prepared data. Last but not least, I am deeply indebted to the support of my family. I deeply thank my beloved parents for their great encouragement and support, and my dearest wife who tolerated my long absences, for all of her sacrifices during the periods not having me around, and for her love, understanding, and all of the encouragements. Deepest thanks and love go to my children, who were born during my research. With your presence, my life has become more meaningful than ever and this encouraged me a lot in producing this best work that I could [...]... regional scale in Brazil Graef and Stahr (2000) used the SOTER approach for management of soil, terrain, and land use and vegetation data at regional scale Herrmann et al (2001) applied SOTER as a tool for land use planning in West Africa at a scale of 1:200.000 Graef et al (2002) developed a SOTER database in Niger for improving soil and water conservation measures Igué (2000) and Igué et al (2004)... terrain database consists of information of soils and terrain characteristics in a Relational Database Management System (RDBMS) linked with a Geographic Information System (GIS) SOTER is where information of terrain and soils is stored, and where each map unit representing a distinctive combination of landform/terrain, parent materials and soil information is defined The GIS package is a tool to spatially... mitigating environmental impacts, and maintaining environmental conservation From this fact, a Methodology for a World Soils and Terrain Digital Database (SOTER) was developed at the International Soil Reference and Information Centre (ISRIC), based in Wageningen, the Netherlands, in 1987 The original idea and premise of SOTER were developed in Russia and Germany to map land characteristics based on interactions... group A, having the central property values of soil class A, V1 A and V 2A (Figure 2.7b) These pieces of information are then deviated from reality, leading to false soil information achieved and incorrectly spatially delineated later on the map Spatial generalization is a process of delineating soil polygon areas geographically and spatially onto a map This process involves map scales and mapping techniques... interactions among physical, chemical, biological and social phenomena over time (van Engelen, 1995) SOTER studies land through distinctive combinations of soils and terrain characteristics such as landform, surface form, slope, and parent material Each combination represents a SOTER unit Data in the SOTER database are organized in:   A relational data base, which consists of attribute data of soil-related... transforming and displaying spatial data from the real world” (Burrough, 1986)  a database system in which most of the data are spatially indexed, and upon which a set of procedures operated in order to answer queries about spatial entities in the database” (Smith et al., 1987)  a system that consists of computer software, hardware, and peripherals that transform geographically referenced spatial data into... Environment of VietNam, land- use planning at district and provincial level is implemented every 5 consecutive years The land- use map of Yen Chau was obtained on the completion for 2011 from the Department of Natural Resources and Environment of Son La province Most landuse maps in Vietnam were created from aerial photos and get updated periodically by the 10 Methodology network of cadastre offices and officers... a mountainous district of northern Vietnam, at a scale of 1:25.000 SOTER units reveal unique combinations of soils and terrain characteristics and they can be mapped The information of these units can be stored in two ways: geometry and attribute data in which an attribute characterizes an object or a geometric shape Geometry data are stored in a Geographic Information System (GIS) Attribute data are... 10 m is rather small and used for making maps at large scales only, meaning mapping small areas At smaller scales, much larger area to be mapped, the spatial resolution increases (ex 30 m by 30 m or higher), making a conventional soil map not able to describe information of areas smaller than this cell size Soil information of these small areas is then ignored and included into more dominant soil groups... developed a SOTER database for Central Benin at a scale of 1:50.000 Schuler et al (2010) and Cong (2011) created SOTER databases for small catchments with area ranging from 4-10 km2 at a scale of 1:10.000 Igué et al (2014) studied 6 Methodology the variability of physical and chemical soil characteristics in relation with landscape in Benin using the SOTER approach This research will develop a SOTER database . Vinh Towards sustainability of land use in a highly vulnerable and degraded tropical soil landscape of northern Vietnam – bridging scales Auf dem Weg zu einer nachhaltigen Landnutzung in. SOTER approach for estimating yield potentials at regional scale in Brazil. Graef and Stahr (2000) used the SOTER approach for management of soil, terrain, and land use and vegetation data at. INSTITUTE OF SOIL SCIENCE AND LAND EVALUATION UNIVERSITY OF HOHENHEIM Soil Science and Petrography Unit Prof. Dr. Karl Stahr Towards sustainability of land use in a highly vulnerable and